Reverse transcription of spliced psbA mRNA in Chlamydomonas spp. and its possible role in evolutionary intron loss

Reverse transcription of mRNA is thought to be an important first step in a model that explains certain evolutionary changes within genes, such as the loss of introns or RNA editing sites. In this model, reverse transcription of mRNA produces cDNA molecules that replace part of the parental gene by...

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Bibliographic Details
Published in:Molecular biology and evolution 2013-12, Vol.30 (12), p.2666-2675
Main Authors: Odom, Obed W, Herrin, David L
Format: Article
Language:English
Subjects:
Algae
Base Sequence
Chlamydomonas
Chlamydomonas - classification
Chlamydomonas - genetics
Deoxyribonucleic acid
DNA
Evolution, Molecular
Genes
Genes, Chloroplast
Genetic engineering
Genetic Variation
Genome, Chloroplast
Homologous Recombination
Hybrids
Introns
Molecular Sequence Data
Molecules
Photosystem II Protein Complex - genetics
Phylogeny
Plant Proteins - genetics
Reverse Transcription
RNA Splicing
RNA, Chloroplast - metabolism
Sequence Deletion
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Summary:Reverse transcription of mRNA is thought to be an important first step in a model that explains certain evolutionary changes within genes, such as the loss of introns or RNA editing sites. In this model, reverse transcription of mRNA produces cDNA molecules that replace part of the parental gene by homologous recombination. In vivo evidence of reverse transcription of physiologically relevant mRNAs is generally lacking, however, except in genetically engineered cells. Here, we provide in vivo evidence for reverse transcription of the chloroplast psbA mRNA in two naturally occurring species of Chlamydomonas (raudensis and subcaudata) that is based on the presence of spliced cDNAs in both organisms. The psbA cDNAs, which lack the group II intron of the genomic gene, are nearly full length, and the majority of them--though not all--are in the form of RNA-cDNA hybrids. Moreover, the presence in these species of psbA cDNAs is correlated with the loss of an early group I intron from the same psbA gene. The group II intron that interrupts psbA in C. raudensis and C. subcaudata potentially encodes a protein with a reverse transcriptase domain, and the C. raudensis protein was shown to have reverse transcriptase activity in vitro. These results provide strong evidence for reverse transcription of a physiologically important mRNA (psbA) in two species of Chlamydomonas that have also lost an intron from the same gene, possibly through recombination with the cDNA.
ISSN:0737-4038
1537-1719
DOI:10.1093/molbev/mst163