27 research outputs found
The Pseudomonas fluorescens siderophore pyoverdine weakens arabidopsis thaliana defense in favor of growth in iron-deficient conditions
Pyoverdines are siderophores synthesized by fluorescent Pseudomonas spp. Under iron-limiting conditions, these high-affinity ferric iron chelators are excreted by bacteria in the soil to acquire iron. Pyoverdines produced by beneficial Pseudomonas spp. ameliorate plant growth. Here, we investigate the physiological incidence and mode of action of pyoverdine from Pseudomonas fluorescens C7R12 on Arabidopsis (Arabidopsis thaliana) plants grown under iron-sufficient or iron-deficient conditions. Pyoverdine was provided to the medium in its iron-free structure (apo-pyoverdine), thus mimicking a situation in which it is produced by bacteria. Remarkably, apo-pyoverdine abolished the iron-deficiency phenotype and restored the growth of plants maintained in the iron-deprived medium. In contrast to a P. fluorescens C7R12 strain impaired in apo-pyoverdine production, the wild-type C7R12 reduced the accumulation of anthocyanins in plants grown in iron-deficient conditions. Under this condition, apo-pyoverdine modulated the expression of around 2,000 genes. Notably, apo-pyoverdine positively regulated the expression of genes related to development and iron acquisition/redistribution while it repressed the expression of defense-related genes. Accordingly, the growth-promoting effect of apo-pyoverdine in plants grown under iron-deficient conditions was impaired in iron-regulated transporter1 and ferric chelate reductase2 knockout mutants and was prioritized over immunity, as highlighted by an increased susceptibility to Botrytis cinerea This process was accompanied by an overexpression of the transcription factor HBI1, a key node for the cross talk between growth and immunity. This study reveals an unprecedented mode of action of pyoverdine in Arabidopsis and demonstrates that its incidence on physiological traits depends on the plant iron status
Involvement of <em>Pseudomonas fluorescens</em> pyoverdine in growth, defence responses and iron homeostasis in <em>Arabidopsis thaliana</em>
National audienceIron, the fourth major element in the Earth crust, is essential for growth and development of living organisms. However, due to its low solubility in the soil, it is weakly available for plants and micro-organisms. To efficiently assimilate iron, living organisms have evolved specific strategies. In plants such as Arabidopsis thaliana three trans-membrane proteins are involved in iron assimilation while in bacteria such as Pseudomonas fluorescens iron is taken up from the soil thanks to molecules displaying high affinity for iron called siderophores. It has been recently shown that pyoverdine, the major siderophore of the beneficial bacterium Pseudomonas fluorescens, is assimilated by A. thaliana through an unknown mechanism. Interestingly, pyoverdine improves plant growth and iron nutrition. It is currently accepted that iron competition is a key event during plant infection by pathogenic micro-organisms. Furthermore, a protective role conferred to plants by several beneficial bacteriosiderophores against pathogens has been proposed. To investigate the global incidence of pyoverdine on plants, we decided to perform a microarray analysis. We identified plant genes whose expression is highly modulated by pyoverdine. These genes mainly encode proteins involved in iron homeostasis and in defense reactions. Further work will include pathogenicity tests using mutants affected in the expression of the genes of interest to understand their role in pyoverdine effects. These set of data will give us a first view of the incidence of pyoverdine in the plant physiology and its capacity to face pathogen attack
Les protĂ©ines S-nitrosylĂ©es lors des rĂ©ponses de dĂ©fense des plantes. Cas de la protĂ©ine CDC48 et de lâEPSP Synthase
Rapport de stage de Master 2 Recherche en Biochimie Biologie Cellulaire et Moléculaire (BBCM) SPE IPM CT non renseigné car non soutenu par INRAMaste
Establishment of tools for investigating pyoverdine impact on iron homeostasis and plant defence responses
