Genome size differentiates co-occurring populations of the planktonic diatom Ditylum brightwellii(Bacillariophyta)

BMC Evolutionary Biology

Research Article

Peter von Dassow¹  E Virginia Armbrust²  Julie A Koester²  Jarred E Swalwell² 

[1] CNRS, UMR7144, Evolution du Plancton et PaleoOceans, Station Biologique de Roscoff, BP 74, 29682, Roscoff, France;School of Oceanography, University of Washington, Box 357940, 98195-7940, Seattle, WA, USA;

关键词: Internal Transcribe Spacer;    Genome Size;    Informative Site;    Genome Duplication Event;    Genome Size Variation;   

DOI  :  10.1186/1471-2148-10-1

 received in 2009-08-05, accepted in 2010-01-02,  发布年份 2010

来源: Springer

【 摘 要 】

BackgroundDiatoms are one of the most species-rich groups of eukaryotic microbes known. Diatoms are also the only group of eukaryotic micro-algae with a diplontic life history, suggesting that the ancestral diatom switched to a life history dominated by a duplicated genome. A key mechanism of speciation among diatoms could be a propensity for additional stable genome duplications. Across eukaryotic taxa, genome size is directly correlated to cell size and inversely correlated to physiological rates. Differences in relative genome size, cell size, and acclimated growth rates were analyzed in isolates of the diatom Ditylum brightwellii. Ditylum brightwellii consists of two main populations with identical 18s rDNA sequences; one population is distributed globally at temperate latitudes and the second appears to be localized to the Pacific Northwest coast of the USA. These two populations co-occur within the Puget Sound estuary of WA, USA, although their peak abundances differ depending on local conditions.ResultsAll isolates from the more regionally-localized population (population 2) possessed 1.94 ± 0.74 times the amount of DNA, grew more slowly, and were generally larger than isolates from the more globally distributed population (population 1). The ITS1 sequences, cell sizes, and genome sizes of isolates from New Zealand were the same as population 1 isolates from Puget Sound, but their growth rates were within the range of the slower-growing population 2 isolates. Importantly, the observed genome size difference between isolates from the two populations was stable regardless of time in culture or the changes in cell size that accompany the diatom life history.ConclusionsThe observed two-fold difference in genome size between the D. brightwellii populations suggests that whole genome duplication occurred within cells of population 1 ultimately giving rise to population 2 cells. The apparent regional localization of population 2 is consistent with a recent divergence between the populations, which are likely cryptic species. Genome size variation is known to occur in other diatom genera; we hypothesize that genome duplication may be an active and important mechanism of genetic and physiological diversification and speciation in diatoms.

【 授权许可】

Unknown   
© Koester et al; licensee BioMed Central Ltd. 2010. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.