Abstract
The primary biosynthetic reaction of cytokinin is catalyzed by isopentenyltransferase (IPT). In Arabidopsis thaliana, seven genes (AtIPT1, AtIPT3 to AtIPT9) were identified as the biosynthesis genes.In the last year's meeting, we reported differential localization of AtIPTs in plastids and mitochondria. To understand physiological function of each AtIPT, we tried to determine the expression site of the AtIPTs with transgenic Arabidopsis. We constructed AtIPT promoter::GFP chimeric genes and introduced into Arabidopsis. In the transgenic plants, AtIPT1 expressed in elongation area and vascular stele of roots. AtIPT3 expressed in the companion cell of phloem over a whole seedling. AtIPT5 expressed in lateral root primodium of perycycle. AtIPT7 expressed in vascular stele and companion cell of phloem in root. These results suggest that the AtIPTs are differentially regulated in terms of the spatial distribution and that the variety implies physiological differentiation of each AtIPT.