National audienceIron, the fourth major element in the Earth crust, is essential for growth and development of living organisms. However, due to its low solubility in the soil, it is weakly available for plants and micro-organisms. To efficiently assimilate iron, living organisms have evolved specific strategies. In plants such as Arabidopsis thaliana three trans-membrane proteins are involved in iron assimilation while in bacteria such as Pseudomonas fluorescens iron is taken up from the soil thanks to molecules displaying high affinity for iron called siderophores. It has been recently shown that pyoverdine, the major siderophore of the beneficial bacterium Pseudomonas fluorescens, is assimilated by A. thaliana through an unknown mechanism. Interestingly, pyoverdine improves plant growth and iron nutrition. It is currently accepted that iron competition is a key event during plant infection by pathogenic micro-organisms. Furthermore, a protective role conferred to plants by several beneficial bacteriosiderophores against pathogens has been proposed. To investigate the global incidence of pyoverdine on plants, we decided to perform a microarray analysis. We identified plant genes whose expression is highly modulated by pyoverdine. These genes mainly encode proteins involved in iron homeostasis and in defense reactions. Further work will include pathogenicity tests using mutants affected in the expression of the genes of interest to understand their role in pyoverdine effects. These set of data will give us a first view of the incidence of pyoverdine in the plant physiology and its capacity to face pathogen attack
Incidence physiologique et étude du mode d'action de la pyoverdine de Pseudomonas fluorescens chez Arabidopsis thaliana : liens avec l'homéostasie du fer, la croissance et les défenses
Siderophores are strong iron chelators produced by bacteria under iron deficiency conditions. In the present work, we studied the impact of the siderophore pyoverdine, produced by the plant growth promoting rhizobacteria Pseudomonas fluorescens C7R12, on plant physiology from phenotypic to molecular effects with a specific focus on plant growth, immune response and iron homeostasis. Based on our analysis of the mode of action of the non-protein amino acid ÎČ-aminobutyric acid (BABA), a priming inducer in plants, we studied more specifically the functional link between iron homeostasis and plant immunity. Under iron deficiency, P. fluorescens excretes the iron free form of pyoverdine (apo-pyo) in the soil. Once chelated with iron (ferri-pyo), the complex is internalized by the bacteria. We demonstrated that Arabidopsis thaliana plants treated by apo-pyo in a medium containing or not iron (Fe 25 or Fe 0) also internalize pyoverdine. Moreover, we observed that under iron deficiency, pyoverdine treated plants did not display the growth reduction induced by iron deficiency. In accordance with this phenotype, a microarray analysis revealed that the expression of genes related to growth and development was induced, as well as genes related to iron uptake and transport in planta. In contrast, the down regulation of the expression of genes related to defense was observed. Correspondingly, we demonstrated that the growth improvement induced by apo-pyo under iron deficiency depends on the expression of IRT1 and FRO2, two major genes involved in iron uptake mechanisms. Of interest, the resistance to Botrytis cinerea conferred by iron deficiency was lost following apo-pyo treatment. The overexpression of the HBI1 transcription factor, known to be involved in the growth-defense tradeoff, can be linked to the above observations. These apo-pyo effects were not observed after treatment of plants under sufficient iron conditions, indicating that in A. thaliana apo-pyo effects are dependent on the plant iron status. In the same time, the analysis of the mode of action of BABA that potentiates plant defense responses demonstrated that BABA is a powerful iron chelator. BABA treatment in A. thaliana triggered a transient iron deficiency response. Based on this assessment, we assume that iron deficiency response and priming of defense may be connected. In accordance with this hypothesis, we showed that plants cultivated under iron deficiency and BABA treated plants both displayed resistance to B. cinerea and produced secondary metabolites associated to defense. Hence, the BABA priming effects on plant defense may be due to the induction of transient iron deficiency. To conclude, this work draws first explications on pyoverdine effects on plant physiology and presents an original mode of action contributing to the priming effects of BABA. In a larger view, this work supports the recent concept of