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1
Laudencia-Chingcuanco, Debbie y Sarah Hake. "The indeterminate floral apex1 gene regulates meristem determinacy and identity in the maize inflorescence". Development 129, n.º 11 (1 de junio de 2002): 2629–38. http://dx.doi.org/10.1242/dev.129.11.2629.
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Meristems may be determinate or indeterminate. In maize, the indeterminate inflorescence meristem produces three types of determinate meristems: spikelet pair, spikelet and floral meristems. These meristems are defined by their position and their products. We have discovered a gene in maize, indeterminate floral apex1 (ifa1) that regulates meristem determinacy. The defect found in ifa1 mutants is specific to meristems and does not affect lateral organs. In ifa1 mutants, the determinate meristems become less determinate. The spikelet pair meristem initiates more than a pair of spikelets and the spikelet meristem initiates more than the normal two flowers. The floral meristem initiates all organs correctly, but the ovule primordium, the terminal product of the floral meristem, enlarges and proliferates, expressing both meristem and ovule marker genes. A role for ifa1 in meristem identity in addition to meristem determinacy was revealed by double mutant analysis. In zea agamous1 (zag1) ifa1 double mutants, the female floral meristem converts to a branch meristem whereas the male floral meristem converts to a spikelet meristem. In indeterminate spikelet1 (ids1) ifa1 double mutants, female spikelet meristems convert to branch meristems and male spikelet meristems convert to spikelet pair meristems. The double mutant phenotypes suggest that the specification of meristems in the maize inflorescence involves distinct steps in an integrated process.
2
Kong, Doudou y Annette Becker. "Then There Were Plenty-Ring Meristems Giving Rise to Many Stamen Whorls". Plants 10, n.º 6 (3 de junio de 2021): 1140. http://dx.doi.org/10.3390/plants10061140.
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Floral meristems are dynamic systems that generate floral organ primordia at their flanks and, in most species, terminate while giving rise to the gynoecium primordia. However, we find species with floral meristems that generate additional ring meristems repeatedly throughout angiosperm history. Ring meristems produce only stamen primordia, resulting in polystemous flowers (having stamen numbers more than double that of petals or sepals), and act independently of the floral meristem activity. Most of our knowledge on floral meristem regulation is derived from molecular genetic studies of Arabidopsis thaliana, a species with a fixed number of floral organs and, as such of only limited value for understanding ring meristem function, regulation, and ecological value. This review provides an overview of the main molecular players regulating floral meristem activity in A. thaliana and summarizes our knowledge of ring primordia morphology and occurrence in dicots. Our work provides a first step toward understanding the significance and molecular genetics of ring meristem regulation and evolution.
3
Fletcher, J. C. "The ULTRAPETALA gene controls shoot and floral meristem size in Arabidopsis". Development 128, n.º 8 (15 de abril de 2001): 1323–33. http://dx.doi.org/10.1242/dev.128.8.1323.
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The regulation of proper shoot and floral meristem size during plant development is mediated by a complex interaction of stem cell promoting and restricting factors. The phenotypic effects of mutations in the ULTRAPETALA gene, which is required to control shoot and floral meristem cell accumulation in Arabidopsis thaliana, are described. ultrapetala flowers contain more floral organs and whorls than wild-type plants, phenotypes that correlate with an increase in floral meristem size preceding organ initiation. ultrapetala plants also produce more floral meristems than wild-type plants, correlating with an increase in inflorescence meristem size without visible fasciation. Expression analysis indicates that ULTRAPETALA controls meristem cell accumulation partly by limiting the domain of CLAVATA1 expression. Genetic studies show that ULTRAPETALA acts independently of ERA1, but has overlapping functions with PERIANTHIA and the CLAVATA signal transduction pathway in controlling shoot and floral meristem size and meristem determinacy. Thus ULTRAPETALA defines a novel locus that restricts meristem cell accumulation in Arabidopsis shoot and floral meristems.
4
Souer, E., A. van der Krol, D. Kloos, C. Spelt, M. Bliek, J. Mol y R. Koes. "Genetic control of branching pattern and floral identity during Petunia inflorescence development". Development 125, n.º 4 (15 de febrero de 1998): 733–42. http://dx.doi.org/10.1242/dev.125.4.733.
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A main determinant of inflorescence architecture is the site where floral meristems are initiated. We show that in wild-type Petunia bifurcation of the inflorescence meristem yields two meristems of approximately equal size. One terminates into a floral meristem and the other maintains its inflorescence identity. By random transposon mutagenesis we have generated two mutants in which the architecture of the inflorescence is altered. In the extra petals- (exp) mutant the inflorescence terminates with the formation of a single terminal flower. Phenotypic analysis showed that exp is required for the bifurcation of inflorescence meristems. In contrast, the aberrant leaf and flower- (alf) mutant is affected in the specification of floral meristem identity while the branching pattern of the inflorescence remains unaltered. A weak alf allele was identified that, after bifurcation of the inflorescence meristem, yields a ‘floral’ meristem with partial inflorescence characteristics. By analysing independent transposon dTph1 insertion alleles we show that the alf locus encodes the Petunia FLORICAULA/LEAFY homolog. In situ hybridisation shows that alf is expressed in the floral meristem and also in the vegetative meristem. Differences and similarities between these Petunia mutants and mutations affecting inflorescence architecture in other species will be discussed.
5
Grbić, Vojislava. "Comparative analysis of axillary and floral meristem development". Canadian Journal of Botany 83, n.º 4 (1 de abril de 2005): 343–49. http://dx.doi.org/10.1139/b05-017.
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Axillary and floral meristems are shoot meristems that initiate postembryonically. In Arabidopsis, axillary meristems give rise to branches during vegetative development while floral meristems give rise to flowers during reproductive development. This review compares the development of these meristems from their initiation at the shoot apical meristem up to the establishment of their specific developmental fates. Axillary and floral meristems originate from lateral primordia that form at flanks of the shoot apical meristem. Initial development of vegetative and reproductive primordia are similar, resulting in the formation of a morphologically defined primordium partitioned into adaxial and abaxial domains. The adaxial primordial domain is competent to form a meristem, while the abaxial domain correlates with the formation of a leaf. This review proposes that all primordia partition into domains competent to form the meristem and the leaf. According to this model, a vegetative primordium develops as leaf-bias while a reproductive primordium develops as meristem-bias.Key words: SHOOTMERISTEMLESS, LATERAL SUPPRESSOR, AINTEGUMENTA, adaxial primordial domain, abaxial primordial domain, shoot morphogenesis.
6
Thiel, J., R. Koppolu, C. Trautewig, C. Hertig, S. M. Kale, S. Erbe, M. Mascher et al. "Transcriptional landscapes of floral meristems in barley". Science Advances 7, n.º 18 (abril de 2021): eabf0832. http://dx.doi.org/10.1126/sciadv.abf0832.
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Organ development in plants predominantly occurs postembryonically through combinatorial activity of meristems; therefore, meristem and organ fate are intimately connected. Inflorescence morphogenesis in grasses (Poaceae) is complex and relies on a specialized floral meristem, called spikelet meristem, that gives rise to all other floral organs and ultimately the grain. The fate of the spikelet determines reproductive success and contributes toward yield-related traits in cereal crops. Here, we examined the transcriptional landscapes of floral meristems in the temperate crop barley (Hordeum vulgare L.) using RNA-seq of laser capture microdissected tissues from immature, developing floral structures. Our unbiased, high-resolution approach revealed fundamental regulatory networks, previously unknown pathways, and key regulators of barley floral fate and will equally be indispensable for comparative transcriptional studies of grass meristems.
7
Loehrlein, Marietta y Richard Craig. "Floral Ontogeny of Pelargonium ×domesticum". Journal of the American Society for Horticultural Science 125, n.º 1 (enero de 2000): 36–40. http://dx.doi.org/10.21273/jashs.125.1.36.
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Floral ontogeny of two cultivars of Pelargonium ×domesticum L.H. Bailey, (regal pelargonium) `Duchess' and `Jennifer', was examined. Plants of both cultivars were grown together in a growth chamber at 15.5 °C with a photosynthetic photon flux of 10 mol·m-2·d-1. Meristems were examined at 5-day intervals over an experimental period of 170 days. The initial vegetative meristem was convex with leaf primordia initiated on either side in an alternate pattern. Early floral initiation was characterized by formation of two clefts on either side of the meristem. Between the clefts new meristems developed. Proliferation of meristems continued until numerous meristems were organized in a cluster arrangement at the apex of the shoot. New meristems lacked leaf primordia and would develop into flowers. Floral organ primordia on a floral meristem were initiated in a succession of four whorls: sepals, petals, androecia, and gynoecium.
