Academic literature on the topic 'PRR Signaling'

L’activation des réponses immunitaires des plantes repose sur la reconnaissance de motifs moléculaires associés aux pathogènes (aussi appelés PAMP) par des récepteurs de l’immunité, également nommés PRR (pattern recognition receptors). La chitine, principal composant de la paroi des champignons, est un PAMP bien caractérisé qui induit des réponses de défense aussi bien chez les mammifères que chez les plantes.La première partie de cette étude met en évidence que deux chito-oligosaccharides, la chitine et le chitosan, agissent comme des PAMP chez la vigne (Vitis vinifera) puisqu’ils induisent des évènements précoces de signalisation, l’expression de gènes de défense et une résistance contre des agents pathogènes. Ces résultats suggèrent que des systèmes de perception existent chez la vigne. Une analyse phylogénétique a permis d’identifier trois récepteurs kinases à domaine LysM (LysM-RK ou LYK) chez V. vinifera (VvLYK1-1, -2, -3) appartenant au même clade que le récepteur à la chitine chez Arabidopsis et nommé AtCERK1 (Arabidopsis thaliana Chitin Elicitor Receptor Kinase 1). Leur analyse fonctionnelle a été réalisée par complémentation du mutant d’Arabidopsis Atcerk1, affecté dans la perception de la chitine. Nos résultats montrent que VvLYK1-1 et VvLYK1-2, mais pas VvLYK1-3, complémentent fonctionnellement le mutant Atcerk1 en restaurant l’activation des MAPK (Mitogen-Activated Protein Kinases) et l’expression de gènes de défense induits par les chito-oligosaccharides. De plus, l’expression de VvLYK1-1 chez Atcerk1 restaure la résistance basale à l’agent de l’oïdium de la vigne (Erysiphe necator).La seconde partie du projet s’est focalisée sur les éliciteurs oligosaccharidiques de type « damage-associated molecular patterns (DAMP) ». Ces molécules endogènes peuvent provenir de la dégradation de la paroi lors d’une attaque et sont capables d’activer les réponses immunitaires de la plante. Les DAMP les mieux caractérisés actuellement sont les oligogalacturonates (OG), des fragments de pectine qui induisent des réponses immunitaires chez de nombreuses espèces végétales dont l’activation de MAPK, la production d’H2O2, l’expression de gènes de défense et le dépôt de callose. Nous avons montré dans cette étude que les xyloglucanes (Xh), des fragments d’hémicellulose pariétale purifiés, induisaient l’activation de MAPK et l’expression de gènes de défense chez la vigne et Arabidopsis, afin d’induire une résistance contre le champignon nécrotrophe Botrytis cinerea. Les Xh induisent également la production de resvératrol, une phytoalexine majoritaire chez la vigne, et un dépôt de callose chez Arabidopsis. Par une approche génétique, nous avons identifié certains composants de la signalisation induite par les Xh chez Arabidopsis. L’utilisation de mutants suggère que la résistance induite par les Xh contre B. cinerea est dépendante des voies de la camalexine, de l’acide salicylique, de l’acide jasmonique et de l’éthylène chez Arabidopsis. De manière globale, nos résultats mettent en lumière que les xyloglucanes peuvent être considérés comme de nouveaux éliciteurs de l’immunité chez la vigne et Arabidopsis<br>Activation of the plant immune responses requires recognition of common pathogen-associated molecular pattern (PAMP) by their cognate pattern recognition receptors (PRR). Chitin, a major component of fungal cell walls, is a well-known PAMP that triggers defense responses in several mammal and plant species.In the first part of this study, we show that two chitooligosaccharides, chitin and chitosan, act as PAMPs in grapevine (Vitis vinifera) as they elicit immune signaling events, defense gene expression, and resistance against pathogens. These two PAMPs are active in grapevine suggesting that at least one perception system exists. Phylogenetic analysis clearly distinguished three V. vinifera LysM Receptor Kinases (VvLYK1-1, -2, -3) located in the same clade as the Arabidopsis Chitin Elicitor Receptor Kinase 1 (AtCERK1), which mediates chitin-induced immune responses. Their functional characterization was achieved by complementation assays in the Atcerk1 mutant, impaired in chitin perception. Our results provide evidence that VvLYK1-1 and VvLYK1-2, but not VvLYK1-3, functionally complement the loss of AtCERK1 function by restoring chitooligosaccharide-induced MAPK activation and immune gene expression. Moreover, expression of VvLYK1-1 in Atcerk1 restored penetration resistance to the non-adapted grapevine powdery mildew (Erysiphe necator).The second part of this study focused on damaged-associated molecular patterns (DAMP), endogenous molecules that can be released from the plant cell wall during an attack and activate the plant innate immunity. Until now, the best characterized DAMPs are oligogalacturonides (OG) coming from pectin fragments that induce innate immune responses in various plant species, including MAPK activation, H2O2 production, defense gene expression and callose deposition. In