the existence of a cross-regulation between growth, immunity and iron homeostasis in plants.Ce travail sâinscrit dans lâĂ©tude de lâincidence de sidĂ©rophores sur la physiologie de la plante. Il dĂ©crit plus prĂ©cisĂ©ment, Ă lâĂ©chelle phĂ©notypique et molĂ©culaire, lâimpact de la pyoverdine produite par la souche bactĂ©rienne bĂ©nĂ©fique Pseudomonas fluorescens C7R12 sur la croissance, la rĂ©ponse immunitaire et lâhomĂ©ostasie du fer chez Arabidopsis thaliana. Le lien fonctionnel entre immunitĂ© et homĂ©ostasie du fer a Ă©tĂ© abordĂ© de façon plus spĂ©cifique via lâanalyse du mode dâaction de lâacide ÎČ-aminobutyrique (BABA), un potentialisateur des rĂ©ponses de dĂ©fense de la plante.En conditions de fer limitantes, afin de pourvoir Ă la carence, Pseudomonas fluorescens libĂšre la pyoverdine dans le sol sous sa forme non chĂ©latĂ©e (apo-pyo). Le complexe fer-pyoverdine (ferri-pyo) est ensuite internalisĂ© par la bactĂ©rie. Nous avons vĂ©rifiĂ© que lâapo-pyo est assimilĂ©e par des plantes dâA. thaliana cultivĂ©es dans un milieu contenant ou non du fer. De façon remarquable, lâapo-pyo restaure le phĂ©notype de croissance des plantes carencĂ©es en fer. Une analyse transcriptomique a rĂ©vĂ©lĂ© que chez ces derniĂšres, lâapo-pyo induit fortement lâexpression de gĂšnes associĂ©s Ă la croissance, lâimport et la redistribution du fer in planta. En revanche, une rĂ©pression de lâexpression de gĂšnes de dĂ©fense sâopĂšre. De façon concordante, lâeffet promoteur de croissance de lâapo-pyo chez les plantes carencĂ©es est strictement dĂ©pendant de lâexpression des gĂšnes IRT1 et FRO2 codant deux protĂ©ines majeures de lâimport de fer. De plus, une moindre rĂ©sistance de ces plantes Ă Botrytis cinerea a Ă©tĂ© relevĂ©e. Lâincidence nĂ©gative de lâapo-pyo sur les dĂ©fenses sâaccompagne dâune surexpression du facteur de transcription HBI1 jouant un rĂŽle clĂ© dans la rĂ©gulation de la balance croissance/dĂ©fense. Lâensemble de ces Ă©vĂ©nements nâa pas Ă©tĂ© observĂ© chez les plantes cultivĂ©es dans un milieu enrichi en fer, dĂ©montrant que les effets de lâapo-pyo chez A. thaliana sont conditionnĂ©s par le statut en fer de la plante. En parallĂšle, lâĂ©tude du mode dâaction du BABA a indiquĂ© que ce potentialisateur de lâimmunitĂ© est un chĂ©lateur trĂšs efficace du fer. En consĂ©quence, appliquĂ© Ă des plantes dâA. thaliana, le BABA dĂ©clenche une carence en fer transitoire. Nous avons Ă©mis lâhypothĂšse que cette carence pourrait constituer un signal plaçant la plante en veille dĂ©fensive. En accord avec cette assomption, les plantes carencĂ©es en fer prĂ©sentent une rĂ©sistance accrue Ă B. cinerea et produisent des mĂ©tabolites secondaires associĂ©s aux dĂ©fenses dont lâaccumulation est Ă©galement induite par le BABA. Ainsi, la carence en fer transitoire occasionnĂ©e par le BABA pourrait constituer lâune des composantes de son effet potentialisateur sur lâimmunitĂ©. En conclusion, ce travail apporte des premiers Ă©lĂ©ments explicatifs quant Ă lâincidence de la pyoverdine sur des traits physiologiques de la plante et rapporte un mode dâaction orignal du BABA. Plus gĂ©nĂ©ralement, il renforce le concept encore naissant de lâexistence de rĂ©gulations croisĂ©es entre les voies de signalisation associĂ©es Ă la croissance, lâimmunitĂ© et lâhomĂ©ostasie du fer chez les plantes
Investigation of the physiological impact and the mode of action of the pyoverdine from Pseudomonas fluorescens on Arabidopsis thaliana : links with iron homeostasis, growth and defense
Ce travail sâinscrit dans lâĂ©tude de lâincidence de sidĂ©rophores sur la physiologie de la plante. Il dĂ©crit plus prĂ©cisĂ©ment, Ă lâĂ©chelle phĂ©notypique et molĂ©culaire, lâimpact de la pyoverdine produite par la souche bactĂ©rienne bĂ©nĂ©fique Pseudomonas fluorescens C7R12 sur la croissance, la rĂ©ponse immunitaire et lâhomĂ©ostasie du fer chez Arabidopsis thaliana. Le lien fonctionnel entre immunitĂ© et homĂ©ostasie du fer a Ă©tĂ© abordĂ© de façon plus spĂ©cifique via lâanalyse du mode dâaction de lâacide ÎČ-aminobutyrique (BABA), un potentialisateur des rĂ©ponses de dĂ©fense de la plante. En conditions de fer limitantes, afin de pourvoir Ă la carence, Pseudomonas fluorescens libĂšre la pyoverdine dans le sol sous sa forme non chĂ©latĂ©e (apo-pyo). Le complexe fer-pyoverdine (ferri-pyo) est ensuite internalisĂ© par la bactĂ©rie. Nous avons vĂ©rifiĂ© que lâapo-pyo est assimilĂ©e par des plantes dâA. thaliana cultivĂ©es dans un milieu contenant ou non