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Wei, Wei, Robert E. Davis, Gary R. Bauchan y Yan Zhao. "New Symptoms Identified in Phytoplasma-Infected Plants Reveal Extra Stages of Pathogen-Induced Meristem Fate-Derailment". Molecular Plant-Microbe Interactions® 32, n.º 10 (octubre de 2019): 1314–23. http://dx.doi.org/10.1094/mpmi-01-19-0035-r.
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In flowering plants, the transition of a shoot apical meristem from vegetative to reproductive destiny is a graduated, multistage process that involves sequential conversion of the vegetative meristem to an inflorescence meristem, initiation of floral meristems, emergence of flower organ primordia, and formation of floral organs. This orderly process can be derailed by phytoplasma, a bacterium that parasitizes phloem sieve cells. In a previous study, we showed that phytoplasma-induced malformation of flowers reflects stage-specific derailment of shoot apical meristems from their genetically preprogrammed reproductive destiny. Our current study unveiled new symptoms of abnormal morphogenesis, pointing to derailment of meristem transition at additional stages previously unidentified. We also found that the fate of developing meristems may be derailed even after normal termination of the floral meristem and onset of seed production. Although previous reports by others have indicated that different symptoms may be induced by different phytoplasmal effectors, the phenomenon observed in our experiment raises interesting questions as to (i) whether effectors can act at specific stages of meristem transition and (ii) whether specific floral abnormalities are attributable to meristem fate-derailment events triggered by different effectors that each act at a specific stage in meristem transition. Research addressing such questions may lead to discoveries of an array of phytoplasmal effectors.
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Clark, S. E., M. P. Running y E. M. Meyerowitz. "CLAVATA3 is a specific regulator of shoot and floral meristem development affecting the same processes as CLAVATA1". Development 121, n.º 7 (1 de julio de 1995): 2057–67. http://dx.doi.org/10.1242/dev.121.7.2057.
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We have previously described the phenotype of Arabidopsis thaliana plants with mutations at the CLAVATA1 (CLV1) locus (Clark, S. E., Running, M. P. and Meyerowitz, E. M. (1993) Development 119, 397–418). Our investigations demonstrated that clv1 plants develop enlarged vegetative and inflorescence apical meristems, and enlarged and indeterminate floral meristems. Here, we present an analysis of mutations at a separate locus, CLAVATA3 (CLV3), that disrupt meristem development in a manner similar to clv1 mutations. clv3 plants develop enlarged apical meristems as early as the mature embryo stage. clv3 floral meristems are also enlarged compared with wild type, and maintain a proliferating meristem throughout flower development. clv3 root meristems are unaffected, indicating that CLV3 is a specific regulator of shoot and floral meristem development. We demonstrate that the strong clv3-2 mutant is largely epistatic to clv1 mutants, and that the semi- dominance of clv1 alleles is enhanced by double heterozygosity with clv3 alleles, suggesting that these genes work in the same pathway to control meristem development. We propose that CLV1 and CLV3 are required to promote the differentiation of cells at the shoot and floral meristem.
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Laux, T., K. F. Mayer, J. Berger y G. Jurgens. "The WUSCHEL gene is required for shoot and floral meristem integrity in Arabidopsis". Development 122, n.º 1 (1 de enero de 1996): 87–96. http://dx.doi.org/10.1242/dev.122.1.87.
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Self perpetuation of the shoot meristem is essential for the repetitive initiation of shoot structures during plant development. In Arabidopsis shoot meristem maintenance is disrupted by recessive mutations in the WUSCHEL (WUS) gene. The defect is evident at all developmental stages and is restricted to shoot and floral meristems, whereas the root meristem is not affected. wus mutants fail to properly organize a shoot meristem in the embryo. Postembryonically, defective shoot meristems are initiated repetitively but terminate prematurely in aberrant flat structures. In contrast to wild-type shoot meristems, primordia initiation occurs ectopically across mutant apices, including the center, and often new shoot meristems instead of organs are initiated. The cells of wus shoot apices are larger and more vacuolated than wild-type shoot meristem cells. wus floral meristems terminate prematurely in a central stamen. Double mutant studies indicate that the number of organ primordia in the center of wus flowers is limited, irrespective of organ identity and we propose that meristem cells are allocated into floral whorl domains in a sequential manner. WUS activity also appears to be required for the formation of supernumerary organs in the center of agamous, superman or clavata1 flowers, suggesting that the WUS gene acts upstream of the corresponding genes. Our results suggest that the WUS gene is specifically required for central meristem identity of shoot and floral meristems to maintain their structural and functional integrity.
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Ratcliffe, O. J., D. J. Bradley y E. S. Coen. "Separation of shoot and floral identity in Arabidopsis". Development 126, n.º 6 (15 de marzo de 1999): 1109–20. http://dx.doi.org/10.1242/dev.126.6.1109.
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The overall morphology of an Arabidopsis plant depends on the behaviour of its meristems. Meristems derived from the shoot apex can develop into either shoots or flowers. The distinction between these alternative fates requires separation between the function of floral meristem identity genes and the function of an antagonistic group of genes, which includes TERMINAL FLOWER 1. We show that the activities of these genes are restricted to separate domains of the shoot apex by different mechanisms. Meristem identity genes, such as LEAFY, APETALA 1 and CAULIFLOWER, prevent TERMINAL FLOWER 1 transcription in floral meristems on the apex periphery. TERMINAL FLOWER 1, in turn, can inhibit the activity of meristem identity genes at the centre of the shoot apex in two ways; first by delaying their upregulation, and second, by preventing the meristem from responding to LEAFY or APETALA 1. We suggest that the wild-type pattern of TERMINAL FLOWER 1 and floral meristem identity gene expression depends on the relative timing of their upregulation.
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McSteen, Paula y Sarah Hake. "barren inflorescence2 regulates axillary meristem development in the maize inflorescence". Development 128, n.º 15 (1 de agosto de 2001): 2881–91. http://dx.doi.org/10.1242/dev.128.15.2881.
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Organogenesis in plants is controlled by meristems. Shoot apical meristems form at the apex of the plant and produce leaf primordia on their flanks. Axillary meristems, which form in the axils of leaf primordia, give rise to branches and flowers and therefore play a critical role in plant architecture and reproduction. To understand how axillary meristems are initiated and maintained, we characterized the barren inflorescence2 mutant, which affects axillary meristems in the maize inflorescence. Scanning electron microscopy, histology and RNA in situ hybridization using knotted1 as a marker for meristematic tissue show that barren inflorescence2 mutants make fewer branches owing to a defect in branch meristem initiation. The construction of the double mutant between barren inflorescence2 and tasselsheath reveals that the function of barren inflorescence2 is specific to the formation of branch meristems rather than bract leaf primordia. Normal maize inflorescences sequentially produce three types of axillary meristem: branch meristem, spikelet meristem and floral meristem. Introgression of the barren inflorescence2 mutant into genetic backgrounds in which the phenotype was weaker illustrates additional roles of barren inflorescence2 in these axillary meristems. Branch, spikelet and floral meristems that form in these lines are defective, resulting in the production of fewer floral structures. Because the defects involve the number of organs produced at each stage of development, we conclude that barren inflorescence2 is required for maintenance of all types of axillary meristem in the inflorescence. This defect allows us to infer the sequence of events that takes place during maize inflorescence development. Furthermore, the defect in branch meristem formation provides insight into the role of knotted1 and barren inflorescence2 in axillary meristem initiation.
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Running, M. P., J. C. Fletcher y E. M. Meyerowitz. "The WIGGUM gene is required for proper regulation of floral meristem size in Arabidopsis". Development 125, n.º 14 (15 de julio de 1998): 2545–53. http://dx.doi.org/10.1242/dev.125.14.2545.
