TEM image of O. tauri strain RCC4221. Credit: Martin Hohmann-Marriott, Herve-Moreau. Click to enlarge.

Adecade after the complete representative genomes of three Ostreococcus picoplankton groups were sequenced, researchers have sequenced and analyzed the genomes of 13 members of a natural Ostreococcus population. The analysis revealed that the O. tauri population is larger than anticipated, with high genetic and phenotypic diversity that is influenced by the algae’s natural resistance to ocean viruses.

Ostreococcus is considered a model species to study marine picophytoplankton. Though microscopic, Ostreococcus and other picoplankton are significant primary producers in the oceans and contribute to the global carbon cycle. Understanding the genetic variability of various Ostreococcus strains will help researchers understand how environmental changes affect their abundance and ability to photosynthesize.

By their name, picophytoplankton such as Ostreococcus are invisible to the naked eye. Despite their size, their global abundance means they are a widespread primary producer and form the bases of several marine food webs; in coastal areas, they account for as much as 80 percent of the available biomass.

A decade ago, the U.S. Department of Energy Joint Genome Institute (DOE JGI), a DOE Office of Science user facility, sequenced one of the Ostreococcus strains. That genome, along with other genome sequences from 3 groups of the Ostreococcus, revealed the tiny algae’s diversity and adaptation to different ecological niches around the world.

Now, a team led by researchers at the Oceanological Observatory of Banyuls, France, and including scientists at the DOE JGI, has resequenced and analyzed 13 members of a natural population of Ostreococcus tauri from the northwest Mediterranean Sea. The analysis offers a complete picture on the surprisingly large population and correspondingly high genetic and phenotypic diversity within O. tauri species.

The team identified two large candidate mating type loci, consistent with the pervasive evidence of recombination and thus sexual reproduction within the population. The work reported in Science Advances was enabled in part by the DOE JGI’s Community Science Program (CSP).

This work was also supported by the European Community’s 7th Framework program FP7 and the Agence Nationale de la Recherche.

—Article supplied by Joint Genome Institute