du fer. De façon remarquable, lâapo-pyo restaure le phĂ©notype de croissance des plantes carencĂ©es en fer. Une analyse transcriptomique a rĂ©vĂ©lĂ© que chez ces derniĂšres, lâapo-pyo induit fortement lâexpression de gĂšnes associĂ©s Ă la croissance, lâimport et la redistribution du fer in planta. En revanche, une rĂ©pression de lâexpression de gĂšnes de dĂ©fense sâopĂšre. De façon concordante, lâeffet promoteur de croissance de lâapo-pyo chez les plantes carencĂ©es est strictement dĂ©pendant de lâexpression des gĂšnes IRT1 et FRO2 codant deux protĂ©ines majeures de lâimport de fer. De plus, une moindre rĂ©sistance de ces plantes Ă Botrytis cinerea a Ă©tĂ© relevĂ©e. Lâincidence nĂ©gative de lâapo-pyo sur les dĂ©fenses sâaccompagne dâune surexpression du facteur de transcription HBI1 jouant un rĂŽle clĂ© dans la rĂ©gulation de la balance croissance/dĂ©fense. Lâensemble de ces Ă©vĂ©nements nâa pas Ă©tĂ© observĂ© chez les plantes cultivĂ©es dans un milieu enrichi en fer, dĂ©montrant que les effets de lâapo-pyo chez A. thaliana sont conditionnĂ©s par le statut en fer de la plante. En parallĂšle, lâĂ©tude du mode dâaction du BABA a indiquĂ© que ce potentialisateur de lâimmunitĂ© est un chĂ©lateur trĂšs efficace du fer. En consĂ©quence, appliquĂ© Ă des plantes dâA. thaliana, le BABA dĂ©clenche une carence en fer transitoire. Nous avons Ă©mis lâhypothĂšse que cette carence pourrait constituer un signal plaçant la plante en veille dĂ©fensive. En accord avec cette assomption, les plantes carencĂ©es en fer prĂ©sentent une rĂ©sistance accrue Ă B. cinerea et produisent des mĂ©tabolites secondaires associĂ©s aux dĂ©fenses dont lâaccumulation est Ă©galement induite par le BABA. Ainsi, la carence en fer transitoire occasionnĂ©e par le BABA pourrait constituer lâune des composantes de son effet potentialisateur sur lâimmunitĂ©. En conclusion, ce travail apporte des premiers Ă©lĂ©ments explicatifs quant Ă lâincidence de la pyoverdine sur des traits physiologiques de la plante et rapporte un mode dâaction orignal du BABA. Plus gĂ©nĂ©ralement, il renforce le concept encore naissant de lâexistence de rĂ©gulations croisĂ©es entre les voies de signalisation associĂ©es Ă la croissance, lâimmunitĂ© et lâhomĂ©ostasie du fer chez les plantes.Siderophores are strong iron chelators produced by bacteria under iron deficiency conditions. In the present work, we studied the impact of the siderophore pyoverdine, produced by the plant growth promoting rhizobacteria Pseudomonas fluorescens C7R12, on plant physiology from phenotypic to molecular effects with a specific focus on plant growth, immune response and iron homeostasis. Based on our analysis of the mode of action of the non-protein amino acid ÎČ-aminobutyric acid (BABA), a priming inducer in plants, we studied more specifically the functional link between iron homeostasis and plant immunity. Under iron deficiency, P. fluorescens excretes the iron free form of pyoverdine (apo-pyo) in the soil. Once chelated with iron (ferri-pyo), the complex is internalized by the bacteria. We demonstrated that Arabidopsis thaliana plants treated by apo-pyo in a medium containing or not iron (Fe 25 or Fe 0) also internalize pyoverdine. Moreover, we observed that under iron deficiency, pyoverdine treated plants did not display the growth reduction induced by iron deficiency. In accordance with this phenotype, a microarray analysis revealed that the expression of genes related to growth and development was induced, as well as genes related to iron uptake and transport in planta. In contrast, the down regulation of the expression of genes related to defense was observed. Correspondingly, we demonstrated that the growth improvement induced by apo-pyo under iron deficiency depends on the expression of IRT1 and FRO2, two major genes involved in iron uptake mechanisms. Of interest, the resistance to Botrytis cinerea conferred by iron deficiency was lost following apo-pyo treatment. The overexpression of the HBI1 transcription factor, known to be involved in the growth-defense tradeoff, can be linked to the above observations. These apo-pyo effects were not observed after treatment of plants under sufficient iron conditions, indicating that in A. thaliana apo-pyo effects are dependent on the plant iron status. In the same time, the analysis of the mode of action of BABA that potentiates plant defense responses demonstrated that BABA is a powerful iron chelator. BABA treatment in A. thaliana