Poster: Photosynthesis

Abs # 361: A Receptor-Like Kinase Which Switches on the Expression of Photosynthesis Genes in Dedifferentiated Cells of Arabidopsis

Presenter:	Goto, Shingo , p1304@mail.f.u-shizuoka-ken.ac.jp
Authors	Goto, Shingo  (A)   Niwa, Yasuo  (A)   Kobayashi, Hirokazu  (A)
Affiliations:	(A): Graduate School of Nutritional and Environmental Sciences University of Shizuoka

The green organs such as leaves and stems of plants have photosynthetically active plastids (chloroplasts), but roots and calli do not. Signals activating transcription are transduced organ-specifically resulting in expression of photosynthesis genes in leaves, where the underlying mechanisms are not well understood. We, therefore, initiated the work to elucidate the signal transduction pathways for photosynthesis gene expression with selection of mutants which expressed the genes in calli. We applied activation tagging to an Arabidopsis line transformed with hygromycin B hopsphotransferase gene under the control of RBCS-3B promoter, and selected ces (callus expression of RBCS) mutants. The calli of ces101 were green, where transcripts for RBCS were approximately 700 times higher than those in its parental line, and gene for SIG1 encoding a _igma_factor responsible for transcription of chloroplast photosynthesis genes was also higher. One copy of T-DNA in the genome has been revealed to be inserted into a locus harbored in the P1 clone MSL1 in chromosome 3. There were 3 ORFs surrounding the inserted T-DNA, for ethylene-responsive-protein, Ser/Thr kinase (receptor-like kinase), and kinesin. The level of transcript for the receptor-like kinase was higher in calli of ces101 than that in the parental line. When the receptor-like kinase gene was driven by enhancer sequences of CaMV 35S in the parental line, they exhibited the same phenotype as ces101 line, leading to the conclusion that the CES101 is the receptor-like kinase. The CES101 gene was markedly expressed in leaves but not in roots in the wild-type line. These results suggest that CES101 gene positively regulates transcription of photosynthesis genes.