The role of organellar CGFS containing glutaredoxins in iron-sulfur clusters assembly and biogenesis in plants – FeSGrx

Iron sulphur proteins are required for many essential processes for life, such as photosynthesis, respiration or nitrogen and sulphur assimilation. Nevertheless, the different pathways involved in iron sulphur assembly and biogenesis in plants are poorly described, although some proteins homologous to those of bacterial, yeast and mammalian assembly machineries have been identified and sometimes characterized. Among those proteins, it has been demonstrated in Saccharomyces cerevisiae, that a glutaredoxin, a small ubiquitous oxidoreductase generally involved in the reduction of disulfide bonds, was implicated in this process but its role still needs to be clearly established. This data together with the identification of a [2Fe-2S] cluster bridged into glutaredoxin holodimers in two other unrelated organisms (poplar and human) suggested that the function of these glutaredoxin could be conserved between kingdoms. In higher plants, nearly 30 different Grx isoforms can be classified into three distinct subgroups which differ essentially by their active site sequences. Four proteins, homologous to the S. cerevisiae Grx previously identified, belong to the same subgroup and possess a strictly conserved CGFS active site. A few structural and biochemical studies have been carried out on CGFS containing glutaredoxins from E. coli and S. cerevisiae, but they were only performed with apo-proteins and no evidence was presented for the presence of an iron sulphur cluster in these proteins. Our objective is thus to develop a new project concerning the role of the CGFS containing glutaredoxins in iron sulfur biogenesis in photosynthetic organisms and to understand among this subgroup which glutaredoxin(s) is (are) involved in this process and in which cell compartment as two different assembly systems are present in plant mitochondria and chloroplasts. For this purpose, we will develop a functional genomic and multidisciplinary approach using two model plants (poplar and Arabidopsis) and four work packages. The first one deals with the characterization of both gene and protein expression and of protein localization. Using a recombinant protein technology, we will have access to the biochemical and structural properties of these Grxs. A proteomic approach will also be developed in order to try to identify new protein partners of this class of glutaredoxin. Finally, biochemical and reverse genetic approaches will help to evaluate the function of glutaredoxins in iron sulfur biogenesis in plants, but these results could possibly also be extended to other organisms.