title: The nuclear-encoded sigma factor SIG4 directly activates transcription of chloroplast psbA and ycf17 genes in the unicellular red alga Cyanidioschyzon merolae.
abstract: The plant organelle chloroplast originated from the endosymbiosis of a cyanobacterial-like photosynthetic bacterium, and still retains its own genome derived from this ancestor. We have been focusing on a unicellular red alga, Cyanidioschyzon merolae, as a model photosynthetic eukaryote. In this study, we analyzed the transcriptional specificity of SIG4, which is one of four nuclear-encoded chloroplast RNA polymerase sigma factors in this alga. Accumulation of the SIG4 protein was observed in response to nitrogen depletion or high light conditions. By comparing the chloroplast transcriptomes under nitrogen depletion and SIG4-overexpressing conditions, we identified several candidate genes as SIG4 targets. Together with the results of chromatin immunoprecipitation analysis, the promoters of the psbA (encoding the D1 protein of the photosystem II reaction center) and ycf17 (encoding a protein of the early light-inducible protein family) genes were shown to be direct activation targets. The phycobilisome (PBS) CpcB protein was decreased by SIG4 overexpression, which suggests the negative involvement of SIG4 in PBS accumulation.
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1-29 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Gaku
authors.initials: G
authors.lastname: Fujii
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1-29 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Saitama 332-0012, Japan.
authors.forename: Sousuke
authors.initials: S
authors.lastname: Imamura
authors.affiliation: Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Saitama 332-0012, Japan Center for Frontier Research, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Era
authors.affiliation: Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Saitama 332-0012, Japan Center for Frontier Research, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan.
authors.forename: Shin-ya
authors.initials: SY
authors.lastname: Miyagishima
authors.affiliation: Graduate School of Horticulture, Chiba University, 648 Matsudo, Matsudo, Chiba 271-8510, Japan.
authors.forename: Mitsumasa
authors.initials: M
authors.lastname: Hanaoka
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1-29 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Saitama 332-0012, Japan kntanaka@res.titech.ac.jp.
authors.forename: Kan
authors.initials: K
authors.lastname: Tanaka
mesh_terms: D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000235:genetics; D060365:Chloroplast Proteins / Q000235:genetics*; D047369:Chromatin Immunoprecipitation; D061125:Genes, Chloroplast; D008027:Light; D046228:Microarray Analysis; D045332:Photosystem II Protein Complex / Q000235:genetics*; D045524:Phycobilisomes / Q000235:genetics; D010802:Phylogeny; D011401:Promoter Regions, Genetic; D012808:Sigma Factor / Q000737:chemistry / Q000235:genetics*; D059467:Transcriptome
chemical_list: D060365:Chloroplast Proteins; D045332:Photosystem II Protein Complex; D045524:Phycobilisomes; D012808:Sigma Factor
keywords: Cyanidioschyzon merolae; chloroplast; red algae; sigma factor; transcriptional regulation