Endonucleolytic activation directs dark-induced chloroplast mRNA degradation |
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| Authors: | Baginsky Sacha Gruissem Wilhelm |
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| Affiliation: | Institute of Plant Sciences, Swiss Federal Institute of Technology, ETH Zentrum, LFW E51.1, Universit?tstrasse 2, CH-8092 Zürich, Switzerland. sacha.baginsky@ipw.biol.ethz.ch |
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| Abstract: | Plastid mRNA stability is tightly regulated by external signals such as light. We have investigated the biochemical mechanism responsible for the dark-induced decrease of relative half-lives for mRNAs encoding photosynthetic proteins. Protein fractions isolated from plastids of light-grown and dark-adapted plants correctly reproduced an RNA degradation pathway in the dark that is downregulated in the light. This dark-dependent pathway is initiated by endonucleolytic cleavages in the petD mRNA precursor substrate proximal to a region that can fold into a stem–loop structure. Polynucleotide phosphorylase (PNPase) polyadenylation activity was strongly increased in the protein fraction isolated from plastids in dark-adapted plants, but interestingly PNPase activity was not required for the initiation of dark-induced mRNA degradation. A protein factor present in the protein fraction from plastids of light-grown plants could inactivate the endonuclease activity and thereby stabilize the RNA substrate in the protein fraction from plastids of dark-adapted plants. The results show that plastid mRNA stability is effectively controlled by the regulation of a specific dark-induced RNA degradation pathway. |
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