0000000001056623
AUTHOR
Agnès Robin
Iron acquisition from Fe-pyoverdine by Arabidopsis thaliana.
Taking into account the strong iron competition in the rhizosphere and the high affinity of pyoverdines for Fe(III), these molecules are expected to interfere with the iron nutrition of plants, as they do with rhizospheric microbes. The impact of Fe-pyoverdine on iron content of Arabidopsis thaliana was compared with that of Fe-EDTA. Iron chelated to pyoverdine was incorporated in a more efficient way than when chelated to EDTA, leading to increased plant growth of the wild type. A transgenic line of A. thaliana overexpressing ferritin showed a higher iron content than the wild type when supplemented with Fe-EDTA but a lower iron content when supplemented with Fe-pyoverdine despite its inc…
Reciprocal interactions between plants and fluorescent pseudomonads in relation to iron in the rhizosphere
SPE EA Section 15 : Engineering the rhizosphere: The "biased rhizosphere" concept Ouvrage en 2 volumes Résumé du livre : Molecular Microbial Ecology of the Rhizosphere covers current knowledge on the molecular basis of plant-microbe interactions in the rhizosphere. Also included in the book are both reviews and research-based chapters describing experimental materials and methods. Edited by a leader in the field, with contributions from authors around the world, Molecular Microbial Ecology of the Rhizosphere brings together the most up-to-date research in this expanding area, and will be a valuable resource for molecular microbiologists and plant soil scientists, as well as upper level stud…
Fluorescent pseudomonads harboring type III secretion genes are enriched in the mycorrhizosphere of Medicago truncatula
Type III secretion systems (T3SSs) of Gram-negative bacteria mediate direct interactions with eukaryotic cells. Pseudomonas spp. harboring T3SS genes (T3SS+) were previously shown to be more abundant in the rhizosphere than in bulk soil. To discriminate the contribution of roots and associated arbuscular mycorrhizal fungi (AMF) on the enrichment of T3SS+ fluorescent pseudomonads in the rhizosphere of Medicago truncatula, their frequency was assessed among pseudomonads isolated from mycorrhizal and nonmycorrhizal roots and from bulk soil. T3SS genes were identified by PCR targeting a conserved hrcRST DNA fragment. Polymorphism of hrcRST in T3SS+ isolates was assessed by PCR-restriction fragm…
Diversity of root-associated fluorescent pseudomonads as affected by ferritin overexpression in tobacco
A transgenic tobacco overexpressing ferritin (P6) was recently shown to accumulate more iron than the wild type (WT), leading to a reduced availability of iron in the rhizosphere and shifts in the pseudomonad community. The impact of the transgenic line on the community of fluorescent pseudomonads was assessed. The diversity of 635 isolates from rhizosphere soils, rhizoplane + root tissues, and root tissues of WT and P6, and that of 98 isolates from uncultivated soil was characterized. Their ability to grow under iron stress conditions was assessed by identifying their minimal inhibitory concentrations of 8-hydroxyquinoline for each isolate, pyoverdine diversity by isoelectrofocusing and ge…
Implication of pyoverdines in the interactions of fluorescent pseudomonads with soil microflora and plant in the rhizosphere
Soils are known to be oligotrophic environments whereas soil microflora is mostly heterotrophic in such way that microbial growth in soil is mainly limited by the scarce sources of readily available organic compounds (Wardle 1992). Therefore, in soils, microflora is mostly in stasis (fungistasis/bacteriostasis) (Lockwood 1977). In counterpart, plants are autotrophic organisms responsible for the primary production resulting from the photosynthesis. A significant part of photosynthetates are released from plant roots to the soil through a process called rhizodeposition. These products, i.e. the rhizodeposits, are made of exudates, lysates, mucilage, secretions and dead cell material, as well…
Evidence de l'adaptation des communautés microbiennes sédimentaires de rivière à la minéralisation du diuron: influence du ruissellement et de l'érosion des sols
International audience; Purpose Surface runoff and erosion are major drivers of pesticide transport from soils to rivers draining vineyard watersheds. A recent study showed that applications of diuron on vineyards and diuron dispersal could lead to microbial adaptation to diuron biodegradation from treated soils to the receiving hydrosystem. Given the limited knowledge on microbial adaptation to pesticide degradation in aquatic environments, we conducted a microcosm study designed to assess the impact of runoff and erosion processes on the adaptation of riverine-sediment microbial communities to diuron mineralization. Materials and methods The experimental laboratory set-up consisted in aqu…
Toward an integrated approach for studying plant-microbe interactions in the rhizosphere: from genomic to proteomic
International audience
Effect of ferritin overexpression in tobacco on the structure of bacterial and pseudomonad communities associated with the roots
The genetic structures of total bacterial and pseudomonad communities were characterized in rhizosphere soil and rhizoplane+root tissues of tobacco wild type and a ferritin overexpressor transgenic line (P6) by a cultivation-independent method using directly extracted DNA at the end of three consecutive plant cultures. The structure of total bacterial communities was characterized by automated ribosomal intergenic spacer analysis (A-RISA), and that of pseudomonad communities was characterized by PCR-restriction fragment length polymorphism (PCR-RFLP) from DNA amplified with specific primers. The structure of total bacterial communities was significantly modified in the rhizosphere soil by t…
Chapter 4 Iron Dynamics in the Rhizosphere
Abstract Iron is an essential micronutrient for most organisms due to its role in fundamental metabolic processes. In cultivated soils, soil solution iron is mostly oxidized [Fe(III) species] unless local anoxic conditions develop. The concentration of these Fe(III) species is small in soil solution due to the low solubility of ferric oxides, oxyhydroxides, and hydroxides, which is minimal at neutral and alkaline pH. In the rhizosphere, iron concentration in the soil solution is even lower because of its uptake by aerobic organisms (plants and microorganisms), leading to a high level of competition for Fe(III). In order to face iron competition, these organisms have evolved active uptake st…
Interactions durables entre plantes et microorganismes dans les sols
National audience
Reciprocal interactions between plants and fluorescent pseudomonads in relation with iron in the rhizosphere
communication orale invitée; absent
Implication of pyoverdines in the interactions of fluorescent pseudomonads with soil microflora and plant in the rhizosphere
International audience
Reciprocal interactions between plants and fluorescent pseudomonads in relation with iron in the rhizosphere
National audience; Although iron is the fourth element in the Earth’s crust, the availability of Fe(III) is limited in most cultivated soils due to their pH. In soil adhering to plant roots (rhizosphere), plants release a sgnificant part of their photosynthetates (rhizodeposits) that promote microbial density and activity. Iron uptake by this microflora and by plant roots contributes to decrease even more iron availability in the rhizosphere. In this competition context, plants and microbes have developed active strategies of iron uptake. In dicotyledon plants, this strategy involves (i) the excretion of protons, (ii) the reduction of Fe(III) by reductases, and (iii) plasmalemma transport o…
Reciprocal interactions between plants and fluorescent pseudomonads in relation with iron in the rhizosphere
International audience; Iron is an essential element for plants and microbes. However, in most cultivated soils, the concentration of iron available for these living organisms is very low since its solubility is controlled by stable hydroxides, oxyhydroxides and oxides. The high demand for iron by plants and microorganisms in the rhizosphere together with its low availability in soils leads to a strong competition for this nutrient among living organisms. To face this competition, plants and microorganisms have developed active strategies of iron uptake. In non graminaceous plants (strategy I), iron uptake relies on acidification and reduction of Fe+++ in Fe++ which incorporated in the root…