Poster: Mineral nutrition

Abs # 201: Functional characterization of the Arabidopsis ferric chelate reductase (FRO) gene family.

Presenter:	Mukherjee, Indrani , indranic@mail.biol.sc.edu
Authors	Mukherjee, Indrani  (A)   Campbell, Nathan  (A)   Connolly, Erin L (A)
Affiliations:	(A): University of south carolina

The Arabidopsis FRO2 gene encodes the iron-deficiency inducible ferric chelate reductase responsible for reduction of iron at the root surface; subsequent transport of iron across the plasma membrane is carried out by a ferrous iron transporter (IRT1). We have identified seven additional FRO family members in the Arabidopsis genome. We used real time RT-PCR, northern analysis and FRO promoter-GUS fusions to examine the expression of each FRO gene in different tissues, in response to iron and copper limitation and in response to light/dark treatment. FRO2 and FRO5 are primarily expressed in roots while FRO8 is primarily expressed in shoots. FRO6 and FRO7 show high expression in all the green parts of the plant and are predicted to localize to the chloroplast. FRO1 and FRO4 are expressed at relatively low levels in siliques. FRO3 is expressed at high levels in roots and shoots. We show that like FRO2, FRO3 and FRO5 expression in roots is induced in response to iron-deficiency, while FRO3 and FRO7 expression is induced by iron-deficiency in shoots. Interestingly, when plants are Cu-deficient, the expression of FRO6 and FRO7 in shoot tissues is reduced. FRO5 shows induction in response to Cu-deficiency. Expression of FRO2, FRO3, FRO6, FRO7 and FRO8 is elevated in light-treated plants as compared to dark-treated plants. To further define the functions of each FRO, we have identified knockout lines corresponding to 7 of the 8 FRO genes. Preliminary analysis of FRO loss of function lines combined with FRO expression patterns suggests that FROs function in iron homeostasis throughout the plant.