NEW YORK, Feb. 20 - An international consortium of researchers has completed sequencing the genome of the yeast Schizosaccharomyces pombe.
Although the yeast S. cerevisiae, sequenced in 1997, is considered the primary model for eukaryotic research, this team believes that the S. pombe genome, the second yeast and the sixth eukaryotic organism to be fully decoded, will also prove valuable to genetic and evolutionary research.
In particular, this yeast could provide insight into the differences between eukaryotic and prokaryotic cells, between unicellular and multicellular organisms, and supply a model for eukaryotic cell cycling, mitosis and meiosis, DNA repair, and recombination.
S. pombe has some significant differences from its better-known cousin, according to the researchers, whose study appears in Wednesday's issue of the journal Nature.
The sequencing team discovered that it has substantially fewer genes than S. cerevisiae: roughly 4,800 rather than 5,600. That insight drops the lower limit for free-living single-celled eukaryotes, and also suggests that the distinction between prokaryotic and eukaryotic cell development might rest not only on gene number but also on their type and interaction.
This yeast also has markedly more introns--about 4,700 compared to S. cerevisiae's 275. Furthermore, the researchers identified hundreds of genes and 681 proteins found in S. pombe that do not appear in S. cerevisiae. Unfortunately, though, only two genes unique to S. pombe appear to have relevance to human disease, the team reports.
"S. pombe also has more proteins that appear to be involved in transporting sugars or other molecules, larger centromeres ... and an apparent lack of recent whole-genomic duplication," Jonathon Eisen, a scientist with The Institute for Genomic Research, writes in an article that appears in the same issue of Nature. These differences, he writes, could make S. pombe a better model for some cellular processes.
The project was coordinated by Bart Barrell and colleagues at the Wellcome Trust Sanger Institute in Cambridge, UK, and directed by Paul Nurse at the Cancer Research UK London Research Institute. A dozen other European research groups and a few American labs also participated in the sequencing effort.
Nurse won the 2001 Nobel Prize for his work on the cell cycle in S. pombe.
The sequence was completed at 8-fold coverage, and has been fully annotated.