Séminaire IBIP
Les séminaires ont lieu sur le Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)

Jeudi 13 septembre 2012
Amphi 206 (Cœur d’Ecole) à 14h

The biogenesis of Fe-S proteins in plants

Janneke Balk
John Innes Centre / University of East Anglia, Norwich Research Park, Colney, UK

Iron-sulphur (Fe-S) clusters are associated with at least 100 expressed plant proteins, including prevalent enzymes such as Photosystem I with three [4Fe-4S] clusters, [2Fe-2S] ferredoxins and aconitases. In addition, several novel Fe-S proteins have recently been discovered to play a role in DNA metabolism, such as helicases, DNA polymerases and primase. Based on genomic and functional studies, it has become apparent that plastids rely on the SUF system (for sulfur mobilization), while plant mitochondria harbour the ISC (for iron-sulphur cluster) assembly pathway. The pathways are largely conserved with those found in cyanobacteria and alpha-proteobacteria, respectively. The assembly process requires a cysteine desulfurase that transfers persulfide to a scaffold protein, concomitant with the incorporation of iron. The Fe-S cluster is then transferred to its destination protein with the help of chaperones and/or glutaredoxins. Cytosolic Fe-S enzymes are dependent on the mitochondrial , but not the plastid cysteine desulfurase. A mitochondrial ABC transporter, ATM3, is also required for cytosolic Fe-S enzymes (Bernard et al. 2009 Plant Physiol. 151, 590-602). In collaboration with the group of Xiaofeng Cui from the Shanghai Institute of Plant Physiology, we have shown that the phenotype of atm3 is much enhanced when combined with a non-lethal point mutation in AE7. We further show that the DUF59-family protein AE7 forms a protein complex with AtCIA1, AtNAR1 and AtMET18, the so called CIA targeting complex which is conserved in yeast and humans. While ATM3 is required for all cytosolic Fe-S proteins tested so far, AE7 is only required for a subset, including aconitases and the DNA glycosylase ROS1. Both atm3 and ae7 mutants have a cell cycle defect, increased DNA damage and induced expression of DNA repair genes. The results indicate that AE7 is a central member of the CIA pathway, linking plant mitochondria to nuclear genome integrity through assembly of Fe-S proteins.

Contact : Frédéric Gaymard

Contacts IBIP :
Sabine Zimmermann
Philippe Nacry
Christine Granier
Chantal Baracco