Poster: Hormones

Abs # 591: Cellular and subcellular localization of isopentenyltransferases in Arabidopsis thaliana

Presenter:	Ueda, Nanae , unanae@postman.riken.go.jp
Authors	Ueda, Nanae  (A)   Aoki, Koh  (A)   Takei, Kentaro  (A)   Yamaya, Tomoyuki  (A)   Sakakibara, Hitoshi  (A)
Affiliations:	(A): Plant Science Center, RIKEN (The Institute of Physical and Chemical Reseach)

The primary biosynthetic reaction of cytokinin is catalyzed by isopentenyltransferase (IPT). In Arabidopsis thaliana, seven genes (AtIPT1, AtIPT3 to AtIPT8) were identified as the biosynthesis genes. Such variations in gene organization imply that the AtIPTs are functionally differentiated. To understand the physiological role of each AtIPT, the elucidation of spatial distribution of the AtIPTs is clearly important. We constructed AtIPT promoter::GFP chimeric genes and introduced them 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. We also constructed a series of chimeric genes for AtIPTs whose C-termini were fused with GFP. These genes driven by CaMV 35S promoter were introduced into Arabidopsis epidermal cells by particle bombardment. Analysis of the fluorescence of fusion proteins suggested that AtIPT1, AtIPT3 and AtIPT5 were localized in the plastids, and AtIPT7 was in the mitochondria. These results indicate that the AtIPTs are differentially regulated in terms of the spatial distribution and that the variety implies physiological differentiation of each AtIPT.