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The study of cell division control within developing tissues is central to understanding the processes of pattern formation. The floral meristem of angiosperms gives rise to floral organs in a particular number and pattern. Despite its critical role, little is known about how cell division is controlled in the floral meristem, and few genes involved have been identified. We describe the phenotypic effects of mutations in WIGGUM, a gene required for control of cell proliferation in the floral and apical meristem of Arabidopsis thaliana. wiggum flowers contain more organs, especially sepals and petals, than found in wild-type flowers. This organ number phenotype correlates with specific size changes in the early floral meristem, preceding organ initiation. Genetic studies suggest that WIGGUM acts on a similar process but in a separate pathway than the CLAVATA1 and CLAVATA3 genes in meristem size regulation, and reveal interactions with other genes affecting meristem structure and identity. Analysis of double mutant phenotypes also reveals a role for WIGGUM in apical meristem function. We propose that WIGGUM plays a role in restricting cell division relative to cellular differentiation in specific regions of the apical and floral meristems.
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Parcy, François, Kirsten Bomblies y Detlef Weigel. "Interaction of LEAFY, AGAMOUS and TERMINAL FLOWER1 in maintaining floral meristem identity in Arabidopsis". Development 129, n.º 10 (15 de mayo de 2002): 2519–27. http://dx.doi.org/10.1242/dev.129.10.2519.
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The Arabidopsis transcription factor LEAFY acts upstream of homeotic genes such as AGAMOUS to confer floral identity on meristems that arise after the transition to reproductive development. Compared to the genetic circuitry regulating the establishment of floral meristem identity, little is known about its maintenance. Previous experiments with leafy heterozygous plants and agamous mutants grown in conditions that reduce the floral inductive stimulus have shown that both genes are required to prevent reversion of floral to inflorescence meristems. Here, we present evidence that LEAFY maintains floral meristem identity independently of AGAMOUS, and that the primary role of LEAFY is either direct repression of shoot identity genes or repression of an intermediate factor that activates shoot identity genes. The latter conclusions were deduced from the phenotypes conferred by a gain-of-function transgene, LEAFY:VP16, that appears to act as a dominant negative, or antimorphic, allele during maintenance of floral meristem identity. These observations contrast with previous findings that LEAFY acts as a direct activator of floral homeotic genes, supporting the hypothesis that the transcriptional activity of LEAFY is dependent on specific co-regulators.
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Linh, Tran Minh Hong, Trinh Cam Tu, Bui Trang Viet y Tran Thanh Huong. "Roles of plant growth regulators in the in vitro floral organogenesis of rose (Rosa hybrida L.)". Science and Technology Development Journal - Natural Sciences 2, n.º 6 (10 de octubre de 2019): 98–104. http://dx.doi.org/10.32508/stdjns.v2i6.849.
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In this study, morphological and physiological changes in flower development of the rose (Rosa hybrida L.) in the garden were analyzed. Role of plant growth regulators on in vitro floral organogenesis of rose from floral meristem was investigated. The flowering of Rosa hybrida L. has three phases: shoot apical meristem, single floral meristem and floral bud with sepals, petals, stamens and gynoecium. Activities of cytokinins and auxins increased in the transition of shoots from vegetative growth to floral initiation stage. Floral meristems having sepals and the first layer of petals on MS medium with 0.5 mg/L GA3, 0.1 mg/L NAA and 0.3 m/L BA were continuously developed in these next layers of petals and became floral buds at the highest percentage after 4 and 8 weeks of culture, respectively.
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Loehrlein, Marietta M. y Richard Craig. "Floral Ontogeny of Pelargonium × domesticum". HortScience 33, n.º 3 (junio de 1998): 537a—537. http://dx.doi.org/10.21273/hortsci.33.3.537a.
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Floral ontogeny of Pelargonium xdomesticum was examined for two cultivars grown under identical environmental conditions. Apical meristems of `Duchess' and `Jennifer' were vegetative at the commencement of the experiment. Meristems were examined every five days over an experimental period lasting 85 days. Floral ontogeny was the same for both cultivars, although the timing of floral initiation of the meristem, floral organ initiation, and floral organ development differed. The vegetative meristem was convex with leaf primordia initiated on either side in an alternate pattern. Early floral initiation was characterized by formation of a cleft towards one side of the meristem, followed quickly by a second cleft on the other side. Between the clefts new meristems developed. New meristems lacked leaf primordia. Proliferation of meristems continued until numerous meristems were organized in a cluster arrangement at the apex of the shoot. Proliferation of meristems at the apex continued until multiple inflorescences had developed. Inflorescences were subtended by bracts. Floral organ primordia were initiated in a succession of four whorls: sepals, petals, androecia and gynoecium. Petals and androecia appeared to develop simultaneously soon after sepal primordia were visible. Petal primordia remained small while the androecia continued to grow. The gynoecium first formed a conical shape, with carpels protruding from the base in a bulbous fashion. At the distal end of the gynoecium, divisions appeared which developed into stigmatic lobes. As the gynoecium elongated, stigmatic lobes became more pronounced. Petal elongation concurred in synchrony with elongation of the gynoecium. On one experimental unit of `Duchess' two florets had opened at 750 total cumulative moles. No `Jennifer' florets had opened by termination of the experiment.
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Evans, Michael R., Harold F. Wilkins y Wesley P. Hackett. "Meristem Ontogenetic Age as the Controlling Factor in Long-day Floral Initiation in Poinsettia". Journal of the American Society for Horticultural Science 117, n.º 6 (noviembre de 1992): 961–65. http://dx.doi.org/10.21273/jashs.117.6.961.
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The poinsettia [Euphorbia pulcherrima (Willd. ex. Klotzsch)] is a short-day plant (SDP) for floral initiation that will also initiate floral structures (cyathia) under long days (LD) after the apical meristem produces a cultivar-dependent number of nodes (long-day node number). Leaf removal, root restriction, and air layering failed to affect the long-day node number (LDNN) of the apical meristem. Repeated rooting of shoots, which resulted in the removal of nodes, did not affect the total number of nodes initiated by the apical meristem before floral initiation, although the number of nodes intact on the plant at the time of floral initiation was reduced. Reciprocal grafting of axillary buds of `Eckespoint Lilo' and `Gutbier V-14 Glory' plants did not affect the LDNN of the grafted meristem since the LDNN was the same as for nongrafted buds of the same cultivar. Further, grafting axillary buds from different positions along the main axis that differed in LDNN did not affect the LDNN of the grafted meristems. On the basis of these results, it was concluded that LD floral initiation in poinsettia is a function of the ontogenetic age of the meristem and that the LDNN represents a critical ontogenetic age for floral initiation to occur under LD.
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Pouteau, S., D. Nicholls, F. Tooke, E. Coen y N. Battey. "The induction and maintenance of flowering in Impatiens". Development 124, n.º 17 (1 de septiembre de 1997): 3343–51. http://dx.doi.org/10.1242/dev.124.17.3343.
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The mechanisms that establish the floral meristem are now becoming clearer, but the way in which flowering is maintained is less well understood. Impatiens balsamina provides a unique opportunity to address this question because reversion to vegetative growth can be obtained in a predictable way by transferring plants from inductive to non-inductive conditions. Following increasing amounts of induction, reversion takes place at progressively later stages of flower development. Partial flower induction and defoliation experiments show that a floral signal is produced in the cotyledon in response to inductive conditions and that this signal progressively diminishes after transfer to non-inductive conditions, during reversion. Therefore reversion in Impatiens is most likely due to the failure of leaves to become permanent sources of inductive signal in addition to the lack of meristem commitment to flowering. Analysis of the expression of the Impatiens homologues of the meristem identity genes floricaula and squamosa indicates that a change in floricaula transcription is not associated with the establishment or maintenance of the floral meristem in this species. Squamosa transcription is associated with floral development and petal initiation, and is maintained in existing petal or petaloid primordia even after the meristem has reverted. However, it is not expressed in the reverted meristem, in which leaves are initiated in whorled phyllotaxis and without axillary meristems, both characteristics usually associated with the floral meristem. These observations show that squamosa expression is not needed for the maintenance of these floral characters. The requirement for the production of the floral signal in the leaf during the process of flower development may reflect an additional function separate to that of squamosa activation; alternatively the signal may be required to ensure continued transcriptional activation in the meristem.
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Clark, S. E., M. P. Running y E. M. Meyerowitz. "CLAVATA1, a regulator of meristem and flower development in Arabidopsis". Development 119, n.º 2 (1 de octubre de 1993): 397–418. http://dx.doi.org/10.1242/dev.119.2.397.
