Caractérisation fonctionnelle des gènes Sl-IAA3 et Sl-hls chez la tomate. Rôle dans le dialogue entre l'auxine et l'éthylène

Le développement des plantes est le résultat d'une coordination complexe entre de multiples signaux endogènes essentiellement hormonaux et exogènes issus de l'environnement. En particulier, l'intégration des différentes voies de signalisation hormonales est modulée de manière organe-dépendante. Mon projet de thèse s'inscrit dans ce cadre et vise à identifier les acteurs moléculaires du dialogue hormonal entre l'éthylène et l'auxine. L'interaction entre l’éthylène et l'auxine est l'exemple choisi dans cette étude en raison du rôle prépondérant joué par ces deux hormones dans les processus de maturation et de développement des fruits. En premier lieu, la caractérisation fonctionnelle du gène Sl-IAA3 codant pour un régulateur transcriptionnel apparenté à la famille des Aux/IAA de tomate a montré que la sous-expression de ce gène engendre des phénotypes associés à la fois à l'auxine (altération de la dominance apicale) et à l'éthylène (exagération du crochet apical et réduction de l'epinastie foliaire). Ces résultats révèlent pour la première fois que le gène Sl-IAA3 se trouve au centre du dialogue entre les voies de signalisation de l'auxine et de l'éthylène. La formation du crochet apical constitue un système bien adapté à l'étude du dialogue hormonal en raison du rôle déjà démontré de l'auxine et l'éthylène dans ce processus. L'étude réalisée ici montre qu'en plus de l'altération du crochet apical, le mutant hls1 présente des phénotypes nouveaux associés à la lumière, au glucose et à l'ABA. Deux orthologues (Sl-HLS1 et Sl-HLS2) du gène At-HLS1 d'Arabidopsis ont été isolés chez la tomate et leur validation fonctionnelle a été réalisée par complémentation du mutant hls1 d'Arabidopsis. L'étude de l'expression tissulaire montre que Sl-HLS2 s'exprime au niveau de la face convexe du crochet apical à l'opposé de Sl-IAA3 dont l'expression est associée à la face concave. Ce résultat suggère que Sl-IAA3 et Sl-HLS2 pourraient avoir des fonctions antagonistes sur l'élongation cellulaire aux niveaux interne et externe du crochet permettant ainsi la formation de la boucle. Au total, la caractérisation de deux gènes intervenant à la croisée des voies de signalisation de l'auxine et l'éthylène réalisée ici sur des tissus végétatifs, fournit de nouveaux outils pour aborder à l'avenir le rôle du dialogue hormonal dans le développement et la maturation des fruits. ABSTRACT : Plant development and survival depend on the ability of these organisms to integrate many signalling which enables them to produce an appropriate response. Ethylene and auxin are phytohormones known to regulate agonistly or antagonistly many processes of plant development but yet the key integrating molecular players remain largely undiscovered. My Ph.D project deals with the identification and characterization of molecular actors that take part in this dialogue. We report that Sl-IAA3, a member of the tomato auxin/indole-3-acetic acid (Aux/IAA) gene family, is an intersection point between auxin and ethylene signal transduction pathways. Aux/IAA genes encode short-lived transcriptional regulators that mediate auxin responses. Sl-IAA3 expression is controlled by both auxin and ethylene and is regulated on a tight tissue-specific basis. Downregulation of Sl-IAA3 via an antisense strategy results in auxin and ethylenerelated phenotypes including altered apical dominance, lower auxin sensitivity, exaggerated apical hook curvature in the dark and reduced petiole epinasty in the light. These ethylene-related phenotypes in the antisense tomato lines (AS-IAA3) position Sl-IAA3 firmly at the crossroads between auxin and ethylene signalling in tomato. The induction of apical hook offers an excellent system to study auxinethylene interplay. In Arabidopsis, ethylene acts through HOOKLESS (HLS1) to control hook formation through modulating differential cell elongation in opposite sides of the hook. Loss of function mutation in the HLS1 gene results in the absence of hook even in the presence of exogenous ethylene. In the present study, we extended the phenotypes of the Arabidopsis hls1 mutant to alteration of light sensitivity, glucose and ABA tolerance and gravitropic growth thus uncovering the importance of HLS gene in the integration of multiple signalling pathways. Two functional tomato hookless genes (Sl-HLS1 and Sl-HLS2) were isolated in this study and shown to positively complement the Arabidopsis hls1 mutant. Expression of Sl-HLS2 in the hook is restricted to the outer face, opposite to Sl-IAA3 whose expression is localized in the inner face of the hook curvature. The data suggest that Sl-HLS2 and Sl-IAA3 exert antagonist control of cell elongation in the inner and outer part of the apical hook. Overall, the two genes characterized in this study open new prospects towards addressing the role of ethylene and auxin cross-talk during fruit development and ripening

