title: Abscisic acid affects transcription of chloroplast genes via protein phosphatase 2C-dependent activation of nuclear genes: repression by guanosine-3'-5'-bisdiphosphate and activation by sigma factor 5.
abstract: Abscisic acid (ABA) represses the transcriptional activity of chloroplast genes (determined by run-on assays), with the exception of psbD and a few other genes in wild-type Arabidopsis seedlings and mature rosette leaves. Abscisic acid does not influence chloroplast transcription in the mutant lines abi1-1 and abi2-1 with constitutive protein phosphatase 2C (PP2C) activity, suggesting that ABA affects chloroplast gene activity by binding to the pyrabactin resistance (PYR)/PYR1-like or regulatory component of ABA receptor protein family (PYR/PYL/RCAR) and signaling via PP2Cs and sucrose non-fermenting protein-related kinases 2 (SnRK2s). Further we show by quantitative PCR that ABA enhances the transcript levels of RSH2, RSH3, PTF1 and SIG5. RelA/SpoT homolog 2 (RSH2) and RSH3 are known to synthesize guanosine-3'-5'-bisdiphosphate (ppGpp), an inhibitor of the plastid-gene-encoded chloroplast RNA polymerase. We propose, therefore, that ABA leads to an inhibition of chloroplast gene expression via stimulation of ppGpp synthesis. On the other hand, sigma factor 5 (SIG5) and plastid transcription factor 1 (PTF1) are known to be necessary for the transcription of psbD from a specific light- and stress-induced promoter (the blue light responsive promoter, BLRP). We demonstrate that ABA activates the psbD gene by stimulation of transcription initiation at BLRP. Taken together, our data suggest that ABA affects the transcription of chloroplast genes by a PP2C-dependent activation of nuclear genes encoding proteins involved in chloroplast transcription.
authors.affiliation: Institute of Biology-Genetics, Faculty of Life Sciences, Humboldt University, Chausseestrasse 117, 10115, Berlin, Germany.
authors.forename: Maria V
authors.initials: MV
authors.lastname: Yamburenko
authors.affiliation: Institute of Biology-Genetics, Faculty of Life Sciences, Humboldt University, Chausseestrasse 117, 10115, Berlin, Germany.
authors.forename: Yan O
authors.initials: YO
authors.lastname: Zubo
authors.affiliation: Institute of Biology-Genetics, Faculty of Life Sciences, Humboldt University, Chausseestrasse 117, 10115, Berlin, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Börner
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism* / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D055864:Droughts; D018506:Gene Expression Regulation, Plant; D061125:Genes, Chloroplast; D006153:Guanosine Diphosphate / Q000378:metabolism; D006159:Guanosine Tetraphosphate / Q000378:metabolism*; D009154:Mutation; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism; D000071636:Protein Phosphatase 2C; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C508767:PEPPER protein, Arabidopsis; D045332:Photosystem II Protein Complex; C479885:PsbD protein, Arabidopsis; D016601:RNA-Binding Proteins; C406740:RSH2 protein, Arabidopsis; C486979:Sig5 protein, Arabidopsis; D012808:Sigma Factor; D006153:Guanosine Diphosphate; D006159:Guanosine Tetraphosphate; D000040:Abscisic Acid; C087434:ABI1 protein, Arabidopsis; C106443:ABI2 protein, Arabidopsis; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C
keywords: ABA receptor; Abscisic acid (ABA); Arabidopsis thaliana; SIG5; chloroplast transcription; mitochondrial transcription; photosynthesis; ppGpp; psbD; stress