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We have investigated the effects on plant development of mutations in the Arabidopsis thaliana CLAVATA1 gene. In clavata1 plants, vegetative, inflorescence and floral meristems are all enlarged relative to wild type. The apical meristem can fasciate in the more severe mutant alleles, and this fasciation can occur prior to the transition to flowering. Flowers of clavata1 plants can have increased numbers of organs in all four whorls, and can also have additional whorls not present in wild-type flowers. Double mutant combinations of clavata1 with agamous, apetala2, apetala3 and pistillata indicate that CLAVATA1 controls the underlying floral meristem structure upon which these homeotic genes act. Double mutant combinations of clavata1 with apetala1 and leafy indicate CLAVATA1 plays a role in establishing and maintaining floral meristem identity, in addition to its role in controlling meristem size. In support of this, RNA expression patterns of AGAMOUS and APETALA1 are altered in clavata1 flowers.
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Clark, S. E., S. E. Jacobsen, J. Z. Levin y E. M. Meyerowitz. "The CLAVATA and SHOOT MERISTEMLESS loci competitively regulate meristem activity in Arabidopsis". Development 122, n.º 5 (1 de mayo de 1996): 1567–75. http://dx.doi.org/10.1242/dev.122.5.1567.
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The CLAVATA (CLV1 and CLV3) and SHOOT MERISTEMLESS (STM) genes specifically regulate shoot meristem development in Arabidopsis. CLV and STH appear to have opposite functions: c1v1 and Clv3 mutants accumulate excess undifferentiated cells in the shoot and floral meristem, while stm mutants fail to form the undifferentiated cells of the shoot meristem during embryonic development. We have identified a weak allele of stm (stm-2) that reveals STM is not only required for the establish- ment of the shoot meristem, but is also required for the continued maintenance of undifferentiated cells in the shoot meristem and for proper proliferation of cells in the floral meristem. We have found evidence of genetic interactions between the CLV and STM loci. clv1 and c1v3 mutations partially suppressed the stm-1 and stm-2 phenotypes, and were capable of suppression in a dominant fashion. clv stm double mutants and plants homozygous for stm but heterozygous for clv, while still lacking an embryonic shoot meristem, exhibited greatly enhanced postembryonic shoot and floral meristem development. Although stm phenotypes are recessive, stm mutations dominantly suppressed clv homozygous and heterozygous phenotypes. These results indicate that the stm phenotype is sensitive to the levels of CLV activity, while the clv phenotype is sensitive to the level of STM activity. We propose that these genes play related but opposing roles in the regulation of cell division and/or cell differentiation in shoot and floral meristems.
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Yang, Qingqing, Cunquan Yuan, Tianci Cong y Qixiang Zhang. "The Secrets of Meristems Initiation: Axillary Meristem Initiation and Floral Meristem Initiation". Plants 12, n.º 9 (4 de mayo de 2023): 1879. http://dx.doi.org/10.3390/plants12091879.
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The branching phenotype is an extremely important agronomic trait of plants, especially for horticultural crops. It is not only an important yield character of fruit trees, but also an exquisite ornamental trait of landscape trees and flowers. The branching characteristics of plants are determined by the periodic initiation and later development of meristems, especially the axillary meristem (AM) in the vegetative stage and the floral meristem (FM) in the reproductive stage, which jointly determine the above-ground plant architecture. The regulation of meristem initiation has made great progress in model plants in recent years. Meristem initiation is comprehensively regulated by a complex regulatory network composed of plant hormones and transcription factors. However, as it is an important trait, studies on meristem initiation in horticultural plants are very limited, and the mechanism of meristem initiation regulation in horticultural plants is largely unknown. This review summarizes recent research advances in axillary meristem regulation and mainly reviews the regulatory networks and mechanisms of AM and FM initiation regulated by transcription factors and hormones. Finally, considering the existing problems in meristem initiation studies and the need for branching trait improvement in horticulture plants, we prospect future studies to accelerate the genetic improvement of the branching trait in horticulture plants.
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Duclos, Denise V. y Thomas N. Björkman. "(263) Temperature Effects on Meristem Identity Genes Controlling the Reproductive Development of Cauliflower (Brassica oleracea var. botrytis) and Broccoli (Brassica oleracea var. italica)". HortScience 40, n.º 4 (julio de 2005): 1015D—1015. http://dx.doi.org/10.21273/hortsci.40.4.1015d.
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Brassica oleracea species differ in the developmental stage of their reproductive meristems at harvest. The stage that characterizes each variety depends on its genetic makeup, environment and the interaction between them. We tested a model of arrest in B. oleracea to determine functional redundancy among the paralogous genes CAL, AP1a, AP1c, FULa, FULb, FULc, and FULd; and to resolve the immediate effect of temperature on gene expression in meristems whose developmental fate is temperature regulated. By varying temperature during reproductive development, three stages of arrest were obtained: inflorescence meristem (cauliflower), floral meristem (intermediate) and floral bud (broccoli), the latter initiated by low temperature. Gene expression was measured by quantitative real time PCR (qRT-PCR). The LFY/TFL1 ratio increased as the reproductive development advanced, mainly due to decreased TFL1 expression; influenced by a dramatic increase in AP1c toward floral bud formation. The expression patterns of the FUL paralogs indicate different roles in reproductive development. FULa was more abundant in the floral primordia, while FULb, FULc, and FULd were associated with earlier arrest at the inflorescence meristem stage. The high expression of FULc and FULd at all stages of arrest differs from their homolog in Arabidopsis. High temperature reduced AP1 and LFY expression but the meristem did not revert from reproductive to vegetative. Floral bud formation in plants recessive for AP1a and CAL reaffirm that functional redundancy among some of these genes can complement the mutations. Varying temperature alone, at a fixed developmental stage, caused little variation in the expression of genes studied, causing small significant differences in TFL1 and AP1c.
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Sharman, KV, M. Sedgley y D. Aspinall. "Disruption by Temperature of Floral Evocation and Cell-Cycling in the Shoot Apical Meristem of Helipterum roseum". Functional Plant Biology 17, n.º 6 (1990): 629. http://dx.doi.org/10.1071/pp9900629.
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Flowering is inhibited in plants of Helipterum roseum grown under constant 25°C temperature conditions with a 12 h photoperiod and irradiance of 250 W m-2, but not at a constant temperature of 20°C. Floral inhibition was investigated by transferring plants between the two temperature con- ditions at different times to determine the morphological stage of inhibition, and by investigating cell-cycling at the shoot apex at the two temperatures. Floral initiation in Helipterum roseum was inhibited if the temperature increase from 20 to 25°C occurred at the doming of the apical meristem, and was delayed when the increase occurred at the initiation of involucral bracts. Steady-state cell-cycling was observed in the shoot meristem at 20°C and the cell-cycle duration was estimated at the morphological stages of large vegetative meristem, doming of the meristem and initiation of the involucral bracts. The length of the cell-cycle at these stages was 64 h, 41 h and 47 h respectively. Steady-state cell-cycling was not observed in shoot apical meristems at 25°C, and the meristem did not undergo the floral transition. It is concluded that the stage of commitment to flower is the initiation of involucral bracts, and that floral initiation is inhibited at 25°C by the loss of steady-state cell-cycling at the shoot apex.
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Jackson, D., B. Veit y S. Hake. "Expression of maize KNOTTED1 related homeobox genes in the shoot apical meristem predicts patterns of morphogenesis in the vegetative shoot". Development 120, n.º 2 (1 de febrero de 1994): 405–13. http://dx.doi.org/10.1242/dev.120.2.405.
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In this paper we describe the expression patterns of a family of homeobox genes in maize and their relationship to organogenic domains in the vegetative shoot apical meristem. These genes are related by sequence to KNOTTED1, a gene characterized by dominant neomorphic mutations which perturb specific aspects of maize leaf development. Four members of this gene family are expressed in shoot meristems and the developing stem, but not in determinate lateral organs such as leaves or floral organs. The genes show distinct expression patterns in the vegetative shoot apical meristem that together predict the site of leaf initiation and the basal limit of the vegetative ‘phytomer’ or segmentation unit of the shoot. These genes are also expressed in the inflorescence and floral meristems, where their patterns of expression are more similar, and they are not expressed in root apical meristems. These findings are discussed in relation to other studies of shoot apical meristem organization as well as possible commonality of homeobox gene function in the animal and plant kingdoms.