Functional characterization of tomato Sl-IAA3 and Sl-hls genes‎. Role in auxin and ethylene cross-talk

Plant development and survival depend on the ability of these organisms to integrate many signalling which enables them to produce an appropriate response. Ethylene and auxin are phytohormones known to regulate agonistly or antagonistly many processes of plant development but yet the key integrating molecular players remain largely undiscovered. My Ph.D project deals with the identification and characterization of molecular actors that take part in this dialogue. We report that Sl-IAA3, a member of the tomato auxin/indole-3-acetic acid (Aux/IAA) gene family, is an intersection point between auxin and ethylene signal transduction pathways. Aux/IAA genes encode short-lived transcriptional regulators that mediate auxin responses. Sl-IAA3 expression is controlled by both auxin and ethylene and is regulated on a tight tissue-specific basis. Downregulation of Sl-IAA3 via an antisense strategy results in auxin and ethylenerelated phenotypes including altered apical dominance, lower auxin sensitivity, exaggerated apical hook curvature in the dark and reduced petiole epinasty in the light. These ethylene-related phenotypes in the antisense tomato lines (AS-IAA3) position Sl-IAA3 firmly at the crossroads between auxin and ethylene signalling in tomato. The induction of apical hook offers an excellent system to study auxinethylene interplay. In Arabidopsis, ethylene acts through HOOKLESS (HLS1) to control hook formation through modulating differential cell elongation in opposite sides of the hook. Loss of function mutation in the HLS1 gene results in the absence of hook even in the presence of exogenous ethylene. In the present study, we extended the phenotypes of the Arabidopsis hls1 mutant to alteration of light sensitivity, glucose and ABA tolerance and gravitropic growth thus uncovering the importance of HLS gene in the integration of multiple signalling pathways. Two functional tomato hookless genes (Sl-HLS1 and Sl-HLS2) were isolated in this study and shown to positively complement the Arabidopsis hls1 mutant. Expression of Sl-HLS2 in the hook is restricted to the outer face, opposite to Sl-IAA3 whose expression is localized in the inner face of the hook curvature. The data suggest that Sl-HLS2 and Sl-IAA3 exert antagonist control of cell elongation in the inner and outer part of the apical hook. Overall, the two genes characterized in this study open new prospects towards addressing the role of ethylene and auxin cross-talk during fruit development and ripening

Particle swarm optimization for support vector clustering Separating hyper-plane of unlabeled data

International audienceThe objective of this work is to design a new method to solve the problem of integrating the Vapnik theory, as regards support vector machines, in the field of clustering data. For this we turned to bio-inspired meta-heuristics. Bio-inspired approaches aim to develop models resolving a class of problems by drawing on patterns of behavior developed in ethology. For instance, the Particle Swarm Optimization (PSO) is one of the latest and widely used methods in this regard. Inspired by this paradigm we propose a new method for clustering. The proposed method PSvmC ensures the best separation of the unlabeled data sets into two groups. It aims specifically to explore the basic principles of SVM and to combine it with the meta-heuristic of particle swarm optimization to resolve the clustering problem. Indeed, it makes a contribution in the field of analysis of multivariate data. Obtained results present groups as homogeneous as possible. Indeed, the intra-class value is more efficient when comparing it to those obtained by Hierarchical clustering, Simple K-means and EM algorithms for different database of benchmark

Peptide encoding Populus CLV3/ESR-RELATED 47 (PttCLE47) promotes cambial development and secondary xylem formation in hybrid aspen

The CLAVATA3 (CLV3)/EMBRYO SURROUNDING REGION (ESR)-RELATED (CLE) peptide ligands in connection with their receptors are important players in cell-to-cell communications in plants. Here, we investigated the function of the Populus CLV3/ESR-RELATED 47 (PttCLE47) gene during secondary growth and wood formation in hybrid aspen (Populus tremula x tremuloides) using an RNA interference (RNAi) approach. Expression of PttCLE47 peaks in the vascular cambium. Silencing of the PttCLE47 gene expression affected lateral expansion of stems and decreased apical height growth and leaf size. In particular, PttCLE47 RNAi trees exhibited a narrower secondary xylem zone with less xylem cells/cell file. The reduced radial growth phenotype also correlated with a reduced number of cambial cell layers. In agreement with these results, expression of several cambial regulator genes was downregulated in the stems of the transgenic trees in comparison with controls. Altogether, these results suggest that the PttCLE47 gene is a major positive regulator of cambial activity in hybrid aspen, mainly promoting the production of secondary xylem. Furthermore, in contrast to previously characterized CLE genes expressed in the wood-forming zone, PttCLE47 appears to be active at its site of expression.Peer reviewe

