the complete plastid genomes of the two ‘dinotoms’ durinskia baltica and kryptoperidinium foliaceum完整的质体基因组的两个u201cdinotomsu201ddurinskia baltica和kryptoperidinium foliaceum.pdf

The Complete Plastid Genomes of the Two ‘Dinotoms’ Durinskia baltica and Kryptoperidinium foliaceum . . Behzad Imanian , Jean-Franc¸ois Pombert , Patrick J. Keeling* Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada Abstract Background: In one small group of dinoflagellates, photosynthesis is carried out by a tertiary endosymbiont derived from a diatom, giving rise to a complex cell that we collectively refer to as a ‘dinotom’. The endosymbiont is separated from its host by a single membrane and retains plastids, mitochondria, a large nucleus, and many other eukaryotic organelles and structures, a level of complexity suggesting an early stage of integration. Although the evolution of these endosymbionts has attracted considerable interest, the plastid genome has not been examined in detail, and indeed no tertiary plastid genome has yet been sequenced. Methodology/Principal Findings: Here we describe the complete plastid genomes of two closely related dinotoms, Durinskia baltica and Kryptoperidinium foliaceum. The D. baltica (116470 bp) and K. foliaceum (140426 bp) plastid genomes map as circular molecules featuring two large inverted repeats that separate distinct single copy regions. The organization and gene content of the D. baltica plastid closely resemble those of the pennate diatom Phaeodactylum tricornutum. The K. foliaceum plastid genome is much larger, has undergone more reorganization, and encodes a putative tyrosine recombinase (tyrC) also found in the plastid genome of the heterokont Heterosigma akashiwo, and two putative serine recombinases (serC1 and serC2) homologous to recombinases encoded by plasmids pCf1 and