An alfalfa gene similar to glutathione S-transferase is induced in root by iron deficiency

In order to isolate genes influenced by the iron (Fe) status of plants, we constructed a cDNA library from the roots of Fe-starved alfalfa (Medicago sativa L.) plants. The library was then screened with a subtracted probe. Based on the results of hybridization, we selected a full-length clone cDNA, designated as Isr1 (iron starvation-responsive gene 1). The Isr1 consisted of 815 nucleotides containing an open reading frame of 642 bp and encoded a protein with 214 amino acids, which showed a homology to glutathione S-transferase (GST, EC 2.5.1.18). A significant increase in the amount of Isr1 mRNA was observed in roots after 8 h of Fe starvation. The amount of Isr1 transcript, however, decreased rapidly on the second day, then increased again after the third day. The amount of Isr1 transcript was not influenced by the resumption of the Fe for 1 d. Possible functions of the gene product are discussed.