Interest of the therapeutic education in patients with type 2 diabetes observing the fast of Ramadan

AbstractThe fast of Ramadan is a dilemma for diabetic patients due to the complexity of the management of diabetes during this holy month and the multiple risks they face (hypoglycemia, etc.).ObjectivesEvaluate the impact of a structured protocol of therapeutic education in a sample of type 2 diabetes, who were authorized by their doctors to fast, on metabolic and anthropometric profiles.MethodsThis prospective study was conducted among 54 type 2 diabetic patients (28 men and 26 women) aged 36–65years, recruited from National Nutrition Institute. Patients were divided into two groups: the first group (n=26) received an education session one to two weeks before the month of Ramadan; the second group (n=28) did not have appropriate therapeutic education except therapeutic adjustments. All our diabetic patients benefited from anthropometric measurements, determination of body composition and metabolic assessment (HbA1c, cholesterol, triglycerides, etc.) before and after the month of Ramadan.ResultsThe fast was completed without complications in 25 diabetic patients educated group and 22 control patients.We found that weight loss was greater among educated diabetic patients (−1.05kg) than in controls (−0.58kg), but without statistical significance. Body composition has not undergone significant changes in both diabetic groups.Therapeutic education has led to a decline of 0.27% in HbA1c in the educated group while glycemic control in diabetic patients uneducated remained stable. Furthermore, we observed a better lipid profile in diabetic patients educated than those who did not have education.ConclusionOur results justify the interest of patient education centered on the month of Ramadan in all type 2 diabetic patients observing the fast of the holy month. This education should be continued during Ramadan in order to fulfill this religious rite safely

Sl-IAA3, a tomato Aux/IAA at the crossroads of auxin and ethylene signalling involved in differential growth

Whereas the interplay of multiple hormones is essential for most plant developmental processes, the key integrating molecular players remain largely undiscovered or uncharacterized. It is shown here that a member of the tomato auxin/indole-3-acetic acid (Aux/IAA) gene family, Sl-IAA3, intersects the auxin and ethylene signal transduction pathways. Aux/IAA genes encode short-lived transcriptional regulators central to the control of auxin responses. Their functions have been defined primarily by dominant, gain-of-function mutant alleles in Arabidopsis. The Sl-IAA3 gene encodes a nuclear-targeted protein that can repress transcription from auxin-responsive promoters. Sl-IAA3 expression is auxin and ethylene dependent, is regulated on a tight tissue-specific basis, and is associated with tissues undergoing differential growth such as in epinastic petioles and apical hook. Antisense down-regulation of Sl-IAA3 results in auxin and ethylene-related phenotypes, including altered apical dominance, lower auxin sensitivity, exaggerated apical hook curvature in the dark and reduced petiole epinasty in the light. The results provide novel insights into the roles of Aux/IAAs and position the Sl-IAA3 protein at the crossroads of auxin and ethylene signalling in tomato

Caractérisation fonctionnelle des gènes Sl-IAA3 et Sl-hls chez la tomate (Rôle dans le dialogue entre l'auxine et l'éthylène)

