23 research outputs found
Auxin Perception Is Required for Arbuscule Development in Arbuscular Mycorrhizal Symbiosis
Most land plant species live in symbiosis with arbuscular mycorrhizal fungi. These fungi differentiate essential functional structures called arbuscules in root cortical cells from which mineral nutrients are released to the plant. We investigated the role of microRNA393 (miR393), an miRNA that targets several auxin receptors, in arbuscular mycorrhizal root colonization. Expression of the precursors of the miR393 was down-regulated during mycorrhization in three different plant species: Solanum lycopersicum, Medicago truncatula, and Oryza sativa. Treatment of S. lycopersicum, M. truncatula, and O. sativa roots with concentrations of synthetic auxin analogs that did not affect root development stimulated mycorrhization, particularly arbuscule formation. DR5-GUS, a reporter for auxin response, was preferentially expressed in root cells containing arbuscules. Finally, overexpression of miR393 in root tissues resulted in down-regulation of auxin receptor genes (transport inhibitor response1 and auxin-related F box) and underdeveloped arbuscules in all three plant species. These results support the conclusion that miR393 is a negative regulator of arbuscule formation by hampering auxin perception in arbuscule-containing cells
Auxin Perception Is Required for Arbuscule Development in Arbuscular Mycorrhizal Symbiosis
<em>NODULE ROOT</em> and <em>COCHLEATA</em> Maintain Nodule Development and Are Legume Orthologs of Arabidopsis <em>BLADE-ON-PETIOLE</em> Genes
During their symbiotic interaction with rhizobia, legume plants develop symbiosis-specific organs on their roots, called nodules, that house nitrogen-fixing bacteria. The molecular mechanisms governing the identity and maintenance of these organs are unknown. Using Medicago truncatula nodule root (noot) mutants and pea (Pisum sativum) cochleata (coch) mutants, which are characterized by the abnormal development of roots from the nodule, we identified the NOOT and COCH genes as being necessary for the robust maintenance of nodule identity throughout the nodule developmental program. NOOT and COCH are Arabidopsis thaliana BLADE-ON-PETIOLE orthologs, and we have shown that their functions in leaf and flower development are conserved in M. truncatula and pea. The identification of these two genes defines a clade in the BTB/POZ-ankyrin domain proteins that shares conserved functions in eudicot organ development and suggests that NOOT and COCH were recruited to repress root identity in the legume symbiotic organ
CaractĂ©risation des gĂšnes MtNOOT et PsCOCH chez Medicago truncatula et Pisum sativum : deux rĂ©gulateurs polyvalents du dĂ©veloppement vĂ©gĂ©tal recrutĂ©s pour lâidentitĂ© de la nodositĂ© symbiotique
Les plantes de la famille des lĂ©gumineuses ont la particularitĂ© dâhĂ©berger intracellulairement des bactĂ©ries du sol communĂ©ment appelĂ©es rhizobia. Cette interaction symbiotique se dĂ©roule au sein de la nodositĂ©, un organe formĂ© de-novo au niveau racinaire. LâactivitĂ© nitrogĂ©nase bactĂ©rienne y permet la rĂ©duction de lâazote atmosphĂ©rique en NH3 assimilable par la plante. Si les mĂ©canismes molĂ©culaires gouvernant la reconnaissance entre les deux partenaires, lâinfection intracellulaire et lâorganogĂ©nĂšse des nodositĂ©s ont Ă©tĂ© particuliĂšrement bien dĂ©crits au cours des derniĂšres dĂ©cennies ; peu dâinformations sont quant Ă elles disponibles sur lâorigine de ce programme morphogĂ©nĂ©tique nouveau chez les Angiospermes. Les nodositĂ©s des deux lĂ©gumineuses modĂšles Medicago truncatula et Pisum sativum sont qualifiĂ©es dâindĂ©terminĂ©es en raison de la persistance dâun mĂ©ristĂšme en position apicale. Les nodositĂ©s des mutants noot (nodule-root) chez M. truncatula et coch (cochleata) chez le pois dĂ©veloppent des racines ectopiques Ă partir des tissus vasculaires des nodositĂ©s, montrant ainsi que les nodositĂ©s et racines sont plus apparentĂ©es que leur simple comparaison anatomique ne pouvait le suggĂ©rer. En outre, lâactivitĂ© mĂ©rsitĂ©matique des nodositĂ©s est fortement perturbĂ©e chez ces deux mutants qui prĂ©sentent des nodositĂ©s multilobĂ©es et Ă©largies. Nous avons montrĂ© que les gĂšnes MtNOOT et PsCOCHLEATA Ă©taient orthologues aux gĂšnes AtBLADE-ON-PETIOLE1 et 2 qui codent deux activateurs transcriptionels redondants et cruciaux pour la rĂ©gulation de nombreux processus dĂ©veloppementaux chez Arabidopsis thaliana. En raison de la forte conservation des fonctions biologiques des protĂ©ines NOOT, BOPs et COCH, notamment pour la rĂ©gulation de la morphologie foliaire et florale, de lâarchitecture de lâinflorescence et de la formation des zones dâabscission, nous proposons que ces fonctions reprĂ©sentent les fonctions ancestrales de la famille des gĂšnes NBCL (NOOT BOP COCH LIKE). LâĂ©tude de dĂ©terminants hormonaux et gĂ©nĂ©tiques du mĂ©ristĂšme racinaire dans les nodositĂ©s sauvages et mutantes noot ainsi que la caractĂ©risation de lâhomĂ©ose nodule/racine nous ont permis de dĂ©gager