Etude du rôle des facteurs de transcription MtNF-YA1 et MtNF-YA2 dans les étapes précoces de la symbiose rhizobienne chez medicago truncatula

Les plantes de la famille des légumineuses sont capables d'établir une interaction symbiotique avec des bactéries du sol, collectivement appelées Rhizobia. Cette interaction aboutit à la formation d'un nouvel organe appelé nodule et dans lequel les bactéries différenciées fixent l'azote atmosphérique au bénéfice de la plante hôte. Les facteurs Nods (NFs) rhizobiens sont des molécules clés responsables de la spécificité d'hôte, et sont capables à eux seuls d'induire de nombreuses réponses développementales racinaires. MtNF-YA1 est un gène dont l'expression est fortement induite au cours du processus de nodulation chez Medicago truncatula. Ce gène code pour une sous-unité du complexe NF-Y, également appelé " CCAAT-Binding Factor " (CBF). Le facteur de transcription NF-Y est composé de trois sous-unités différentes appelées NF-YA, NF-YB, et NF-YC. Alors que chez les animaux, chaque sous-unité n'est généralement codée que par un seul gène, une diversification structurelle et fonctionnelle s'est produite chez les plantes, menant à l'apparition de familles multigéniques. Des analyses de plantes RNAi ou de mutants nf-ya1 ont précédemment montré que MtNF-YA1 est impliqué dans le maintien de l'activité méristématique nodulaire. Au cours de ma thèse, nous avons apporté l'évidence d'un rôle clé additionnel de MtNF-YA1 pendant l'infection rhizobienne. Nous avons de plus montré que MtNF-YA1 et son homologue MtNF-YA2 sont impliqués au cours de la voie de signalisation de réponse aux NFs menant à l'activation de l'expression du gène marqueur MtENOD11. En parallèle, l'étude de complexes trimériques NF-Y dans lesquels agissent NF-YA1 pour contrôler les étapes précoces de la nodulation a conduit à l'identification de partenaires potentiels NF-YB et NF-YC.Plants belonging to the legume family are able to establish a nitrogen fixation symbiosis with soil bacteria called Rhizobia, resulting in the formation of new organs called root nodules, in which differentiated bacteria fix atmospheric nitrogen to the benefit of the host plant. The bacterial Nod Factors (NFs) are known as key players responsible for the host specificity, and are able, in the absence of bacteria, to trigger many early plant responses. MtNF-YA1, in Medicago truncatula, is a gene whose expression is strongly up-regulated during the nodulation process. It encodes a subunit of the CCAAT-Binding Factor (CBF) also called NF-Y complex. The NF-Y transcription factor is composed of three different subunits (NF-YA, NF-YB and NF-YC). While in animals each NF-Y subunit is encoded by a single gene, a structural and functional diversification has occurred in plants, leading to the emergence of gene families. Using RNAi and mutant analyses, we previously showed that MtNF-YA1 is involved in the maintenance of the nodule meristematic activity. During my PhD, we provided evidences for the involvement of MtNF-YA1 during earlier stages of symbiotic root infection. We have shown that MtNF-YA1, together with the closely-related MtNF-YA2, is involved in the early NF signaling pathway leading to the activation of the MtENOD11 marker-gene. In parallel, the study of NF-Y trimeric complexes in which MtNF-YA1 acts to control early steps of nodulation led to the identification of potential NF-YB and NF-YC partners

Alternative Splicing Control of Abiotic Stress Responses

The deposited article is a post-print version and has been submitted to peer review.This publication hasn't any creative commons license associated.This deposit is composed by the main article, and it hasn't any supplementary materials associated.There is no public supplementary material available for this publication.Alternative splicing, which generates multiple transcripts from the same gene, is an important modulator of gene expression that can increase proteome diversity and regulate mRNA levels. In plants, this post-transcriptional mechanism is markedly induced in response to environmental stress, and recent studies have identified alternative splicing events that allow rapid adjustment of the abundance and function of key stress-response components. In agreement, plant mutants defective in splicing factors are severely impaired in their response to abiotic stress. Notably, mounting evidence indicates that alternative splicing regulates stress responses largely by targeting the abscisic acid (ABA) pathway. We review here current understanding of post-transcriptional control of plant stress tolerance via alternative splicing and discuss research challenges for the near future.Marie Skłodowska-Curie Individual Fellowship: (MSCA-IF-2015; grant 706274 ); EMBO Long-Term Fellowship: (ALTF 1576-2016 ); Fundação para a Ciência e a Tecnologia grant: (PTDC/BIA-PLA/1084/2014); GREEN-it research unit grant: (UID/Multi/04551/2013).info:eu-repo/semantics/publishedVersio

A phylogenetically conserved group of nuclear factor-Y transcription factors interact to control nodulation in legumes

