title: Split photosystem protein, linear-mapping topology, and growth of structural complexity in the plastid genome of Chromera velia.
abstract: The 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.
authors: Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Jan
authors: J
authors: Janouskovec
authors: Roman
authors: R
authors: Sobotka
authors: De-Hua
authors: DH
authors: Lai
authors: Pavel
authors: P
authors: Flegontov
authors: Peter
authors: P
authors: Koník
authors: Josef
authors: J
authors: Komenda
authors: Shahjahan
authors: S
authors: Ali
authors: Ondrej
authors: O
authors: Prásil
authors: Arnab
authors: A
authors: Pain
authors: Miroslav
authors: M
authors: Oborník
authors: Julius
authors: J
authors: Lukes
authors: Patrick J
authors: PJ
authors: Keeling
mesh_terms: D025181:ATP Synthetase Complexes / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D056893:Alveolata / Q000235:genetics*; D001483:Base Sequence; D002874:Chromosome Mapping; D019143:Evolution, Molecular; D020869:Gene Expression Profiling; D018503:Genome, Protozoan; D008958:Models, Molecular; D008969:Molecular Sequence Data; D005810:Multigene Family; D010788:Photosynthesis / Q000235:genetics; D045331:Photosystem I Protein Complex / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D045331:Photosystem I Protein Complex; D015800:Protozoan Proteins; D000255:Adenosine Triphosphate; D025181:ATP Synthetase Complexes
keywords: Chromera velia; linear-mapping genome; plastid genome evolution; split protein