Résumé
Iron-sulfur (Fe-S) proteins have critical functions in plastids, participating notably in the photosynthetic electron transfer, sulfur and nitrogen assimilation, chlorophyll metabolism and vitamin or amino acid biosynthesis. Their maturation relies on the so-called SUF assembly machinery. The Fe-S clusters are synthesized de novo on a scaffold protein complex and then delivered to client proteins via several transfer proteins. However, the maturation pathways of most client proteins and their specificities towards transfer proteins are mostly unknown. In order to decipher the proteins interacting with the Fe-S cluster transfer protein NFU2, one of the three plastidial representatives found in Arabidopsis thaliana, we have performed a quantitative proteomic analysis of nfu2 plants (shoots, roots and seedlings). Combined with NFU2 co-immunoprecipitation and binary yeast two-hybrid experiments, we identified 14 new targets, among which nine were validated in planta using a binary bimolecular fluorescence complementation (BiFC) assay. These analyses also revealed a possible role for NFU2 in plant response to desiccation. Altogether this study delineates better the maturation pathways of many chloroplastic Fe-S proteins, extending considerably the number of NFU2 clients. It also helps clarifying the respective roles of the three NFU paralogs, NFU1, NFU2 and NFU3.