Interactions Pisum sativum – Pseudomonas : conséquences sur la nutrition en fer, la croissance et l’immunité de la plante hôte

The project aimed at making progress in the knowledge of the iron-mediated interactions between pea and fluorescent pseudomonads in order to promote the iron-nutrition and health of the host-plant. A bibliographical study was conducted to draw up the state of the art concerning the influence of rhizosphere microorganisms on plant iron status (Chapter 1).Pisum sativum has been chosen as an agronomic model-plant because of its high potential in agroecology and in Human nutrition related to its ability to fix atmospheric nitrogen and to the high amino-acids content of its seeds. However, this species suffers from a high susceptibility to iron deficiency as expressed by the well-known chlorosis symptom. The goal is to value pseudomonad’s siderophores through the promotion of pea iron-nutrition and health.The strategy used consisted in evaluating (i) the influence of two pea cultivars, tolerant (T) and susceptible (S) to iron chlorosis, on the diversity of fluorescent pseudomonads and of their siderophores (Chapter 2), and in return (ii) the variability of the beneficial effects of the siderophores according to their diversity at the level of the organism, and at the cellular and molecular levels. Bacteria, and siderophores representative of the described diversity, have been tested for (i) their antagonistic potential against a phytopathogen oomycete, Aphanomyces euteiches (Chapter 2), and (ii) their effects on the plant iron content and ionome (Chapter 3). Mechanisms involved in the beneficial effects, with a specific focus on the impact of the model-siderophores on iron homeostasis and regulation of the growth/defense balance, have been studied by analyzing (i) siderophore transport in planta of a model-siderophore at the cellular level (Chapter 4), and (ii) transcripts of genes involved in iron acquisition, homeostasis, regulation of the growth/defense balance and plant defense response, at the molecular level.Finally, the implications of these findings are discussed in a conclusive part.À travers cette étude, l’importance des interactions entre la plante et les microorganismes du sol liées à la dynamique du fer dans la rhizosphère a été mise en évidence. Plus particulièrement, l'objectif a été de déterminer le rôle des bactéries appartenant au groupe des Pseudomonas spp. fluorescents et de leurs sidérophores (sids) majoritaires, les pyoverdines (pvds), dans la nutrition en fer et l'immunité du pois (Pisum sativum), une plante à fort intérêt en agroécologie et pour l'alimentation.La stratégie choisie a été d’étudier l'effet de la plante sur les microorganismes et, en retour, des microorganismes sur la plante. Deux cultivars de pois, l'un sensible (S), et l'autre tolérant (T), à la chlorose ferrique ont été étudiés afin de dégager des hypothèses de la comparaison des données acquises. La pvdC7R12 modèle utilisée dans plusieurs études antérieures, et A. thaliana, ont également été intégrées à ce travail pour progresser dans la connaissance des mécanismes impliqués dans les interactions étudiées

Pisum sativum – Pseudomonas interactions : influence on iron nutrution, growth and immunity of the host plant

