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On the complexity of chloroplast RNA metabolism: psaA trans-splicing can be bypassed in chlamydomonas

Published inMolecular biology and evolution, vol. 31, no. 10, p. 2697-2707
Publication date2014
Abstract

In the chloroplast, the posttranscriptional steps of gene expression are remarkably complex. RNA maturation and translation rely on a large cohort of nucleus-encoded proteins that act specifically on a single target transcript or a small set of targets. For example in the chloroplast of Chlamydomonas, trans-splicing of the two split introns of psaA requires at least 14 nucleus-encoded proteins. To investigate the functional significance of this complex trans-splicing pathway, we have introduced an intron-less copy of psaA in the chloroplast genomes of three mutants deficient in trans-splicing and of the wild type. We find that the intron-less psaA gene rescues the mutant phenotypes. The growth of strains with the intron-less psaA is indistinguishable from the wild type under the set of different experimental conditions that were investigated. Thus, the trans-splicing factors do not appear to have any other essential function and trans-splicing of psaA can be bypassed. We discuss how these observations support the hypothesis that complex RNA metabolism in the chloroplast may in part be the result of a nonadaptive evolutionary ratchet. Genetic drift may lead to the accumulation of chloroplast mutations and the recruitment of compensatory nuclear suppressors from large preexisting pools of genes encoding RNA-binding proteins.

Keywords
  • chloroplast
  • RNA processing
  • splicing constructive neutral evolution
  • Chlamydomonas
  • synthetic biology
Funding
Citation (ISO format)
LEGENDRE LEFEBVRE, Linnka et al. On the complexity of chloroplast RNA metabolism: psaA trans-splicing can be bypassed in chlamydomonas. In: Molecular biology and evolution, 2014, vol. 31, n° 10, p. 2697–2707. doi: 10.1093/molbev/msu215
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Article (Accepted version)
accessLevelRestricted
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ISSN of the journal0737-4038
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