Résumé
Among the mineral nutrients that are required for plant metabolism, iron (Fe) and sulfur (S) play a central role, as both nutrients are necessary for the activity of several proteins involved in major cellular processes (e.g.photosynthesis, respiration, etc.). Considering that, worldwide, Fe shortage arises in one third of the cultivated land, and that the frequency of soils displaying S deficiency is increasing (decrease of anthropogenic S release), there is an increasing interest in understanding how Fe and S homeostasis are interconnected in plants. Such knowledge being necessary if one aims at sustaining plant growth and productivity in such limited environment without the use of exogenous fertilizers. By using various molecular, physiological and biochemical approaches, and Arabidopsis thaliana as model plant, we have investigated how S deficiency affects the plant response to Fe shortage and how this signal is integrated into the regulatory network controlling Fe deficiency responses. We found that S deficiency was (i) antagonising Fe deficiency symptoms at the whole plant level, (ii) modulating the expression of key regulatory proteins involved in the transcriptional regulatory cascade controlling Fe homeostasis and (iii)involving yet uncharacterized molecular actors.