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

ABSTRACT: BACKGROUND:Diatoms 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. RESULTS:All 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. CONCLUSIONS:The 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.

SUBMITTER: Koester JA

PROVIDER: S-EPMC2821323 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

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

Koester Julie A JA Swalwell Jarred E JE von Dassow Peter P Armbrust E Virginia EV

BMC evolutionary biology 20100102

<h4>Background</h4>Diatoms 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 physiol ...[more]

PMID: 20044934

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Project description:This study deals with Ulnaria species found and described from two regions of China with large climate differences during the period of 2014-2022. The first region, located in the Wuling Mountains and Hunan province, has a subtropical climate and the second in Qinghai, a northwest province of China, has a highland continental climate which is characterized by a cold and long winter and warm, short summer. Previously there were nine new Ulnaria species published from the first region. This study describes 14 additional new Ulnaria taxa, nine of which were found in the first region and five of which were found in the second region. A key to the Ulnaria species that have been described from China is provided. The main morphological characteristics for 63 Ulnaria taxa are summarized in Appendices which allow the division of these Ulnaria taxa into three groups: the seven members of group one all possess both uniseriate striae and valve marginal spines, the 42 members of group two all possess uniseriate or mostly uniseriate striae but without the valve marginal spines, and the 14 members of group three all possess mostly biseriate striae and without valve marginal spines. To summarize the morphological characters of the published Ulnaria taxa and 14 taxa described in this study several conclusions for the characterization of Ulnaria are drawn: 1) each cell has two valve-appressed, long plate-like plastids; 2) living cells of many Ulnaria species often lie in girdle view on a slide because they have deep mantles and some copulae associated with either the epivalve or the hypovalve so that the cell depth is often larger than the valve width; 3) the basic structures forming a valve include sternum, virgae, and vimines/viminules; 4) the valvocopula is a closed hoop which has a similar ultrastructure in all Ulnaria taxa but differs from the other copulae in structure; 5) the configuration of girdle bands is a common condition; 6) the life history of Ulnaria can be divided into the four series of successive stages: auxospore, initial cell, pre-normal vegetative cell, and normal vegetative cell, which is very similar to the life history of Hannaeainaequidentata (Lagerstedt) Genkal and Kharitonov; 7) the closed valvocopula is proposed as a definition character for the genus Ulnaria because demonstrating all girdle bands closed is impracticable.

Dataset Information

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

Publications

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

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