Expressions of A-type and C-type Cyclins Induced by Exogenous Cytokinin Treatment on Leaf Blades and Calli of Rice (Oryza sativa L.)

The expression patterns of cyclin genes, which play a crucial role on cell cycle control, were analyzed with rice calli and leaf blades from seedlings. When callus was transferred from media containing the combinations of 2,4-D and kinetin under the dark conditions to medium supplemented with cytokinin-only on 7 days after the cultures, the expression levels of A-, B- and C-type cyclins from callus were increased significantly. Despite the fact that cyclin genes were well expressed on leaf blades rather than other organs in rice seedlings, rice leaf blades grown on the medium containing various combinations and concentrations of cytokinin for 24 hours had no major effect on the expression patterns of cyclins except zeatin. The relation between cytokinin regulation and the expression of cyclins of rice is discussed.