des parallĂšles importants entre les tissus pĂ©riphĂ©riques de la nodositĂ© et ceux de la racine. Nous proposons donc un modĂšle de dĂ©veloppement des tissus vasculaires de la nodositĂ© par co-option du programme racinaire dont la rĂ©pression est en partie assurĂ©e par NOOT.Legume plants are able to house intracellularly soil bacteria collectively called rhizobia. This symbiotic process takes place in a new organ generally formed on the host roots, the nodule. This interaction allows atmospheric nitrogen fixation to the benefit of the plant by using the bacterial nitrogenase activity. Despite an exhaustive description of molecular determinants of this interaction allowing partners recognition, intracellular accommodation and early nodule organogenesis, less is known about cell lineage and identity of the nodule morphogenetic pathway which is thought to represent a recent acquisition during Angiosperms evolution. Nodules from model legumes such as Medicago truncatula or Pisum sativum are described as indeterminate because of the persistence of a distal meristem. The noot (nodule-root) and coch (coch) mutants, in M. truncatula and P. sativum respectively, develop ectopic roots from the nodule vasculature, suggesting that roots and symbiotic nodules are more closely related than previously admitted based on their anatomical comparison. Moreover, the meristematic activity is strongly modified in noot and coch nodules that harbor numerous and enlarged lobes. We showed that NOOT and COCH are orthologs to AtBLADE-ON-PETIOLE1 and 2 redundant transcriptional activators that represent key regulators of versatile plant developmental processes in Arabidopsis thaliana. Because of the conservation of biological functions controlled by NOOT, BOPs and COCH proteins, in particular the regulation of leaf and floral morphologies, abscission zones formation and inflorescence architecture, we proposed that such functions are inherited from a NBCLs (NOOT BOP COCH LIKE) ancestral gene. Our studies of hormonal and genetic determinants of the root meristem in noot and wild-type nodules as well as the characterization of nodule-to-root homeosis have highlighted important parallels between nodule peripheral tissues and roots. We thus propose a model of nodule vascular unit maintenance by the NOOT-dependent repression of a co-opted root morphogenetic program
Plant microRNAs: key regulators of root architecture and biotic interactions
International audiencePlants have evolved a remarkable faculty of adaptation to deal with various and changing environmental conditions. In this context, the roots have taken over nutritional aspects and the root system architecture can be modulated in response to nutrient availability or biotic interactions with soil microorganisms. This adaptability requires a fine tuning of gene expression. Indeed, root specification and development are highly complex processes requiring gene regulatory networks involved in hormonal regulations and cell identity. Among the different molecular partners governing root development, microRNAs (miRNAs) are key players for the fast regulation of gene expression. miRNAs are small RNAs involved in most developmental processes and are required for the normal growth of organisms, by the negative regulation of key genes, such as transcription factors and hormone receptors. Here, we review the known roles of miRNAs in root specification and development, from the embryonic roots to the establishment of root symbioses, highlighting the major roles of miRNAs in these processes
Caractérisation des gÚnes MtNOOT et PsCOCH chez Medicago truncatula et Pisum sativum (deux régulateurs polyvalents du développement végétal recrutés pour l identité de la nodosité symbiotique)
Les plantes de la famille des légumineuses ont la particularité d héberger intracellulairement des bactéries du sol communément appelées rhizobia. Cette interaction symbiotique se déroule au sein de la nodosité, un organe formé de-novo au niveau racinaire. L activité nitrogénase bactérienne y permet la réduction de l azote atmosphérique en NH3 assimilable par la plante. Si les mécanismes moléculaires gouvernant la reconnaissance entre les deux partenaires, l infection intracellulaire et l organogénÚse des nodosités ont été particuliÚrement bien décrits au cours des derniÚres décennies ; peu d informations sont quant à elles disponibles sur l origine de ce programme morphogénétique nouveau chez les Angiospermes. Les nodosités des deux légumineuses modÚles Medicago truncatula et Pisum sativum sont qualifiées d indéterminées en raison de la persistance d un méristÚme en position apicale. Les nodosités des mutants noot (nodule-root) chez M. truncatula et coch (cochleata) chez le pois développent des racines ectopiques à partir des tissus vasculaires des nodosités, montrant ainsi que les nodosités et racines sont plus apparentées que leur simple comparaison anatomique ne pouvait le suggérer. En outre, l activité mérsitématique des nodosités est fortement perturbée chez ces deux mutants qui présentent