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Lee, Ze Hong, Takeshi Hirakawa, Nobutoshi Yamaguchi y Toshiro Ito. "The Roles of Plant Hormones and Their Interactions with Regulatory Genes in Determining Meristem Activity". International Journal of Molecular Sciences 20, n.º 16 (20 de agosto de 2019): 4065. http://dx.doi.org/10.3390/ijms20164065.
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Plants, unlike animals, have developed a unique system in which they continue to form organs throughout their entire life cycle, even after embryonic development. This is possible because plants possess a small group of pluripotent stem cells in their meristems. The shoot apical meristem (SAM) plays a key role in forming all of the aerial structures of plants, including floral meristems (FMs). The FMs subsequently give rise to the floral organs containing reproductive structures. Studies in the past few decades have revealed the importance of transcription factors and secreted peptides in meristem activity using the model plant Arabidopsis thaliana. Recent advances in genomic, transcriptomic, imaging, and modeling technologies have allowed us to explore the interplay between transcription factors, secreted peptides, and plant hormones. Two different classes of plant hormones, cytokinins and auxins, and their interaction are particularly important for controlling SAM and FM development. This review focuses on the current issues surrounding the crosstalk between the hormonal and genetic regulatory network during meristem self-renewal and organogenesis.
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Li, Fei, Wu Lan, Qin Zhou, Baojun Liu, Feng Chen, Sisi Zhang, Manzhu Bao y Guofeng Liu. "Reduced Expression of CbUFO Is Associated with the Phenotype of a Flower-Defective Cosmos bipinnatus". International Journal of Molecular Sciences 20, n.º 10 (21 de mayo de 2019): 2503. http://dx.doi.org/10.3390/ijms20102503.
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LEAFY (LFY) and UNUSUAL FLORAL ORGANS (UFO) homologous genes have been reported to play key roles in promoting the initiation of floral meristems in raceme- and cyme-type plants. Asteraceae, a large family of plants with more than 23,000 species, has a unique head-like inflorescence termed capitulum. Here, we report a floral defective plant of the garden cosmos named green head (gh), which shows homogeneous inflorescence, indistinguishable inflorescence periphery and center, and the replacement of flower meristems by indeterminate inflorescence meristems, coupled with iterative production of bract-like organs and higher order of inflorescences. A comparison of the LFY- and UFO-like genes (CbFLY and CbUFO) isolated from both the wild-type and gh cosmos revealed that CbUFO may play an important role in inflorescence differentiation into different structures and promotion of flower initiation, and the reduced expression of CbUFO in the gh cosmos could be associated with the phenotypes of the flower-defective plants. Further expression analysis indicated that CbUFO may promote the conversion of inflorescence meristem into floral meristem in early ray flower formation, but does not play a role in its later growth period.
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Duclos, Denise V. y Thomas Björkman. "Gibberellin Control of Reproductive Transitions in Brassica oleracea Curd Development". Journal of the American Society for Horticultural Science 140, n.º 1 (enero de 2015): 57–67. http://dx.doi.org/10.21273/jashs.140.1.57.
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Cauliflower (Brassica oleracea var. botrytis) and broccoli (B. oleracea var. italica) differ in the developmental stage of the reproductive meristem at harvest. A cauliflower head is formed by arrest at the inflorescence meristem stage and broccoli at the flower bud stage, and the horticultural value of the crop depends on synchronous development across the head. In other plant species, gibberellin (GA) can promote floral development and is therefore a candidate for providing the early developmental cues that shape the curd morphology. This research investigated the effect of GAs on the two horticulturally important transitions of the reproductive meristem: initiation of the inflorescence meristem and initiation of floral primordia on the proliferated inflorescence meristems. GA is known to affect the former in many species, but effects on the latter have not been determined. It is also not known whether one or both active forms produced by the two GA biosynthetic pathways is involved in the reproductive transitions in this crop. GAs from the early-13 hydroxylation pathway (GA3) and the non-13 hydroxylation pathway (GA4+7) were applied to the shoot apical meristems of cauliflower and broccoli at three developmental stages: adult-vegetative, curd initiation, and curd enlargement. GAs applied during the adult vegetative stage caused the curd to form faster and after fewer additional nodes in both cauliflower and broccoli. GAs applied to the inflorescence meristem did not cause floral primordia to form nor did the expression of transition-associated genes change. Integrator genes BoLFY and SOC1 had constant expression over 24 hours, and meristem-identity genes BoAP1-a and BoAP1-c remained undetectable. However, GAs applied early during the reproductive phase increased bract development in cauliflower curds. This study shows that GAs from both pathways can trigger the vegetative-to-reproductive transition in both cauliflower and broccoli, resulting in earlier curd formation. However, GAs did not advance the inflorescence-meristem-to-floral-primordium transition; on the contrary, they increased bract incidence in cauliflower, a sign of reversion toward the vegetative stage, suggesting that another pathway is responsible for this second transition in cauliflower and broccoli.
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Song, J. Y., T. Leung, L. K. Ehler, C. Wang y Z. Liu. "Regulation of meristem organization and cell division by TSO1, an Arabidopsis gene with cysteine-rich repeats". Development 127, n.º 10 (15 de mayo de 2000): 2207–17. http://dx.doi.org/10.1242/dev.127.10.2207.
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In higher plants, meristem organization and cell division regulation are two fundamentally important and intimately related biological processes. Identifying and isolating regulatory genes in these processes is essential for understanding higher plant growth and development. We describe the molecular isolation and analyses of an Arabidopsis gene, TSO1, which regulates both of these processes. We previously showed that tso1 mutants displayed defects in cell division of floral meristem cells including partially formed cell walls, increased DNA content, and multinucleated cells (Liu, Z., Running, M. P. and Meyerowitz, E. M. (1997). Development 124, 665–672). Here, we characterize a second defect of tso1 in influorescence meristem development and show that the enlarged influorescence in tso1 mutants results from repeated division of one inflorescence meristem into two or more influorescence meristems. Using a map-based approach, we isolated the TSO1 gene and found that TSO1 encodes a protein with cysteine-rich repeats bearing similarity to Drosophila Enhancer of zeste and its plant homologs. In situ TSO1 mRNA expression pattern and the nuclear localization of TSO1-GFP are consistent with a regulatory role of TSO1 in floral meristem cell division and in influorescence meristem organization.
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Sessions, Allen, Martin F. Yanofsky y Detlef Weigel. "Patterning the floral meristem". Seminars in Cell & Developmental Biology 9, n.º 2 (abril de 1998): 221–26. http://dx.doi.org/10.1006/scdb.1997.0206.
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Du, Yanfang, China Lunde, Yunfu Li, David Jackson, Sarah Hake y Zuxin Zhang. "Gene duplication at the Fascicled ear1 locus controls the fate of inflorescence meristem cells in maize". Proceedings of the National Academy of Sciences 118, n.º 7 (12 de febrero de 2021): e2019218118. http://dx.doi.org/10.1073/pnas.2019218118.
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Plant meristems are self-renewing groups of pluripotent stem cells that produce lateral organs in a stereotypical pattern. Of interest is how the radially symmetrical meristem produces laminar lateral organs. Both the male and female inflorescence meristems of the dominant Fascicled ear (Fas1) mutant fail to grow as a single point and instead show deep branching. Positional cloning of two independent Fas1 alleles identified an ∼160 kb region containing two floral genes, the MADS-box gene, zmm8, and the YABBY gene, drooping leaf2 (drl2). Both genes are duplicated within the Fas1 locus and spatiotemporally misexpressed in the mutant inflorescence meristems. Increased zmm8 expression alone does not affect inflorescence development; however, combined misexpression of zmm8, drl2, and their syntenic paralogs zmm14 and drl1, perturbs meristem organization. We hypothesize that misexpression of the floral genes in the inflorescence and their potential interaction cause ectopic activation of a laminar program, thereby disrupting signaling necessary for maintenance of radially symmetrical inflorescence meristems. Consistent with this hypothesis, RNA sequencing and in situ analysis reveal altered expression patterns of genes that define distinct zones of the meristem and developing leaf. Our findings highlight the importance of strict spatiotemporal patterns of expression for both zmm8 and drl2 and provide an example of phenotypes arising from tandem gene duplications.
