Functional analysis of FRD3 in Arabidopsis

Zinc and iron are two essential micronutrients for plants. The homeostasis networks of the two metals are intertwined. The FRD3 (FERRIC REDUCTASE DEFECTIVE 3) protein, a member of the MATE family of membrane transporters, is a citrate transporter involved in iron homeostasis and playing a role in zinc tolerance in Arabidopsis. The FRD3 gene displays a complex regulation. Alternative transcript initiation for FRD3 determines two transcripts, which differ in their 5'UTRs and have differential translation efficiency. The two transcripts are selectively regulated under stress conditions: iron and zinc depletion, zinc excess or cadmium presence. We are aiming to determine the FRD3 function in zinc and iron homeostasis in Arabidopsis. We will present data (i) on the functional characterization of the alternative transcripts and their role in metal homeostasis in Arabidopsis and (ii) on the zinc phenotypes of the frd3 mutant.