des nodosités multilobées et élargies. Nous avons montré que les gÚnes MtNOOT et PsCOCHLEATA étaient orthologues aux gÚnes AtBLADE-ON-PETIOLE1 et 2 qui codent deux activateurs transcriptionels redondants et cruciaux pour la régulation de nombreux processus développementaux chez Arabidopsis thaliana. En raison de la forte conservation des fonctions biologiques des protéines NOOT, BOPs et COCH, notamment pour la régulation de la morphologie foliaire et florale, de l architecture de l inflorescence et de la formation des zones d abscission, nous proposons que ces fonctions représentent les fonctions ancestrales de la famille des gÚnes NBCL (NOOT BOP COCH LIKE). L étude de déterminants hormonaux et génétiques du méristÚme racinaire dans les nodosités sauvages et mutantes noot ainsi que la caractérisation de l homéose nodule/racine nous ont permis de dégager des parallÚles importants entre les tissus périphériques de la nodosité et ceux de la racine. Nous proposons donc un modÚle de développement des tissus vasculaires de la nodosité par co-option du programme racinaire dont la répression est en partie assurée par NOOT.Legume plants are able to house intracellularly soil bacteria collectively called rhizobia. This symbiotic process takes place in a new organ generally formed on the host roots, the nodule. This interaction allows atmospheric nitrogen fixation to the benefit of the plant by using the bacterial nitrogenase activity. Despite an exhaustive description of molecular determinants of this interaction allowing partners recognition, intracellular accommodation and early nodule organogenesis, less is known about cell lineage and identity of the nodule morphogenetic pathway which is thought to represent a recent acquisition during Angiosperms evolution. Nodules from model legumes such as Medicago truncatula or Pisum sativum are described as indeterminate because of the persistence of a distal meristem. The noot (nodule-root) and coch (coch) mutants, in M. truncatula and P. sativum respectively, develop ectopic roots from the nodule vasculature, suggesting that roots and symbiotic nodules are more closely related than previously admitted based on their anatomical comparison. Moreover, the meristematic activity is strongly modified in noot and coch nodules that harbor numerous and enlarged lobes. We showed that NOOT and COCH are orthologs to AtBLADE-ON-PETIOLE1 and 2 redundant transcriptional activators that represent key regulators of versatile plant developmental processes in Arabidopsis thaliana. Because of the conservation of biological functions controlled by NOOT, BOPs and COCH proteins, in particular the regulation of leaf and floral morphologies, abscission zones formation and inflorescence architecture, we proposed that such functions are inherited from a NBCLs (NOOT BOP COCH LIKE) ancestral gene. Our studies of hormonal and genetic determinants of the root meristem in noot and wild-type nodules as well as the characterization of nodule-to-root homeosis have highlighted important parallels between nodule peripheral tissues and roots. We thus propose a model of nodule vascular unit maintenance by the NOOT-dependent repression of a co-opted root morphogenetic program.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF
NIN Is Involved in the Regulation of Arbuscular Mycorrhizal Symbiosis
Arbuscular mycorrhizal (AM) symbiosis is an intimate and ancient symbiosis found between most of terrestrial plants and fungi from the Glomeromycota family. Later during evolution, the establishment of the nodulation between legume plants and soil bacteria known as rhizobia, involved several genes of the signalling pathway previously implicated for AM symbiosis. For the past years, the identification of the genes belonging to this Common Symbiotic Signalling Pathway have been mostly done on nodulation. Among the different genes already well identified as required for nodulation, we focused our attention on the involvement of Nodule Inception (NIN) in AM symbiosis. We show here that NIN expression is induced during AM symbiosis, and that the Medicago truncatula nin mutant is less colonized than the wild type M. truncatula strain. Moreover, nin mutant displays a defect in the ability to be infected by the fungus Rhizophagus irregularis. This work brings a new evidence of the common genes involved in overlapping signalling pathways of both nodulation and in AM symbiosis
miRNA-encoded peptides (miPEPs): A new tool to analyze the roles of miRNAs in plant biology
Des modÚles pour les sciences du végétal et à vocation agronomique
La comprĂ©hension des mĂ©canismes gĂ©nĂ©tiques, molĂ©culaires et physiologiques sous-tendant les grandes fonctions biologiques et les caractĂšres dâintĂ©rĂȘt agronomique chez les plantes Ă fleur reprĂ©sente un enjeu considĂ©rable. Les efforts se concentrent sur un nombre rĂ©duit de modĂšles prĂ©sentant des caractĂ©ristiques favorables et rĂ©unissant une masse critique de chercheurs et de moyens. Arabidopsis thaliana, le riz et Medicago truncatula sont ces modĂšles