À travers cette étude, l’importance des interactions entre la plante et les microorganismes du sol liées à la dynamique du fer dans la rhizosphère a été mise en évidence. Plus particulièrement, l'objectif a été de déterminer le rôle des bactéries appartenant au groupe des Pseudomonas spp. fluorescents et de leurs sidérophores (sids) majoritaires, les pyoverdines (pvds), dans la nutrition en fer et l'immunité du pois (Pisum sativum), une plante à fort intérêt en agroécologie et pour l'alimentation.La stratégie choisie a été d’étudier l'effet de la plante sur les microorganismes et, en retour, des microorganismes sur la plante. Deux cultivars de pois, l'un sensible (S), et l'autre tolérant (T), à la chlorose ferrique ont été étudiés afin de dégager des hypothèses de la comparaison des données acquises. La pvdC7R12 modèle utilisée dans plusieurs études antérieures, et A. thaliana, ont également été intégrées à ce travail pour progresser dans la connaissance des mécanismes impliqués dans les interactions étudiées.The project aimed at making progress in the knowledge of the iron-mediated interactions between pea and fluorescent pseudomonads in order to promote the iron-nutrition and health of the host-plant. A bibliographical study was conducted to draw up the state of the art concerning the influence of rhizosphere microorganisms on plant iron status (Chapter 1).Pisum sativum has been chosen as an agronomic model-plant because of its high potential in agroecology and in Human nutrition related to its ability to fix atmospheric nitrogen and to the high amino-acids content of its seeds. However, this species suffers from a high susceptibility to iron deficiency as expressed by the well-known chlorosis symptom. The goal is to value pseudomonad’s siderophores through the promotion of pea iron-nutrition and health.The strategy used consisted in evaluating (i) the influence of two pea cultivars, tolerant (T) and susceptible (S) to iron chlorosis, on the diversity of fluorescent pseudomonads and of their siderophores (Chapter 2), and in return (ii) the variability of the beneficial effects of the siderophores according to their diversity at the level of the organism, and at the cellular and molecular levels. Bacteria, and siderophores representative of the described diversity, have been tested for (i) their antagonistic potential against a phytopathogen oomycete, Aphanomyces euteiches (Chapter 2), and (ii) their effects on the plant iron content and ionome (Chapter 3). Mechanisms involved in the beneficial effects, with a specific focus on the impact of the model-siderophores on iron homeostasis and regulation of the growth/defense balance, have been studied by analyzing (i) siderophore transport in planta of a model-siderophore at the cellular level (Chapter 4), and (ii) transcripts of genes involved in iron acquisition, homeostasis, regulation of the growth/defense balance and plant defense response, at the molecular level.Finally, the implications of these findings are discussed in a conclusive part

Interaction Pisum sativum (pois)- Pseudomonas : Conséquences sur la nutrition en fer, la croissance et l’immunité de la plante hôte

SPEEABIOMEDOCT INRALe projet vise à progresser dans notre connaissances des interactions pois – Pseudomonas afin d’améliorer la nutrition en fer et la santé de la plante-hôte. Le pois représente un fort potentiel en agroécologie (symbiose fixatrice d’azote) et en nutrition humaine (graines riches en acides aminés). Cependant, sa culture est sensible à la carence en fer et à certains phytopathogènes. Pour promouvoir la nutrition en fer et la santé du pois, l’objectif est de valoriser les pyoverdines, sidérophores produits par les Pseudomonas spp. fluorescents, dont certains peuvent améliorer la nutrition en fer de plantes et sont responsables d’antagonisme envers des phytopathogènes. La stratégie consiste à évaluer (i) l’influence du génotype (cultivar) de pois sur la diversité de cette communauté bactérienne et de ses sidérophores et en retour (ii) la variabilité des effets bénéfiques des différents sidérophores sur la plante. Des sidérophores représentatifs de la diversité caractérisée seront testés pour leurs effets sur la croissance et la teneur en fer de la plante et pour leur potentiel antagoniste envers des phytopathogènes. L’effet de sidérophores modèles sur l’homéostasie du fer et la régulation de la balance croissance/défense de la plante, sera également étudié. Les recherches proposées doivent permettre in fine d’améliorer nos connaissances des mécanismes responsables des effets bénéfiques des sidérophores sur le pois et d’identifier des cultivars valorisant au mieux ces interactions

Importance of the Rhizosphere Microbiota in Iron Biofortification of Plants

International audienceIncreasing the iron content of plant products and iron assimilability represents a major issue for human nutrition and health. This is also a major challenge because iron is not readily available for plants in most cultivated soils despite its abundance in the Earth’s crust. Iron biofortification is defined as the enhancement of the iron content in edible parts of plants. This biofortification aims to reach the objectives defined by world organizations for human nutrition and health while being environment friendly. A series of options has been proposed to enhance plant iron uptake and fight against hidden hunger, but they all show limitations. The present review addresses the potential of soil microorganisms to promote plant iron nutrition. Increasing knowledge on the plant microbiota and plant-microbe interactions related to the iron dynamics has highlighted a considerable contribution of microorganisms to plant iron uptake and homeostasis. The present overview of the state of the art sheds light on plant iron uptake and homeostasis, and on the contribution of plant-microorganism (plant-microbe and plant-plant-microbe) interactions to plant nutritition. It highlights the effects of microorganisms on the plant iron status and on the co-occurring mechanisms, and shows how this knowledge may be valued through genetic and agronomic approaches. We propose a change of paradigm based on a more holistic approach gathering plant and microbial traits mediating iron uptake. Then, we present the possible applications in plant breeding, based on plant traits mediating plant-microbe interactions involved in plant iron uptake and physiology

