Role of the arbuscular mycorrhizal symbiosis on S-uptake and S-starvation resistance in Medicago truncatula

Abstract

International audienceDue to its key role in the biosynthesis of many S-containing compounds, sulphur is a macronutrient essential for plant growth, development, and response to various abiotic and biotic stresses. Sulphate represents a very small portion of soil S pull and it’s the only form that plant roots can take up and mobilize through H+-dependent co-transport processes implying sulphate transporters. Unlike the other organically bound forms of S, sulphate is normally leached from soils due to its solubility in water, thus reducing its availability to plants. Although our knowledge of plant sulphate transporters has been growing significantly in the last decades, little is still known about the effect of the arbuscular mycorrhiza (AM) interaction on S-uptake and S-stress resistance. For this reason our studies focused on the mycorrhizal interaction between the leguminous model plant Medicago truncatula and the arbuscular mycorrhizal fungus Rhizophagus intraradices (ex Glomus intraradices). Carbon, nitrogen and sulphur measurements in different plant tissues and expression analysis of genes encoding putative Medicago sulphate transporters (MtSULTRs) were performed to better understand the beneficial effects of mycorrhizal interaction at different sulphate concentrations. The putative effects of mycorrhizal interaction were also assessed on seed weight and quality through protein content and 1-D gel analyses. Among the 8 putative MtSULTRs in-silico identified; some of them were differentially transcribed in roots and leaves due to sulphate concentration and/or upon mycorrhization, potentially defining a switch between direct (DP) and mycorrhizal (MP) sulphate uptake pathways