Abstract
Availability of inorganic nitrogen has crucial effects on growth and development of plants. Phytohormones act as mediators of changes in the internal and external environments of plant body. Cytokinin has been considered to have a function to communicate the nitrogen availability because correlation between the level of cytokinins and the nitrogen status has been reported in various plant species.
Adenylate isopentenyltransferase (IPT) is thought to catalyze the limiting step of cytokinin biosynthesis. To gain some insights into the nitrogen-responsive change of cytokinin level, we analyzed the expression pattern of these genes (AtIPT1, AtIPT3-8) in Arabidopsis by real-time PCR. In the seven genes, the accumulation of AtIPT3 mRNA was coordinated with that of cytokinin during recovery from nitrogen starvation. Since the expression of GFP gene fused to the promoter of AtIPT3 gene showed similar pattern, the nitrogen-responsive accumulation is regulated at least in parts by transcriptional level.