The endosymbiotic association between legumes and soil bacteria called rhizobia leads to the formation of a new root-derived organ called the nodule in which differentiated bacteria convert atmospheric nitrogen into a form that can be assimilated by the host plant. Successful root infection by rhizobia and nodule organogenesis require the activation of symbiotic genes that are controlled by a set of transcription factors (TFs). We recently identified Medicago truncatula nuclear factor-YA1 (MtNF-YA1) and MtNF-YA2 as two M. truncatula TFs playing a central role during key steps of the Sinorhizobium meliloti-M. truncatula symbiotic interaction. NF-YA TFs interact with NF-YB and NF-YC subunits to regulate target genes containing the CCAAT box consensus sequence. In this study, using a yeast two-hybrid screen approach, we identified the NF-YB and NF-YC subunits able to interact with MtNF-YA1 and MtNF-YA2. In yeast (Saccharomyces cerevisiae) and in planta, we further demonstrated by both coimmunoprecipitation and bimolecular fluorescence complementation that these NF-YA, -B, and -C subunits interact and form a stable NF-Y heterotrimeric complex. Reverse genetic and chromatin immunoprecipitation-PCR approaches revealed the importance of these newly identified NF-YB and NF-YC subunits for rhizobial symbiosis and binding to the promoter of MtERN1 (for Ethylene Responsive factor required for Nodulation), a direct target gene of MtNF-YA1 and MtNF-YA2. Finally, we verified that a similar trimer is formed in planta by the common bean (Phaseolus vulgaris) NF-Y subunits, revealing the existence of evolutionary conserved NF-Y protein complexes to control nodulation in leguminous plants. This sheds light on the process whereby an ancient heterotrimeric TF mainly controlling cell division in animals has acquired specialized functions in plants.Instituto de Biotecnologia y Biologia Molecula

A phylogenetically conserved group of nuclear factor-Y transcription factors interact to control nodulation in legumes

The endosymbiotic association between legumes and soil bacteria called rhizobia leads to the formation of a new root-derived organ called the nodule in which differentiated bacteria convert atmospheric nitrogen into a form that can be assimilated by the host plant. Successful root infection by rhizobia and nodule organogenesis require the activation of symbiotic genes that are controlled by a set of transcription factors (TFs). We recently identified Medicago truncatula nuclear factor-YA1 (MtNF-YA1) and MtNF-YA2 as two M. truncatula TFs playing a central role during key steps of the Sinorhizobium meliloti-M. truncatula symbiotic interaction. NF-YA TFs interact with NF-YB and NF-YC subunits to regulate target genes containing the CCAAT box consensus sequence. In this study, using a yeast two-hybrid screen approach, we identified the NF-YB and NF-YC subunits able to interact with MtNF-YA1 and MtNF-YA2. In yeast (Saccharomyces cerevisiae) and in planta, we further demonstrated by both coimmunoprecipitation and bimolecular fluorescence complementation that these NF-YA, -B, and -C subunits interact and form a stable NF-Y heterotrimeric complex. Reverse genetic and chromatin immunoprecipitation-PCR approaches revealed the importance of these newly identified NF-YB and NF-YC subunits for rhizobial symbiosis and binding to the promoter of MtERN1 (for Ethylene Responsive factor required for Nodulation), a direct target gene of MtNF-YA1 and MtNF-YA2. Finally, we verified that a similar trimer is formed in planta by the common bean (Phaseolus vulgaris) NF-Y subunits, revealing the existence of evolutionary conserved NF-Y protein complexes to control nodulation in leguminous plants. This sheds light on the process whereby an ancient heterotrimeric TF mainly controlling cell division in animals has acquired specialized functions in plants.Instituto de Biotecnologia y Biologia Molecula

Étude du rôle des facteurs de transcription MtNF-YA1 et MtNF-YA2 dans les étapes précoces de la symbiose rhizobienne chez medicago truncatula

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

CCAAT-box binding transcription factors in plants: Y so many?

In the review article ‘CCAAT-box binding transcription factors in plants: Y so many’ by Tom Laloum, Stéphane De Mita, Pascal Gamas, Maël Baudin, and Andreas Niebel, which was published in the March 2013 issue of Trends in Plant Science, the procedure used for reconstructing the phylogenetic trees in Figure 2 was incorrectly described. The sentence ‘The tree has been reconstructed using maximum likelihood under the general time-reversible model as implemented in the PhyML software’ should read ‘The tree has been reconstructed using maximum likelihood under the LG model as implemented in the PhyML software’. This change to the figure legend does not affect the conclusions mentioned in the paper. Below is the corrected version of Figure 2: (voir PDF) Erratum, Trends in Plant Science, volume 18, issue 10, 594-595Transcription factors belonging to the CCAAT-box binding factor family (also known as the Nuclear Factor Y) are present in all higher eukaryotes. Studies in plants have revealed that each subunit of this heterotrimeric transcription factor is encoded by a gene belonging to a multigene family allowing a considerable modularity. In this review, we focus on recent findings concerning the expression patterns and potential functions of different members of these NF-Y protein families using a phylogenetic approach. During the course of evolution plant CCAAT-box binding factors seem to have diversified into at least two main groups. The first group has more general expression patterns and/or functions whereas the second group has acquired more specific expression patterns and/or functions and could play key roles in specific pathways