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Bradley, D., C. Vincent, R. Carpenter y E. Coen. "Pathways for inflorescence and floral induction in Antirrhinum". Development 122, n.º 5 (1 de mayo de 1996): 1535–44. http://dx.doi.org/10.1242/dev.122.5.1535.
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The presentation of flowers on a modified stem, the inflorescence, requires the integration of several aspects of meristem behaviour. In Antirrhinum, the inflorescence can be distinguished by its flowers, hairy stem, modified leaves, short internodes and spiral phyllotaxy. We show, by a combination of physiological, genetical and morphological analysis, that the various aspects of the inflorescence are controlled by three pathways. The first pathway, depends on expression of the floricaula gene, and is rapidly and discretely induced by exposure to long daylength. Activation of this pathway occurs in very young axillary meristems, resulting in a floral identity. In addition, the length of subtending leaves and hairiness of the stem are partially modified. The second pathway affects leaf size, internode length, and stem hairiness, but does not confer floral meristem identity. This pathway is induced by long daylength, but not as rapidly or discretely as the floricaula-dependent pathway. The third pathway controls the switch in phyllotaxy from decussate to spiral and is activated independently of daylength. The coordination of these three programmes ensures that apical and axillary meristem behaviour is integrated.
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Pautler, Michael, Wakana Tanaka, Hiro-Yuki Hirano y David Jackson. "Grass Meristems I: Shoot Apical Meristem Maintenance, Axillary Meristem Determinacy and the Floral Transition". Plant and Cell Physiology 54, n.º 3 (14 de febrero de 2013): 302–12. http://dx.doi.org/10.1093/pcp/pct025.
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Immink, R. G., D. J. Hannapel, S. Ferrario, M. Busscher, J. Franken, M. M. Lookeren Campagne y G. C. Angenent. "A petunia MADS box gene involved in the transition from vegetative to reproductive development". Development 126, n.º 22 (15 de noviembre de 1999): 5117–26. http://dx.doi.org/10.1242/dev.126.22.5117.
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We have identified a novel petunia MADS box gene, PETUNIA FLOWERING GENE (PFG), which is involved in the transition from vegetative to reproductive development. PFG is expressed in the entire plant except stamens, roots and seedlings. Highest expression levels of PFG are found in vegetative and inflorescence meristems. Inhibition of PFG expression in transgenic plants, using a cosuppression strategy, resulted in a unique nonflowering phenotype. Homozygous pfg cosuppression plants are blocked in the formation of inflorescences and maintain vegetative growth. In these mutants, the expression of both PFG and the MADS box gene FLORAL BINDING PROTEIN26 (FBP26), the putative petunia homolog of SQUAMOSA from Antirrhinum, are down-regulated. In hemizygous pfg cosuppression plants initially a few flowers are formed, after which the meristem reverts to the vegetative phase. This reverted phenotype suggests that PFG, besides being required for floral transition, is also required to maintain the reproductive identity after this transition. The position of PFG in the hierarchy of genes controlling floral meristem development was investigated using a double mutant of the floral meristem identity mutant aberrant leaf and flower (alf) and the pfg cosuppression mutant. This analysis revealed that the pfg cosuppression phenotype is epistatic to the alf mutant phenotype, indicating that PFG acts early in the transition to flowering. These results suggest that the petunia MADS box gene, PFG, functions as an inflorescence meristem identity gene required for the transition of the vegetative shoot apex to the reproductive phase and the maintenance of reproductive identity.
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Chandler, J. W. y W. Werr. "A phylogenetically conserved APETALA2/ETHYLENE RESPONSE FACTOR, ERF12, regulates Arabidopsis floral development". Plant Molecular Biology 102, n.º 1-2 (5 de diciembre de 2019): 39–54. http://dx.doi.org/10.1007/s11103-019-00936-5.
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Abstract Key message Arabidopsis ETHYLENE RESPONSE FACTOR12 (ERF12), the rice MULTIFLORET SPIKELET1 orthologue pleiotropically affects meristem identity, floral phyllotaxy and organ initiation and is conserved among angiosperms. Abstract Reproductive development necessitates the coordinated regulation of meristem identity and maturation and lateral organ initiation via positive and negative regulators and network integrators. We have identified ETHYLENE RESPONSE FACTOR12 (ERF12) as the Arabidopsis orthologue of MULTIFLORET SPIKELET1 (MFS1) in rice. Loss of ERF12 function pleiotropically affects reproductive development, including defective floral phyllotaxy and increased floral organ merosity, especially supernumerary sepals, at incomplete penetrance in the first-formed flowers. Wildtype floral organ number in early formed flowers is labile, demonstrating that floral meristem maturation involves the stabilisation of positional information for organogenesis, as well as appropriate identity. A subset of erf12 phenotypes partly defines a narrow developmental time window, suggesting that ERF12 functions heterochronically to fine-tune stochastic variation in wild type floral number and similar to MFS1, promotes meristem identity. ERF12 expression encircles incipient floral primordia in the inflorescence meristem periphery and is strong throughout the floral meristem and intersepal regions. ERF12 is a putative transcriptional repressor and genetically opposes the function of its relatives DORNRÖSCHEN, DORNRÖSCHEN-LIKE and PUCHI and converges with the APETALA2 pathway. Phylogenetic analysis suggests that ERF12 is conserved among all eudicots and appeared in angiosperm evolution concomitant with the generation of floral diversity.
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Jiang, Xiaobing, Greice Lubini, José Hernandes-Lopes, Kim Rijnsburger, Vera Veltkamp, Ruud A. de Maagd, Gerco C. Angenent y Marian Bemer. "FRUITFULL-like genes regulate flowering time and inflorescence architecture in tomato". Plant Cell 34, n.º 3 (6 de diciembre de 2021): 1002–19. http://dx.doi.org/10.1093/plcell/koab298.
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Abstract The timing of flowering and the inflorescence architecture are critical for the reproductive success of tomato (Solanum lycopersicum), but the gene regulatory networks underlying these traits have not been fully explored. Here, we show that the tomato FRUITFULL-like (FUL-like) genes FUL2 and MADS-BOX PROTEIN 20 (MBP20) promote the vegetative-to-reproductive transition and repress inflorescence branching by inducing floral meristem (FM) maturation. FUL1 fulfils a less prominent role and appears to depend on FUL2 and MBP20 for its upregulation in the inflorescence- and floral meristems. MBP10, the fourth tomato FUL-like gene, has probably lost its function. The tomato FUL-like proteins cannot homodimerize in in vitro assays, but heterodimerize with various other MADS-domain proteins, potentially forming distinct complexes in the transition meristem and FM. Transcriptome analysis of the primary shoot meristems revealed various interesting downstream targets, including four repressors of cytokinin signaling that are upregulated during the floral transition in ful1 ful2 mbp10 mbp20 mutants. FUL2 and MBP20 can also bind in vitro to the upstream regions of these genes, thereby probably directly stimulating cell division in the meristem upon the transition to flowering. The control of inflorescence branching does not occur via the cytokinin oxidase/dehydrogenases (CKXs) but may be regulated by repression of transcription factors such as TOMATO MADS-box gene 3 (TM3) and APETALA 2b (AP2b).
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Sessions, A., J. L. Nemhauser, A. McColl, J. L. Roe, K. A. Feldmann y P. C. Zambryski. "ETTIN patterns the Arabidopsis floral meristem and reproductive organs". Development 124, n.º 22 (15 de noviembre de 1997): 4481–91. http://dx.doi.org/10.1242/dev.124.22.4481.
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ettin (ett) mutations have pleiotropic effects on Arabidopsis flower development, causing increases in perianth organ number, decreases in stamen number and anther formation, and apical-basal patterning defects in the gynoecium. The ETTIN gene was cloned and encodes a protein with homology to DNA binding proteins which bind to auxin response elements. ETT transcript is expressed throughout stage 1 floral meristems and subsequently resolves to a complex pattern within petal, stamen and carpel primordia. The data suggest that ETT functions to impart regional identity in floral meristems that affects perianth organ number spacing, stamen formation, and regional differentiation in stamens and the gynoecium. During stage 5, ETT expression appears in a ring at the top of the floral meristem before morphological appearance of the gynoecium, consistent with the proposal that ETT is involved in prepatterning apical and basal boundaries in the gynoecium primordium. Double mutant analyses and expression studies show that although ETT transcriptional activation occurs independently of the meristem and organ identity genes LEAFY, APETELA1, APETELA2 and AGAMOUS, the functioning of these genes is necessary for ETT activity. Double mutant analyses also demonstrate that ETT functions independently of the ‘b’ class genes APETELA3 and PISTILLATA. Lastly, double mutant analyses suggest that ETT control of floral organ number acts independently of CLAVATA loci and redundantly with PERIANTHIA.
