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Regulation of plastid transcription by sigma factors and anti-sense RNAs in Arabidopsis thaliana.

Abstract : Chloroplasts, responsible for photosynthesis in autotrophic organisms, have a genome containing 100-130 genes, 80 of which code for proteins mainly involved in photosynthesis, transcription and translation. Gene expression, involves two types of RNA polymerases, NEP (Nucleus Encoded RNA Polymerase) and PEP (Plastid Encoded RNA Polymerase). Six nucleus encoded sigma factors participate to PEP promoter specificity. We first have analyzed the role of sigma factors in the transcriptional regulation of the two atp operons, atpI/H/F/A and atpB/E, with special emphasis on the specific contribution of SIG3 to atpH gene expression. We identified the promoters responsible for polycistronictranscripts and the internal promoters upstream of the atpH and the atpE genes. All genes of both atp operons are SIG3 and SIG2 dependent except atpI that is regulated by SIG2 only. The monocistronic -418 initiated atpH mRNA might contribute to the higher stoichiometry of atpH. A systematic analysis of plastid gene expression under different light conditions showed that SIG3 plays an important role in the transcript accumulation of atpH in high light (1300 μE) in mature plants. Similarly, SIG3 also recognizes specifically the promoter of psbN located between psbT and psbH but on the opposite DNA strand and producing an anti-sense RNA to psbT. We showed that the anti-sense RNA covers the coding region, the 5‟ UTR and almost the entire 3‟ UTR of the psbT sense transcript and thus might regulate the expression of the psbT gene by interfering in the translation of psbT mRNA via duplex formation. It could also be necessary for a processing event in the 5‟ UTR of psbH.
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Contributor : Mustafa Malik Ghulam <>
Submitted on : Tuesday, March 5, 2013 - 4:58:43 PM
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Malik Ghulam Mustafa. Regulation of plastid transcription by sigma factors and anti-sense RNAs in Arabidopsis thaliana.. Molecular biology. Université Joseph-Fourier - Grenoble I, 2010. English. ⟨tel-00797125⟩

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