Abstract
In previous study, we reported that one of the isopentenyltransferase in Arabidopsis, AtIPT3, is a key determinant of nitrogen-dependent cytokinin biosynthesis. AtIPT3 is an enzyme that catalyzes the initial step in the biosynthesis of cytokinin, and the gene expression is induced by nitrate. In rice, seven genes of isopentenyltransgerase (OsIPT1-5, 7-8) were identified as the genes involved in the cytokinin biosynthesis. The intracellular localization of each gene products is observed in chloroplast, mitochondrion, or cytosol, respectively. To identify the key determinant of nitrogen-dependent cytokinin biosynthesis in rice, we analyzed gene expression of OsIPT in the nitrogen-treated rice root and shoot. In the results, we found that some OsIPT genes are induced in root and/or shoot both by nitrate and ammonium ion. It is different from the result of AtIPT3, which is induced only by nitrate. It suggests that there are different mechanisms of nitrogen-induction from OsIPTs and AtIPT3.
