Induced activity of adenine phosphoribosyltransferase (APRT) in iron-deficient barley roots: a possible role for phytosiderophore production

To isolate the genes involved in the response of graminaceous plants to Fe- deficient stress, a protein induced by Fe-deficiency treatment was isolated from barley (Hordeum vulgare L.) roots. Based on the partial amino acid se quence of this protein, a cDNA (HvAPT1) encoding adenine phosphoribosyltran sferase (APRT: EC 2.4.2.7) was cloned from a cDNA library prepared from Fe- deficient barley roots, Southern analysis suggested that there were at leas t two genes encoding APRT in barley, Fe deficiency increased HvAPT1 express ion in barley roots and resupplying Fe to the Fe-deficient plants rapidly n egated the increase in HvAPT1 mRNA. Analysis of localization of HvAPT1-sGFP fusion proteins in tobacco BY-2 cells indicated that the protein from HvAP T1 was localized in the cytoplasm of cells. Consistent with the results of Northern analysis, the enzymatic activity of APRT in barley roots was remar kably increased by Fe deficiency. This induction of APRT activity by Fe def iciency was also observed in roots of other graminaceous plants such as rye , maize, and rice. In contrast, the induction was not observed to occur in the roots of a non-graminaceous plant, tobacco. Graminaceous plants general ly synthesize the mugineic acid family phytosiderophores (MAs) in roots und er Fe-deficient conditions. In this paper, a possible role of HvAPT1 in the biosynthesis of MAs related to adenine salvage in the methionine cycle is discussed.