Abstract
CYP735A1 and CYP735A2 catalyze the hydroxylation of isopentenyladenine-type cytokinins (CKs) to trans-Zeatin (tZ)-type CKs. To clarify the physiological roles of the CK hydroxylation, we analyzed insertional mutants and overexpressor of the CK hydroxylase genes. cyp735a1 and cyp735a2 did not show any visible phenotype but double mutant, cyp735a1cyp735a2, displayed phenotypes only in the aerial part such as reduced size and increased rosette branches. In cyp735a1cyp735a2, amount of tZ-type CKs was lower than 3 % of that in WT and amount of iP-type CKs was twice of that in WT. Partial complementation of the mutant phenotypes by the application of tZ indicated that mutant phenotype was caused by the decreased amount of tZ-type CKs. Transgenic overexpressors of the hydroxylase genes had increased amount of tZ-type CKs but displayed no visible phenotype. We will also show the results from gene expression analysis of the double mutant using DNA microarray chips.
