In a study published in Cell Reports, Dr. ZHOU Jinqiu’s team from Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science of the Chinese Academy of Sciences (CAS), revealed the construction of different single-chromosome models in fission yeast Schizosaccharomyces pombe (S. pombe).
Different species have different number of chromosomes. What determines species diversity is a central question in biology. Traditional views support that natural selection plays an essential role in speciation. The development of techniques enables de novo synthesizing of chromosomes or "creating" new species through massive chromosome engineering in unicellular budding yeast. Whether there is strong tolerance to chromosome configuration changes is a ubiquitous attribute of eukaryotic genomes, and whether a reshuffled genome affects organismal fitness and speciation remain unclear.
Fission yeast S. pombe only have three chromosomes and is a widely used unicellular model organism to study cell cycle, epigenetics and chromosome biology. The researchers in this study took conventional genetic approaches to fuse three native chromosomes accompanied by telomeres fusion and centromeres deletion. They constructed a few single-chromosome fission yeast strains, indicating that fission yeast cells can live with one single-chromosome.
These single-chromosome yeast cells have a very different chromosome structure, but similar gene expression profiles compared with those of wild-type cells. Unexpectedly, the single-chromosome cells display few phenotypic defects. Moreover, either change of chromosome number or configuration results in reproductive isolation between wild type and single-chromosome cells, or between single-chromosome cells with different genome organizations.
The researchers concluded that eukaryotic genomes are highly flexible and can tolerate dramatic chromosomal alterations, and differences in both chromosome number and configuration lead to reproductive incompatibility.
The findings of this study as well as those reported previously in budding yeast challenge the view of chromosome territory theory, and suggest that neither global nor local chromosome organization changes significantly affect gene expression. Additionally, the single-chromosome fission yeast models established in this study offer unique tools for future research in chromosome & chromatin biology and evolution.
Dr. DU Lilin’s team from National Institute of Biological Sciences and Dr. FU Chuanhai’s team from University of Science and Technology of China of CAS also participated in the study.