this study, we showed that purified xyloglucans (Xh), derived from the plant cell wall hemicellulose, elicit MAPK activation and immune gene expression in grapevine (V. vinifera) and Arabidopsis to trigger induced resistance against the necrotrophic fungus Botrytis cinerea. Xh also elicit the production of resveratrol, the main grapevine phytoalexin, and callose deposition in Arabidopsis. Using a genetic approach, we identified some signaling components of Xh-induced immunity. The use of Arabidopsis mutants suggests that Xh-induced resistance against B. cinerea is dependent on the camalexin, salicylate, jasmonate and ethylene pathways. Taken together, our data highlight that Xh can be considered as new elicitors of grapevine and Arabidopsis immunity

This work has shown that 11βHSD-1 mRNA is present at highest levels in the menstrual phase of the cycle and in first trimester deciduas, the times when an inflammatory response is evident. 11βHSD-2 mRNA and protein are present at all stages of the cycle, and also in first trimester deciduas. GR mRNA and protein are highly expressed throughout the cycle. MR mRNA expression varies across the cycle in a pattern similar to progesterone expression. 11βHSD-1 mRNA expression is increased in response to IL-1α and cortisol, and GR mRNA shows a similar trend. 11βHSD-1 and MR expression are not altered by IL-1α or cortisol.3βHSD-1 mRNA has been shown to be present only in first trimester deciduas; 3βHSD-1 is not detectable by these methods. Immunohistochemistry using an antibody which detects both 3βHSD-1 and -2 has shown low levels of protein in the tissues studied. AKR1C1-3 mRNAs are expressed throughout the menstrual cycle; all three enzymes are predominantly expressed in the secretory phase. AKR1C3 is localised to the glandular and surface epithelial cells, and vascular endothelium. AKR1C4 mRNA is not detectable in the endometrium at any stage of the menstrual cycle. Expression of steroid-metabolising enzymes is perturbed in the endometrium of users of a Levonorgestrel intra-uterine system, and also the following GnRH antagonist treatment for sub-fertility. These studies have shown that the endometrium has the ability to precisely regulate its balance of steroid hormone availability at a local level, and that this balance may be altered following administration of exogenous steroids. Further functional studies such as knockout or knockdown of these enzymes would expand this knowledge and fully elucidate steroid hormone metabolism and pre-receptor signalling.

The study of cell signalling in schistosomes is crucial in deepening our knowledge of the biology of these blood flukes, which affect hundreds of millions of people worldwide. Here, Akt/protein kinase B (PKB) signalling has been functionally characterised and mapped in Schistosoma mansoni; an Akt variant of approximately 52 kDa has been characterised and RNA interference of the S. mansoni Akt gene, resulted in an 84% reduction in Akt expression. The phosphorylation (activation) status of the characterised Akt protein was increased by host molecules, including insulin and L-arginine in somules and adult worms, and L-arginine and linoleic acid in cercariae. Akt phosphorylation (activation) was also attenuated by Akt Inhibitor X and herbimycin A treatment. Immunohistochemistry/confocal laser scanning microscopy revealed phosphorylated Akt in all S. mansoni human infective/resident life stages. Somules and adult worms displayed activated Akt primarily in the tegument, particularly the tubercles and gynaecophoric canal of adult males. Cercariae exhibited activated Akt in the nervous system and punctate regions along the length of the tail prompting investigation into the role of Akt in cercarial motility. Behavioural studies demonstrated a significant increase in cercarial swimming in response to host factors, which was attenuated following exposure to Akt inhibitor X. The striking activation of Akt observed in the tegument of adult worms stimulated research into its possible role in glucose uptake in this host-interactive layer. RNAi of Akt resulted in a 59% and 47% reduction in SGTP4 glucose transporter expression in male and female adult worms respectively with a concomitant reduction in glucose uptake by the parasite. In somules, the expression of SGTP4 and its evolution at the apical tegument membrane during transformation were significantly attenuated by Akt Inhibitor X; a 74% reduction in glucose uptake was also demonstrated following Akt inhibition. Bioinformatic analysis of S. mansoni Akt interacting proteins uncovered a putative connection between Akt and Rab vesicle trafficking proteins and a mechanistic model illuminating the possible role of Akt in the translocation of SGTP4 to the parasite surface was proposed. Collectively, this research highlights the significance of Akt in schistosome homeostasis and host-parasite interactions and thus demonstrates that Akt may be a suitable target for anti-schistosome drug development strategies.

