Poster: Transcription Regulation
Abs #
1055: Participation of phosphorylation of sigma factors in regulation of gene expression in Arabidopsis plastids
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Presenter: |
Kato, Hideki , pct-4@sfns.u-shizuoka-ken.ac.jp |
Authors | Kato, Hideki (A) Shimizu, Masanori (A) Yoshimoto, Kohki (A) Kobayashi, Hirokazu (A) | | Affiliations: |
(A): Lab. Plant Cell Tech., Grad. Sch. Nutr. Envir. Sci., Univ. Shizuoka
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In green or non-green tissues, the gene expression in plastids is regulated at the multiple steps: DNA replication, transcription, post-transcriptional events, translation, and post-translational mechanisms. Transcriptional regulation is the most important among them for the gene expression in some cases. Transcription in the plastid is mediated by two distinct species of RNA polymerase and controlled in response to environmental signals. One is called PEP (plastid-encoded RNA polymerase)@which mainly transcribes photosynthesis genes, and another is known as NEP (nuclear-encoded plastid RNA polymerase) which mostly transcribes housekeeping genes. Recognition of promoters and initiation of transcription by PEP require sigma factors, which are encoded in the nuclear genome. Genes for 6 sigma factors (SIG1 to SIG6) have been identified in Arabidopsis. However, it is an intriguing question whether gene expression in the plastid is regulated only by quantitative change of sigma factors. The sites to be phosphorylated with serine/threonine (Ser/Thr) protein kinase or tyrosine (Tyr) protein kinase have been predicted in their amino acid sequences. In SIG1, there are 3 putative phosphorylation sites, two Ser/Thr phosphorylation sites and one Tyr phosphorylation site. We made transgenic Arabidopsis lines with mutated SIG1 in which each or combination of above phosphorylation sites was deleted. In a mutant line of SIG1 lacking a Ser/Thr phosphorylation site, the level of rbcL transcript was higher than that in its wild-type line and the other mutant lines when they were adapted to the dark. This result suggests that SIG1 activity would be regulated through phosphorylation with Ser/Thr protein kinase.