Influence of pea genotype on root associated fluorescent pseudomonads, consequences for plant iron nutrition

International audiencePea has a high potential in agroecology because of its ability to fix atmospheric nitrogen and in Human nutrition because of the high aminoacid content of its grains. However, pea may suffer from a susceptibility to iron deficiency in calcareous soils. This susceptibility varies depending on cultivars. Pseudomonad siderophores, pyoverdines (pvd), were shown to promote iron nutrition in Arabidopsis and tobacco. Thus, we hypothesize that variations in iron susceptibility between pea cultivars could be related to differences in their ability to recruit fluorescent pseudomonad (fp) contributing to siderophore-mediated iron nutrition. Our aims were to compare i) the impact of a susceptible (S) and a tolerant (T) cultivar of pea on fp biodiversity with a focus on their pvd, and in return ii) the impact of the corresponding bacteria and pvd on pea iron nutrition. The strategy consisted in cultivating S & T pea cultivars in a calcareous soil (low iron bioavailability). fp associated with roots of S & T and corresponding pvd were compared. In return, representative pvd from fp associated with S and T were tested for i) their effect on the transcription of genes involved in plant iron uptake and homeostasis (rt-qPCR) and ii) their impact on plant growth, iron content and ionome (HRICP-MS). Differences recorded between fp associated with T and S roots were related to i) their low susceptibility to Fe deficiency and ii) their pvd types as characterized by isoelectrofocalisation. Representatives of major pvd types impacted differently S & T for i) iron content, plant ionome and growth of pea and ii) the transcription of genes involved in plant iron metabolism. The results obtained support the principle of an extended phenotype in which associated bacteria contribute to plant nutrition, showing the importance to consider root microbiota to develop strategies aiming at overcoming iron susceptibility in pea. Further studies are in progress to unravel the mechanisms implied

Report on the interaction between pea and fluorescent pseudomonads and the potential impact on the plant iron nutrition

National audienc

Influence of pea genotype on root-associated pseudomonads, impact on the plant protection against fungal pathogens

National audienc

Contribution of fluorescent pseudomonads to iron nutrition and health of pea

National audienc

Influence of pea genotype on root-associated pseudomonads, impact on the plant protection against fungal pathogens

National audienc

Interactions between <em>Pisum sativum</em> & pseudomonads, consequences on plant iron nutrition and growth and immunity

National audiencePea has a high potential in agroecology, however, it may suffer from a susceptibility to iron deficiency in calcareous soils. This susceptibility varies depending on cultivars. Pseudomonad siderophores, pyoverdines (pvd), were shown to promote iron nutrition in Arabidopsis and tobacco. The hypothesis was therefore raised that variation in iron susceptibility between pea cultivars could be related to differences in their ability to recruit fluorescent pseudomonads (fp) contributing to siderophore-mediated iron nutrition. Our aims were to compare i) the impact of a susceptible (S) and a tolerant (T) cultivar of pea on fp biodiversity with a focus on their pvd, and in return ii) the impact of the corresponding bacteria and pvd on pea iron growth and nutrition. fp associated with roots of S & T and corresponding pvd were compared. In return, representative pvd were tested for their impact on plant growth, iron content and ionome (HRICP-MS). Differences recorded between fp associated with T and S roots were related to i) their low susceptibility to Fe deficiency and ii) their pvd types as characterized by isoelectrofocalisation. Representatives of major pvd types impacted differently S & T iron content, plant ionome and growth. The results obtained support the principle of an extended phenotype in which associated bacteria contribute to plant nutrition, showing the importance to consider root microbiota to develop strategies aiming at overcoming iron susceptibility in pea