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Bolivar-Medina, Jenny L., Camilo Villouta, Beth Ann Workmaster y Amaya Atucha. "Floral Meristem Development in Cranberry Apical Buds during Winter Rest and Its Implication on Yield Prediction". Journal of the American Society for Horticultural Science 144, n.º 5 (septiembre de 2019): 314–20. http://dx.doi.org/10.21273/jashs04691-19.
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The formation and development of floral meristems is key to fruit production. However, limited information regarding the development of floral buds during the dormant period of cranberry (Vaccinium macrocarpon) constrains the ability to forecast yield early and accurately. The objectives of this study were to characterize the development of floral meristems from fall to spring and to evaluate the number of floral meristems formed across different bud sizes and upright types, as well as their contribution to the fruit production of the next year. Apical buds of different sizes on vegetative and fruiting uprights were tagged and collected periodically from fall to spring for histological study. An extra set of tagged buds was left in the field to evaluate their flower and fruit production. Five stages of floral development were identified based on the concentric differentiation of organ primordia. Large buds from vegetative uprights developed earlier, had a higher number of floral meristems, and became fruiting uprights; they had the highest number of flowers and fruit. Buds from fruiting uprights had the lowest number of floral meristems and delayed development; subsequently, they had the lowest number of fruit per upright. Our results provide evidence of active floral meristem differentiation during fall and winter, as well as differences in the timing and development stage according to bud size. In addition, our study shows that upright types and bud sizes influence the fruit production of the following year; therefore, they should be considered in cranberry crop forecasting models.
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Esumi, Tomoya, Ryutaro Tao y Keizo Yonemori. "(280) Temporal and Spatial Expression of LEAFY and TERMINAL FLOWER 1 Homologues in Floral Bud of Japanese Pear and Quince". HortScience 41, n.º 4 (julio de 2006): 1052B—1052. http://dx.doi.org/10.21273/hortsci.41.4.1052b.
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Japanese pear (Pyrus pyrifolia) and quince (Cydonia oblonga), both classified in the subfamily Maloideae, show differences in inflorescence architectures despite of the fact that they are genetically closely related. We previously isolated flowering related genes, LEAFY (LFY) and TERMINAL FLOWER 1 (TFL1) homologues, from these species and showed that they had two types of homologues for each gene. In this study, we examined the expression pattern of LFY and TFL1 homologues in these species by in situ hybridization and RT-PCR. The floral bud was dissected to small pieces under stereomicroscope; apical meristem, scales/bracts, pith, floral meristem, and inflorescence; and then used for RT-PCR. The LFY homologues were expressed in apical meristem and scales/bracts before the floral differentiation in both Japanese pear and quince. After floral differentiation, the expression was observed in floral meristem, scales/bracts and pith in both the species. The TFL1 homologues were strongly expressed in the apical meristem, but their expression was drastically decreased just before floral differentiation. It is considered that the decrease of expression of TFL1 homologues is a sign of floral initiation. The expression of TFL1 homologues was transiently increased at the beginning of floral differentiation in both species. Moreover, one of TFL1 homologues in Japanese pear was continuously expressed in the inflorescence part in the floral primordia, whereas expression of TFL1 homologues in quince almost completely disappeared after a solitary floral meristem was initiated. It was suggested that TFL1 homologues may also be involved in the inflorescence development of Japanese pear.
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Laufs, P., J. Dockx, J. Kronenberger y J. Traas. "MGOUN1 and MGOUN2: two genes required for primordium initiation at the shoot apical and floral meristems in Arabidopsis thaliana". Development 125, n.º 7 (1 de abril de 1998): 1253–60. http://dx.doi.org/10.1242/dev.125.7.1253.
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We report two new recessive mutations in Arabidopsis, mgoun1 and mgoun2 which cause a reduction in the number of leaves and floral organs, larger meristems and fasciation of the inflorescence stem. Although meristem structure is affected in the mutants, we provide evidence that its overall organisation is normal, as shown by the expression patterns of two meristem markers. Microscopical analyses suggest that both mutations affect organ primordia production. mgo1 strongly inhibits leaf production in a weak allele of shoot meristemless, stm-2. In addition, mgo1 and 2 severely reduce the ability of the fasciata1 and 2 mutants to initiate organs, although meristem formation per se was not inhibited. The strong allele, stm-5, is epistatic to mgo1, showing that the presence of meristematic cells is essential for MGO1 function. These results suggest a role for the MGO genes in primordia initiation although a more general role in meristem function can not be excluded. We describe a form of fasciation which is radically different from that described for clavata, which is thought to have an increased size of the meristem centre. Instead of one enlarged central meristem mgo1 and 2 show a continuous fragmentation of the shoot apex into multiple meristems, which leads to the formation of many extra branches. The phenotype of mgo1 clv3 and mgo2 clv3 double mutants suggest that the MGO and CLV genes are involved in different events. In conclusion, our results reveal two new components of the regulatory network controlling meristem function and primordia formation. A model for MGO genes is discussed.
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Irish, E. E. y T. M. Nelson. "Identification of multiple stages in the conversion of vegetative to floral development". Development 112, n.º 3 (1 de julio de 1991): 891–98. http://dx.doi.org/10.1242/dev.112.3.891.
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Vegetative growth in most lines of maize is terminated stage in development by the conversion of the shoot inflorescence, the tassel. The conversion from under developmental control, the basis of which is developmental potential of the shoot apical meristem stage at which it is determined to form a tassel. We culture, that meristems are not determined to form a vegetative nodes have been initiated. We also show separate, later event in the development of a maize stages can be distinguished in which the meristem is phyllotaxis of a tassel when cultured but develops that normally give rise to sets of florets.
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Fletcher, Jennifer. "The CLV-WUS Stem Cell Signaling Pathway: A Roadmap to Crop Yield Optimization". Plants 7, n.º 4 (19 de octubre de 2018): 87. http://dx.doi.org/10.3390/plants7040087.
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The shoot apical meristem at the growing shoot tip acts a stem cell reservoir that provides cells to generate the entire above-ground architecture of higher plants. Many agronomic plant yield traits such as tiller number, flower number, fruit number, and kernel row number are therefore defined by the activity of the shoot apical meristem and its derivatives, the floral meristems. Studies in the model plant Arabidopsis thaliana demonstrated that a molecular negative feedback loop called the CLAVATA (CLV)-WUSCHEL (WUS) pathway regulates stem cell maintenance in shoot and floral meristems. CLV-WUS pathway components are associated with quantitative trait loci (QTL) for yield traits in crop plants such as oilseed, tomato, rice, and maize, and may have played a role in crop domestication. The conservation of these pathway components across the plant kingdom provides an opportunity to use cutting edge techniques such as genome editing to enhance yield traits in a wide variety of agricultural plant species.
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ÇETİNBAŞ, Aslıhan y Meral ÜNAL. "Comparative Ontogeny of Hermaphrodite and Pistillate Florets in Helianthus annuus L. (Asteraceae)". Notulae Scientia Biologicae 4, n.º 2 (10 de mayo de 2012): 30–40. http://dx.doi.org/10.15835/nsb427576.
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The inflorescence of Helianthus annuus L. has two types of flowers (or florets) on a single capitulum; central hermaphrodite disc florets and peripheral pistillate ray florets. In both florets, reproductive development starts with the conversion of apical meristem into floral meristem that will produce floral organ primordia. The only difference between hermaphrodite and pistillate florets in apical meristem stage is that apical meristem of the pistillate florets is not as apparent and curvaceous as apical meristem of the hermaphrodite florets. The differentiation of apical meristem into floral meristem is in the same progress in both florets. In hermaphrodite florets, flower organs; petals, stamens and carpels develop from floral meristem. Differentiation of five petal primordia takes place in the same way in both florets. Firstly filament and then anther differentiates in a stamen. Two carpel primordia appear below the stamen primordia in hermaphrodite florets. In following stages, carpel primordia are lengthened and formed inferior ovary, style, stigma respectively. In pistillate florets, flower organs; petals and carpels develop from floral meristem. They pass directly from the periant initiation to the start of carpel formation. Stamen primordia don’t appear and the further development of carpel primordia stops in a short time, as a result, stigma and style do not exist in pistillate florets. However, an inferior ovary with no ovule forms. In the capitulum of hermaphrodite florets, the development takes place in a centripetal manner; it starts firstly on the outermost whorl, and it proceeds towards inner whorl. However, this is not the case in pistillate florets.
