Abstract
We have been studying on responses to iron deficiency stress in higher plants. We isolated an Fe-deficiency-induced cDNA, IDI7, from the roots of Fe-deficient barley. The transcript levels of IDI7 in roots strongly correlated with iron nutritional status, and induction by Fe-deficiency was restricted to roots. IDI7 encodes a 644-amino-acid protein, and has features typical of ATP-binding cassette (ABC) transporters. IDI7 is a half-type ABC transporter and has a high amino acid similarity to mammalian transporters associated with antigen processing (TAPs). A transiently expressed fusion protein of IDI7 to GFP was localized to the tonoplast in BY-2 cells. IDI7 and its ortholog in Arabidopsis, AtIDI7, are thought to comprise a new class of ABC transporters. Genomic OsIDI7 has typical IDE1 (Iron Deficiency Responsive Element 1) in its promoter. We discuss a possible role of IDI7 in Fe-deficiency tolerance in barley roots and in higher plants.
