XVI International Botanical Congess

Cytokinin is a phytohormone which regulate cell and chloroplast developments in any stage of plant growth. In cultured green tobacco cells, cell growth, chlorophyll synthesis and chloroplast mRNA expressions were promoted by cytokinin stimulation for 1 week after transient cytokinin starvation for 4 days. As these chloroplast mRNAs, cab, rbcS and psbA, were not induced by cytokinin at 24-hr cytokinin stimulation, the stage of cytokinin stimulation was considered as early or primary step of cytokinin signal transduction pathway. Three cytokinin inducible gene (cig) was identified and cloned by fluorescent differential display from cultured green tobacco cells in 12-hr cytokinin stimulation. All cig expression was induced by both of natural cytokinin and synthetic cytokinins independent with light stimulation. Cloning and sequence analysis for full length cDNA of cig is in progress.