Biochemistry<br>Ph.D.<br>Retinoic acid receptor (RAR), a member of the steroid/thyroid hormone nuclear receptor superfamily, functions as a RA-dependent transcription activator bound to the RA response element (RARE) within the promoter or enhancer region of target genes. The transcriptional activity of RAR is modulated by a large number of coregulators including coactivators and corepressors. Acinus is a nuclear protein with three isoforms (Acinus-L, Acinus-S and Acinus-S'). Acinus-S' interacts with the A/B domain of RAR and represses RAR-regulated genes expression. Acinus (without isoform definition) has been identified as a component of nuclear speckles, the spliceosome and the exon junction complex (EJC), suggesting its localization in nuclear speckles and involvement in RNA processing. Acinus-S has been shown to localize in nuclear speckles. However, it is unclear whether the other two isoforms also localize in nuclear speckles. In addition, the role of Acinus in regulating pre-mRNA splicing is unclear. The goal of these studies was to examine the nuclear localization of Acinus-L and Acinus-S' and to determine the role of Acinus isoforms in RAR-dependent splicing. The sub-nuclear localization of Acinus-L and Acinus-S' was determined using fluorescence microscopy. Acinus-S' colocalizes with SC35 in nuclear speckles while Acinus-L localizes diffusely throughout the nucleoplasm. RA treatment has little effect on the sub-nuclear localization of Acinus-L and Acinus-S'. The domains/regions necessary for the distinct sub-nuclear localization of Acinus-L and Acinus-S' were identified. The speckled sub-nuclear localization of Acinus-S' is dependent on its C-terminal RS- and RD/E-rich region but is independent of the phosphorylation status of Ser-453 and Ser-604 within this region. The unique N-terminal SAP-motif of Acinus-L is responsible for its diffuse localization in the nucleus. Moreover, the sub-nuclear localization of Acinus isoforms is affected by each other, which is determined by the combinatorial effect of the more potent SAP motif of Acinus-L and the C-terminal RS- and RD/E-rich region in all Acinus isoforms. The C-terminal RS- and RD/E-rich region of Acinus mediates the colocalization of Acinus isoforms as well as with its interacting protein RNPS1. The role of Acinus isoforms in regulating pre-mRNA splicing was explored using in vivo splicing assays. Both Acinus-L and Acinus-S', with the activity of Acinus-L higher than that of Acinus-S', increase the splicing of a RA-responsive minigene containing a weak 5' splice site but not a RA-responsive minigene containing a strong 5' splice site. RA treatment further enhances the splicing activity of Acinus in a dose- and time-dependent manner, suggesting a RA-dependent activity in addition to a RA-independent activity of Acinus. The RA-independent effect of Acinus on the splicing of pre-mRNAs containing the weak 5' splice site occurs to varying degrees using minigene constructs containing several different promoters while the RA-dependent splicing activity of Acinus is specific for transcripts derived from the minigene driven by the RARE-containing promoter. This suggests that the ligand-dependent splicing activity of Acinus is related to the RA-activated RAR bound to the RARE. The ligand-dependent splicing activity of Acinus was further shown to be promoter-specific, depending on the ligand-dependent transcription activator. The RRM domain was identified to be necessary for the RA-dependent splicing activity of Acinus. The RA-independent splicing activity of Acinus is repressed by RNPS1. Unexpectedly, the C-terminal RS- and RD/E rich region is dispensable for the splicing activity of Acinus in regulating the minigene containing a weak 5' splice site. Importantly, measurement of the splicing of endogenous human RARâ and Bcl-x in vivo demonstrates that Acinus stimulates the use of the weaker alternative 5' splice site of these two genes in a RA-dependent manner for RARâ and in a RA-independent manner for Bcl-x. Taken together, these studies demonstrate the distinct sub-nuclear localization of Acinus-L and Acinus-S', and identified the domains that are responsible for their sub-nuclear localization, which shed light on possible distinct functions between Acinus isoforms. In addition, both Acinus-L and Acinus-S' have been shown to be splicing cofactors (with the activity of Acinus-L higher than that of Acinus-S') that facilitate constitutive splicing of pre-mRNAs containing a weak 5' splice site and regulate alternative splicing in favor of the isoform generated from the weaker alternative 5' splice site. Both Acinus-L and Acinus-S' have a RA-dependent splicing activity specific for RA-responsive genes, which suggests that Acinus functions in RAR-dependent splicing.<br>Temple University--Theses