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Hong, Linh Tran Minh, Tu Cam Trinh, Viet Trang Bui y Huong Thanh Tran. "Roles of plant growth regulators on flowering of rose (Rosa hybrida L.’Red Rose’)". IOP Conference Series: Earth and Environmental Science 947, n.º 1 (1 de diciembre de 2021): 012039. http://dx.doi.org/10.1088/1755-1315/947/1/012039.
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Abstract Rose is the most popular ornamental flower all over the world, which is used as garden plants and cut flowers. In the case of Rosa hybrida L. ’Red Rose’, flowering provides the major developmental transition from the vegetative to the reproductive stage, and reproduction is one of the most important phases in an organism’s life cycle. In this study, the morphological and physiological changes during the flower development of rose, which is planted in the garden, and roles of plant growth regulators on the flowering of in vitro vegetative shoots of rose were analyzed. The development of a flower includes three stages: the shoot apical meristem, floral meristem, floral bud. Levels of cytokinin, auxins, and gibberellins increased in the transition of meristem from the shoot apical meristem to the floral meristem stage. Plant growth regulators have important effects on the shoot apical meristem cell division and flowering. The combination of 0.5 mg.L−1 GA3, 0.1 mg.L−1 NAA, 2.5 or 3.0 mg.L−1 BA to Murashige and Skoog (MS) medium induces the floral transition of the in vitro vegetative shoots with the highest percentage (41%) as well as growth and development in comparison to the other treatments after 10 weeks. Then, the in vitro floral meristem continuously developed into a flower bud after 12 weeks.
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Kerstetter, R. A., D. Laudencia-Chingcuanco, L. G. Smith y S. Hake. "Loss-of-function mutations in the maize homeobox gene, knotted1, are defective in shoot meristem maintenance". Development 124, n.º 16 (15 de agosto de 1997): 3045–54. http://dx.doi.org/10.1242/dev.124.16.3045.
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The product of the maize homeobox gene, knotted1 (kn1), localizes to the nuclei of cells in shoot meristems, but is absent from portions of the meristem where leaf primordia or floral organs initiate. Recessive mutant alleles of kn1 were obtained by screening for loss of the dominant leaf phenotype in maize. Mutant kn1 alleles carrying nonsense, splicing and frame shift mutations cause severe inflorescence and floral defects. Mutant tassels produce fewer branches and spikelets. Ears are often absent, and when present, are small with few spikelets. In addition, extra carpels form in female florets and ovule tissue proliferates abnormally. Less frequently, extra leaves form in the axils of vegetative leaves. These mutations reveal a role for kn1 in meristem maintenance, particularly as it affects branching and lateral organ formation.
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Sun, Bo y Toshiro Ito. "Floral stem cells: from dynamic balance towards termination". Biochemical Society Transactions 38, n.º 2 (22 de marzo de 2010): 613–16. http://dx.doi.org/10.1042/bst0380613.
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During early flower development in Arabidopsis, floral stem cells proliferate and produce a sufficient amount of cells that are recruited for organogenesis. However, after the central organ primordia initiate, stem cell activity in the floral meristem is terminated to ensure the differentiation of a fixed number of floral organs. Underlying this process, the genetic programme regulating the fate of floral meristems undergoes a shift from a spatially balanced signalling scheme for stem cell maintenance to a temporally controlled transcriptional scheme for stem cell termination. Precise timing of stem cell termination is a key issue for flower development, which is secured by the orchestration of multiple regulators in transcriptional and epigenetic regulation.
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Weigel, D. y S. E. Clark. "Sizing Up the Floral Meristem". Plant Physiology 112, n.º 1 (1 de septiembre de 1996): 5–10. http://dx.doi.org/10.1104/pp.112.1.5.
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Bertoni, Gregory. "PUCHI and Floral Meristem Identity". Plant Cell 21, n.º 5 (mayo de 2009): 1327. http://dx.doi.org/10.1105/tpc.109.210512.
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Talbert, P. B., H. T. Adler, D. W. Parks y L. Comai. "The REVOLUTA gene is necessary for apical meristem development and for limiting cell divisions in the leaves and stems of Arabidopsis thaliana". Development 121, n.º 9 (1 de septiembre de 1995): 2723–35. http://dx.doi.org/10.1242/dev.121.9.2723.
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The form of seed plants is determined by the growth of a number of meristems including apical meristems, leaf meristems and cambium layers. We investigated five recessive mutant alleles of a gene REVOLUTA that is required to promote the growth of apical meristems and to limit cell division in leaves and stems of Arabidopsis thaliana. REVOLUTA maps to the bottom of the fifth chromosome. Apical meristems of both paraclades (axillary shoots) and flowers of revoluta mutants frequently fail to complete normal development and form incomplete or abortive structures. The primary shoot apical meristem sometimes also arrests development early. Leaves, stems and floral organs, in contrast, grow abnormally large. We show that in the leaf epidermis this extra growth is due to extra cell divisions in the leaf basal meristem. The extent of leaf growth is negatively correlated with the development of a paraclade in the leaf axil. The thickened stems contain extra cell layers, arranged in rings, indicating that they may result from a cambium-like meristem. These results suggest that the REVOLUTA gene has a role in regulating the relative growth of apical and non-apical meristems in Arabidopsis.
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Yu, L. P., E. J. Simon, A. E. Trotochaud y S. E. Clark. "POLTERGEIST functions to regulate meristem development downstream of the CLAVATA loci". Development 127, n.º 8 (15 de abril de 2000): 1661–70. http://dx.doi.org/10.1242/dev.127.8.1661.
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Mutations at the CLAVATA loci (CLV1, CLV2 and CLV3) result in the accumulation of undifferentiated cells at the shoot and floral meristems. We have isolated three mutant alleles of a novel locus, POLTERGEIST (POL), as suppressors of clv1, clv2 and clv3 phenotypes. All pol mutants were nearly indistinguishable from wild-type plants; however, pol mutations provided recessive, partial suppression of meristem defects in strong clv1 and clv3 mutants, and nearly complete suppression of weak clv1 mutants. pol mutations partially suppressed clv2 floral and pedicel defects in a dominant fashion, and almost completely suppressed clv2 phenotypes in a recessive manner. These observations, along with dominant interactions observed between the pol and wuschel (wus) mutations, indicate that POL functions as a critical regulator of meristem development downstream of the CLV loci and redundantly with WUS. Consistent with this, pol mutations do not suppress clv3 phenotypes by altering CLV1 receptor activation.
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Running, M. P. y E. M. Meyerowitz. "Mutations in the PERIANTHIA gene of Arabidopsis specifically alter floral organ number and initiation pattern". Development 122, n.º 4 (1 de abril de 1996): 1261–69. http://dx.doi.org/10.1242/dev.122.4.1261.
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An open question in developmental biology is how groups of dividing cells can generate specific numbers of segments or organs. We describe the phenotypic effects of mutations in PERIANTHIA, a gene specifically required for floral organ patterning in Arabidopsis thaliana. Most wild-type Arabidopsis flowers have 4 sepals, 4 petals, 6 stamens, and 2 carpels. Flowers of perianthia mutant plants most commonly show a pentamerous pattern of 5 sepals, 5 petals 5 stamens, and 2 carpels. This pattern is characteristic of flowers in a number of plant families, but not in the family Brassicaceae, which includes Arabidopsis. Unlike previously described mutations affecting floral organ number, perianthia does not appear to affect apical or floral meristem sizes, nor is any other aspect of vegetative or floral development severely affected. Floral organs in perianthia arise in a regular, stereotypical pattern similar to that in distantly related species with pentamerous flowers. Genetic analysis shows that PERIANTHIA acts downstream of the floral meristem identity genes and independently of the floral meristem size and floral organ identity genes in establishing floral organ initiation patterns. Thus PERIANTHIA acts in a previously unidentified process required for organ patterning in Arabidopsis flowers.