Plant development and survival depend on the ability of these organisms to integrate many signalling which enables them to produce an appropriate response. Ethylene and auxin are phytohormones known to regulate agonistly or antagonistly many processes of plant development but yet the key integrating molecular players remain largely undiscovered. My Ph.D project deals with the identification and characterization of molecular actors that take part in this dialogue. We report that Sl-IAA3, a member of the tomato auxin/indole-3-acetic acid (Aux/IAA) gene family, is an intersection point between auxin and ethylene signal transduction pathways. Aux/IAA genes encode short-lived transcriptional regulators that mediate auxin responses. Sl-IAA3 expression is controlled by both auxin and ethylene and is regulated on a tight tissue-specific basis. Downregulation of Sl-IAA3 via an antisense strategy results in auxin and ethylenerelated phenotypes including altered apical dominance, lower auxin sensitivity, exaggerated apical hook curvature in the dark and reduced petiole epinasty in the light. These ethylene-related phenotypes in the antisense tomato lines (AS-IAA3) position Sl-IAA3 firmly at the crossroads between auxin and ethylene signalling in tomato. The induction of apical hook offers an excellent system to study auxinethylene interplay. In Arabidopsis, ethylene acts through HOOKLESS (HLS1) to control hook formation through modulating differential cell elongation in opposite sides of the hook. Loss of function mutation in the HLS1 gene results in the absence of hook even in the presence of exogenous ethylene. In the present study, we extended the phenotypes of the Arabidopsis hls1 mutant to alteration of light sensitivity, glucose and ABA tolerance and gravitropic growth thus uncovering the importance of HLS gene in the integration of multiple signalling pathways. Two functional tomato hookless genes (Sl-HLS1 and Sl-HLS2) were isolated in this study and shown to positively complement the Arabidopsis hls1 mutant. Expression of Sl-HLS2 in the hook is restricted to the outer face, opposite to Sl-IAA3 whose expression is localized in the inner face of the hook curvature. The data suggest that Sl-HLS2 and Sl-IAA3 exert antagonist control of cell elongation in the inner and outer part of the apical hook. Overall, the two genes characterized in this study open new prospects towards addressing the role of ethylene and auxin cross-talk during fruit development and ripening.Le développement des plantes est le résultat d une coordination complexe entre de multiples signaux endogènes essentiellement hormonaux et exogènes issus de l'environnement. En particulier, l'intégration des différentes voies de signalisation hormonales est modulée de manière organe-dépendante. Mon projet de thèse s inscrit dans ce cadre et vise à identifier les acteurs moléculaires du dialogue hormonal entre l éthylène et l auxine. L interaction entre l éthylène et l auxine est l exemple choisi dans cette étude en raison du rôle prépondérant joué par ces deux hormones dans les processus de maturation et de développement des fruits. En premier lieu, la caractérisation fonctionnelle du gène Sl-IAA3 codant pour un régulateur transcriptionnel apparenté à la famille des Aux/IAA de tomate a montré que la sous-expression de ce gène engendre des phénotypes associés à la fois à l'auxine (altération de la dominance apicale) et à l'éthylène (exagération du crochet apical et réduction de l epinastie foliaire). Ces résultats révèlent pour la première fois que le gène Sl-IAA3 se trouve au centre du dialogue entre les voies de signalisation de l'auxine et de l'éthylène. La formation du crochet apical constitue un système bien adapté à l étude du dialogue hormonal en raison du rôle déjà démontré de l auxine et l éthylène dans ce processus. L'étude réalisée ici montre qu'en plus de l'altération du crochet apical, le mutant hls1 présente des phénotypes nouveaux associés à la lumière, au glucose et à l ABA. Deux orthologues (Sl-HLS1 et Sl-HLS2) du gène At-HLS1 d'Arabidopsis ont été isolés chez la tomate et leur validation fonctionnelle a été réalisée par complémentation du mutant hls1 d Arabidopsis. L'étude de l'expression tissulaire montre que Sl-HLS2 s exprime au niveau de la face convexe du crochet apical à l'opposé de Sl-IAA3 dont l expression est associée à la face concave. Ce résultat suggère que Sl-IAA3 et Sl-HLS2 pourraient avoir des fonctions antagonistes sur l élongation cellulaire aux niveaux interne et externe du crochet permettant ainsi la formation de la boucle. Au total, la caractérisation de deux gènes intervenant à la croisée des voies de signalisation de l auxine et l éthylène réalisée ici sur des tissus végétatifs, fournit de nouveaux outils pour aborder à l'avenir le rôle du dialogue hormonal dans le développement et la maturation des fruits.TOULOUSE-ENSAT-Documentation (315552324) / SudocSudocFranceF

Tomato Aux/IAA3 and HOOKLESS are important actors of the interplay between auxin and ethylene during apical hook formation

Plants implement differential cell growth as an adaptation process in order to direct their development in a way that allow them to better cope with the environmental conditions. This process requires the complex integration of multiple hormone signalings, though, a lot remain to be known about the mechanisms and the molecular actors that take part in this hormonal dialogue. We have previously shown that Sl-IAA3, an Aux/IAA gene, is a molecular link between auxin and ethylene responses in tomato plants. We show here that the expression of Sl-IAA3 in etiolated seedlings is restricted to the inner side of the apical hook, opposite to that of the HOOKLESS gene whose loss-offunction mutation results in the absence of hook formation. We propose a model on how auxin and ethylene modulate the expression of Auxin Response Factor 2 (ARF2) via IAA3 and HLS protein to regulate hypocotyl bending