Communication between neuronal and non-neuronal is called volume transmission when the released neurotransmitter (NT) acts via diffusion and affects several target cells. Both the neurosecretory and postsynaptic cell responses are linked to [Ca2+]i elevations. In the present thesis the role of pre-and postsynaptic Ca2+ elevations has been investigated in the reconstituted "synapse" model comprised of NGF-differentiated PC12 and HEL cells as well as in SH-SY5Y neuroblastoma cells. In PC12 cells, both 70mM K+ and nicotine triggered NT release, which could be detected as a secondary [Ca2+]i increase in surrounding HEL cells. Both secretagogues shared the same voltage-dependent Ca2+ influx pathway as judged from the pharmacological profile blockers of voltage-gated Ca2+ channels. The coupling of electrical responses to the activation of Ca2+ signaling via muscarinic receptors in SH-SY5Y cells was also studied. These data revealed that depolarization caused a considerable potentiation of the muscarinic Ca2+ response. The potentiated Ca2+ increase was mainly dependent on the enhanced Ca2+ influx and to a lesser extent on [Ca2+]i release from intracellular stores. A phospholipase C (PLC) activator, m-3M3FBS was used to further study the role of G-protein coupled receptor (GPCR)-coupled Ca2+ signaling. However, it was found that m-3M3FBS instead triggered [Ca2+]i elevations independently of PLC activation. In conclusion, the results indicate that the magnitude of NT release from PC12 cells is sufficient to cause a robust activation of neighboring target cells. Postsynaptic muscarinic signaling is amplified due to integration of electrical excitation and GPCR signaling. The PLC activator, m-3M3FBS is not suitable for studies of PLC-mediated signals in intact cells.

La llum és un dels senyals ambientals més importants que influeixen en el cicle de vida de la planta. Les plantes han desenvolupat un conjunt de complexos mecanismes moleculars que detecten canvis en la qualitat i quantitat de la llum. Els PHYTOCHROME INTERACTING FACTORS (PIFs) són factors de transcripció que interactuen amb els fotoreceptors fitocroms (phy) i intervenen les respostes a llum vermella / vermella llunyana. Els PIF estan involucrats en la regulació d'una àmplia gamma de processos de desenvolupament. S'han estudiat àmpliament en Arabidopsis thaliana, però se sap molt poc sobre el seu paper en altres espècies. En aquesta tesi, vam investigar el paper dels dos homòlegs de PIF1 presents en tomàquet (Solanum lycopersicum): PIF1a i PIF1b. L'anàlisi de l'expressió de PIF1a i PIF1b va mostrar patrons molt diferents, el que indica una possible divergència evolutiva en els seus rols. Els experiments d'estabilitat de les corresponents proteïnes en llum vermella i vermella llunyana van revelar que PIF1b ha perdut la seva capacitat d'interactuar amb PhyB, mentre que PIF1a encara pot fer-ho, confirmant la hipòtesi de divergència evolutiva. D'altra banda, l'edició del genoma de plantes de tomàquet per CRISPR-CAS9 va generar línies de pèrdua de funció pif1a i pif1b, així com mutants dobles pif1a pif1b. La caracterització fenotípica d'aquests mutants va mostrar que tots dos factors de transcripció estan involucrats en la regulació de la germinació de les llavors, la síntesi de pigments en les fulles durant la des-etiolació i la producció de fruits. Altres processos estan regulats només per PIF1a, com l'allargament de pèls radiculars, la síntesi de glicoalcaloides esteroides en fulles, el temps de floració i el creixement i estovament del fruit. No identifiquem cap procés que estigui regulat específicament per PIF1b. A causa del paper central de PIF1a, vam decidir realitzar experiments de RNA-seq en línies induïbles. Els resultats van mostrar que la inducció de PIF1a té un impacte relativament menor en el perfil transcriptòmic, i que els possibles gens diana de PIF1a en tomàquet són diferents dels identificats prèviament en Arabidopsis. Totes aquestes dades en conjunt suggereixen que PIF1a i, en molt menor grau, PIF1b comparteixen algunes funcions amb el seu homòleg PIF1 d'Arabidopsis, però també il·lustren que s'han produït esdeveniments de neofuncionalització en tomàquet. Al fer això, l'evolució ha pogut utilitzar el potencial d'aquests factors de transcripció per regular nous processos específics en aquest cultiu d'interès agronòmic.