Two CCAAT box-binding transcription factors redundantly regulate early steps of the legume-rhizobia endosymbiosis

International audienceDuring endosymbiotic interactions between legume plants and nitrogen-fixing rhizobia, successful root infection by bacteria and nodule organogenesis requires the perception and transduction of bacterial lipo-chitooligosaccharidic signal called Nod factor (NF). NF perception in legume roots leads to the activation of an early signaling pathway and of a set of symbiotic genes which is controlled by specific early transcription factors (TFs) including CYCLOPS/IPD3, NSP1, NSP2, ERN1 and NIN. In this study, we bring convincing evidence that the Medicago truncatula CCAAT-box-binding NF-YA1 TF, previously associated with later stages of rhizobial infection and nodule meristem formation is, together with its closest homolog NF-YA2, also an essential positive regulator of the NF-signaling pathway. Here we show that NF-YA1 and NF-YA2 are both expressed in epidermal cells responding to NFs and their knock-down by reverse genetic approaches severely affects the NF-induced expression of symbiotic genes and rhizobial infection. Further over-expression, transactivation and ChIP-PCR approaches indicate that NF-YA1 and NF-YA2 function, at least in part, via the direct activation of ERN1. We thus propose a model in which NF-YA1 and NF-YA2 appear as early symbiotic regulators acting downstream of DMI3 and NIN and possibly within the same regulatory complexes as NSP1/2 to directly activate the expression of ERN1

A phylogenetically conserved group of NF-Y transcription factors interact to control nodulation in legumes

The endosymbiotic association between legumes and rhizobia leads to the formation of root nodules in which differentiated bacteria convert atmospheric nitrogen into a form that can be assimilated by the host plant. Successful root infection by rhizobia and nodule organogenesis require the activation of symbiotic genes that are controlled by a set of early transcription factors (TFs). MtNF-YA1 and MtNF-YA2 are two TFs playing partially redundant functions during several steps of the symbiotic interaction between Medicago truncatula and Sinorhizobium meliloti. NF-Y proteins are part of a transcriptional complex composed of three proteins (NF-YA, NF-YB and NF-YC) which bind DNA at CCAAT-boxes, a motif present in most eukaryotic promoters. In plants, each subunit is encoded by small gene families, potentially leading to a multitude of heterotrimeric NF-Y complexes. Here, using yeast two hybrid screenings, we identified the MtNF-YB and MtNF-YC subunits that interact with MtNF-YA1 and A2. Further, we confirmed, both in yeast and in planta, the formation of trimeric NF-Y complexes and showed that these complexes are functional during nodulation using reverse genetic approaches and ChIP-PCR. Finally, as orthologs of the characterized NF-Y subunits also control nodulation in other legumes, we showed in common bean that similar NF-Y trimers could form in planta. Our results suggest that we have identified a group of evolutionary conserved NF-Y proteins that interact to control nodulation in leguminous plants.Fil: Baudin, Maël. Centre National de la Recherche Scientifique; Francia. Centre de Recherche de Nantes. Institut National de la Recherche Agronomique; FranciaFil: Laloum, Tom. Centre National de la Recherche Scientifique; Francia. Centre de Recherche de Nantes. Institut National de la Recherche Agronomique; FranciaFil: Lepage, Agnes. Centre National de la Recherche Scientifique; Francia. Centre de Recherche de Nantes. Institut National de la Recherche Agronomique; FranciaFil: Rípodas, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Biotecnología y Biología Molecular. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Biotecnología y Biología Molecular; ArgentinaFil: Ariel, Federico Damian. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Centre D'etudes de Saclay; FranciaFil: Frances, Lisa. Centre National de la Recherche Scientifique; Francia. Centre de Recherche de Nantes. Institut National de la Recherche Agronomique; FranciaFil: Crespi, Martin. Centre D'etudes de Saclay; FranciaFil: Gamas, Pascal. Centre National de la Recherche Scientifique; FranciaFil: Blanco, Flavio Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Biotecnología y Biología Molecular. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Biotecnología y Biología Molecular; ArgentinaFil: Zanetti, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Biotecnología y Biología Molecular. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Biotecnología y Biología Molecular; ArgentinaFil: de Carvalho-Niebel, Fernanda. Centre National de la Recherche Scientifique; Francia. Centre de Recherche de Nantes. Institut National de la Recherche Agronomique; FranciaFil: Niebel, Andreas. Centre National de la Recherche Scientifique; Francia. Centre de Recherche de Nantes. Institut National de la Recherche Agronomique; Franci