Euglena Light-Harvesting Complexes Are Encoded by Multifarious Polyprotein mRNAs that Evolve in Concert

Light-harvesting complexes (LHCs) are a superfamily of chlorophyll- and carotenoid-binding proteins that are responsible for the capture of light energy and its transfer to the photosynthetic reaction centers. Unlike those of most eukaryotes, the LHCs of Euglena gracilis are translated from large mR...

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Bibliographic Details
Published in:Molecular biology and evolution 2008-01, Vol.25 (1), p.92-100
Main Authors: Koziol, Adam G., Durnford, Dion G.
Format: Article
Language:English
Subjects:
Algal Proteins - genetics
Animals
Botany
Euglena gracilis
Euglena gracilis - genetics
Evolution, Molecular
Evolutionary biology
Light-Harvesting Protein Complexes - genetics
Molecular biology
Multigene Family - genetics
Proteins
Protozoan Proteins - genetics
Ribonucleic acid
RNA
RNA, Algal - genetics
RNA, Messenger - genetics
RNA, Protozoan - genetics
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Summary:Light-harvesting complexes (LHCs) are a superfamily of chlorophyll- and carotenoid-binding proteins that are responsible for the capture of light energy and its transfer to the photosynthetic reaction centers. Unlike those of most eukaryotes, the LHCs of Euglena gracilis are translated from large mRNAs, producing polyprotein precursors consisting of multiple concatenated LHC subunits that are separated by conserved decapeptide linkers. These precursors are posttranslationally targeted to the chloroplast and cleaved into individual proteins. We analyzed expressed sequence tags from Euglena to further characterize the structural features of the LHC polyprotein-coding genes and to examine the evolution of this multigene family. Of the 19 different LHC transcriptional units we detected, 17 encoded polyproteins composed of both tandem and nontandem repeats of LHC subunits; organizations that likely occurred through unequal crossing-over. Of the 2 nonpolyprotein-encoding LHC transcripts detected, 1 evolved from the truncation of a polyprotein-coding gene. Duplication of LHC polyprotein-coding genes was particularly important in the LHCI gene family where multiple paralogous sequences were detected. Intriguingly, several of the individual LHC-coding subunits both within and between transcriptional units appeared to be evolving in concert, suggesting that gene conversion has been a significant mechanism for LHC evolution in Euglena.
ISSN:0737-4038
1537-1719
DOI:10.1093/molbev/msm232