<br>La luz es una de las señales ambientales más importantes que influyen en el ciclo de vida de la planta. Las plantas han desarrollado un conjunto de complejos mecanismos moleculares que detectan cambios en la calidad y cantidad de la luz. Los PHYTOCHROME INTERACTING FACTORs (PIFs) son factores de transcripción que interactúan con los fotorreceptores fitocromos (phy) y median las respuestas a luz roja/roja lejana. Los PIF están involucrados en la regulación de una amplia gama de procesos del desarrollo. Se han estudiado ampliamente en Arabidopsis thaliana, pero se sabe muy poco sobre su papel en otras especies. En esta tesis, investigamos el papel de los dos homólogos de PIF1 presentes en tomate (Solanum lycopersicum): PIF1a y PIF1b. El análisis de la expresión de PIF1a y PIF1b mostró patrones muy diferentes, lo que indica una posible divergencia evolutiva en sus roles. Los experimentos de estabilidad de las correspondientes proteínas en luz roja y roja lejana revelaron que PIF1b ha perdido su capacidad de interactuar con PhyB, mientras que PIF1a todavía puede hacerlo, confirmando la hipótesis de divergencia evolutiva. Por otro lado, la edición del genoma de plantas de tomate por CRISPR-Cas9 generó líneas de pérdida de función pif1a y pif1b, así como mutantes dobles pif1a pif1b. La caracterización fenotípica de estos mutantes mostró que ambos factores de transcripción están involucrados en la regulación de la germinación de las semillas, la síntesis de pigmentos en las hojas durante la des-etiolación y la producción de frutos. Otros procesos están regulados solo por PIF1a, como el alargamiento de pelos radiculares, la síntesis de glicoalcaloides esteroideos en hojas, el tiempo de floración y el crecimiento y ablandamiento del fruto. No identificamos ningún proceso que esté regulado específicamente por PIF1b. Debido al papel central de PIF1a, decidimos realizar experimentos de RNA-seq en líneas inducibles. Los resultados mostraron que la inducción de PIF1a tiene un impacto relativamente menor en el perfil transcriptómico, y que los posibles genes diana de PIF1a en tomate son distintos a los identificados previamente en Arabidopsis. Todos estos datos en conjunto sugieren que PIF1a y, en mucho menor grado, PIF1b comparten algunas funciones con su homólogo PIF1 de Arabidopsis, pero también ilustran que se han producido eventos de neofuncionalización en tomate. Al hacer esto, la evolución ha podido utilizar el potencial de estos factores de transcripción para regular nuevos procesos específicos en este cultivo de interés agronómico.<br>Light is one of the most important environmental cues influencing the plant life cycle. Plants have developed a set of complex molecular mechanisms that sense changes in light quality and quantity. PHYTOCHROME INTERACTING FACTORs (PIFs) are transcription factors that interact with the photoreceptors phytochromes (phy) and mediate the responses to red/far-red light. PIFs are involved in the regulation of a broad range of developmental processes. They have been extensively studied in Arabidopsis thaliana, but very little is known about their roles in other species. In this thesis, we investigate the role of the two homologs of PIF1 found in tomato (Solanum lycopersicum): PIF1a and PIF1b. The analysis of PIF1a and PIF1b expression showed very different patterns, indicating a potential evolutionary divergence in their roles. Protein stability experiments in red and far-red light unveiled that PIF1b has lost its ability to interact with PhyB, while PIF1a is still able to do it, confirming the evolutionary divergence hypothesis. On the other hand, tomato genome editing by CRISPR-Cas9 generated pif1a and pif1b loss-of-function lines, as well as double mutants pif1a pif1b. The phenotypic characterization of these mutants showed that both transcription factors are involved in the regulation of seed germination, synthesis of leaf pigments during de-etiolation and fruit production. Other processes are regulated just by PIF1a, such as root hair elongation, synthesis of steroidal glycoalkaloids in leaves, flowering time and fruit growth and softening. We did not identify any process regulated specifically by PIF1b alone. Due to the central role of PIF1a, we decided to perform RNA-seq experiments in PIF1a-inducible lines. The results showed that the induction of PIF1a had a relatively minor impact in the transcriptomic profile, and that the putative gene targets of PIF1a in tomato were different from those previously identified in Arabidopsis. All this data together suggests that PIF1a and, to a much lower extent, PIF1b share some roles with Arabidopsis PIF1, but also illustrate that neofunctionalization has taken place in tomato. Doing this, evolution managed to use the potential of these transcription factors to regulate new specific processes in this crop of agronomic interest.