Split photosystem protein, linear-mapping topology, and growth of structural complexity in the plastid genome of chromera velia
Flegontov, Pavel N.
Keeling, Patrick J J.
KAUST DepartmentBioscience Core Lab
Biological and Environmental Sciences and Engineering (BESE) Division
Computational Bioscience Research Center (CBRC)
Pathogen Genomics Laboratory
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AbstractThe canonical photosynthetic plastid genomes consist of a single circular-mapping chromosome that encodes a highly conserved protein core, involved in photosynthesis and ATP generation. Here, we demonstrate that the plastid genome of the photosynthetic relative of apicomplexans, Chromera velia, departs from this view in several unique ways. Core photosynthesis proteins PsaA and AtpB have been broken into two fragments, which we show are independently transcribed, oligoU-tailed, translated, and assembled into functional photosystem I and ATP synthase complexes. Genome-wide transcription profiles support expression of many other highly modified proteins, including several that contain extensions amounting to hundreds of amino acids in length. Canonical gene clusters and operons have been fragmented and reshuffled into novel putative transcriptional units. Massive genomic coverage by paired-end reads, coupled with pulsed-field gel electrophoresis and polymerase chain reaction, consistently indicate that the C. velia plastid genome is linear-mapping, a unique state among all plastids. Abundant intragenomic duplication probably mediated by recombination can explain protein splits, extensions, and genome linearization and is perhaps the key driving force behind the many features that defy the conventional ways of plastid genome architecture and function. © The Author 2013.
SponsorsThis work was supported by a grant from the Canadian Institutes of Health Research to P.J.K. (MOP-42517); by the Czech Science Foundation projects P506/12/1522 and P501/12/G055 to M.O.; by the Praemium Academiae award to J.L.; by Award IC/2010/09 by the King Abdullah University of Science and Technology (KAUST) to A. P., M.O., and J.L.; and by the project Algatech (CZ.1.05/2.1.00/03.0110) to R. S., J.K., and O.P.. P.J.K. and J.L. are Fellows of the Canadian Institute for Advanced Research. P.J.K. was supported by a Fellowship from the John Simon Guggenheim Foundation.
PublisherOxford University Press (OUP)
JournalMolecular Biology and Evolution
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