triggered a transient iron deficiency response. Based on this assessment, we assume that iron deficiency response and priming of defense may be connected. In accordance with this hypothesis, we showed that plants cultivated under iron deficiency and BABA treated plants both displayed resistance to B. cinerea and produced secondary metabolites associated to defense. Hence, the BABA priming effects on plant defense may be due to the induction of transient iron deficiency. To conclude, this work draws first explications on pyoverdine effects on plant physiology and presents an original mode of action contributing to the priming effects of BABA. In a larger view, this work supports the recent concept of the existence of a cross-regulation between growth, immunity and iron homeostasis in plants
Involvement of Pseudomonas fluorescens pyoverdine in growth, defence responses and iron homeostasis in Arabidopsis thaliana
Iron, the fourth major element in the Earth crust, is essential for growth and development of living organisms. However, due to its low solubility in the soil, it is weakly available for plants and micro-organisms. To efficiently assimilate iron, living organisms have evolved specific strategies. In plants such as Arabidopsis thaliana three trans-membrane proteins are involved in iron assimilation while in bacteria such as Pseudomonas fluorescens iron is taken up from the soil thanks to molecules displaying high affinity for iron called siderophores. It has been recently shown that pyoverdine, the major siderophore of the beneficial bacterium Pseudomonas fluorescens, is assimilated by A. thaliana through an unknown mechanism. Interestingly, pyoverdine improves plant growth and iron nutrition. It is currently accepted that iron competition is a key event during plant infection by pathogenic micro-organisms. Furthermore, a protective role conferred to plants by several beneficial bacteriosiderophores against pathogens has been proposed. To investigate the global incidence of pyoverdine on plants, we decided to perform a microarray analysis. We identified plant genes whose expression is highly modulated by pyoverdine. These genes mainly encode proteins involved in iron homeostasis and in defense reactions. Further work will include pathogenicity tests using mutants affected in the expression of the genes of interest to understand their role in pyoverdine effects. These set of data will give us a first view of the incidence of pyoverdine in the plant physiology and its capacity to face pathogen attack
Rhizobacteria-mediated activation of the Fe deficiency response in Arabidopsis roots : Impact on Fe status and signaling
The beneficial root-colonizing rhizobacterium Pseudomonas simiae WCS417 stimulates plant growth and induces systemic resistance against a broad spectrum of plant diseases. In Arabidopsis thaliana (Arabidopsis), the root transcriptional response to WCS417 shows significant overlap with the root response to iron (Fe) starvation, including activation of the marker genes MYB72 and IRT1. Here, we investigated how colonization of Arabidopsis roots by WCS417 impacts Fe homeostasis in roots and shoots. Under Fe-sufficient conditions, root colonization by WCS417 induced a transient Fe deficiency response in the root and elevated both the total amount of Fe in the shoot and the shoot fresh weight. When plants were grown under Fe-starvation conditions, WCS417 still promoted plant growth, but did not increase the total amount of Fe, resulting in chlorosis. Thus, increased Fe uptake in response to WCS417 is essential to maintain Fe homeostasis in the more rapidly growing plant. As the WCS417-induced Fe deficiency response is known to require a shoot-derived signal, we tested whether the Fe deficiency response is activated in response to an increased Fe demand in the more rapidly growing shoot. Exogenous application of Fe to the leaves to reduce a potential shoot Fe shortage did not prevent WCS417-mediated induction of the Fe deficiency response in the roots. Moreover, the leaf Fe status-dependent shoot-to-root signaling mutant opt3-2, which is impaired in the phloem-specific Fe transporter OPT3, still up-regulated the Fe deficiency response genes MYB72 and IRT1 in response to WCS417. Collectively, our results suggest that the WCS417-induced Fe deficiency response in the root is controlled by a shoot-to-root signaling system that functions independently of both leaf Fe status and OPT3