A hallmark of meiosis in many organisms is that homologous chromosomes undergo recombination and synapsis, leading to their proper segregation during the first meiotic nuclear division. We are interested in understanding the coupling mechanisms between DNA recombination, chromosome synapsis and cell cycle regulatory networks in meiosis. These processes are fundamental to biology and medicine, and have important implications for infertility, inherited diseases, aging, and evolution.
Our primary model system is the budding yeast S. cerevisiae. The Spo11-induced DSBs are repaired robustly by error-free homologous recombination to ensure accurate segregation of homologous chromosomes and genome stability. The resulting gametes or ascospores contain an integral set of chromosomes (i.e., euploidy). We have used yeast genetic, biochemical, and cell biological tools to show that the small ubiquitin like modifier (SUMO) plays critical roles in coupling interhomolog recombination, chromosome synapsis and cell cyle checkpoint networks in meiosis.
The second model system is the Hypocrea jecorina (anamorph: Trichoderma reesei), an industrial workhorse fungus for biomass degradation. H. jecorina sexual reproduction yields hexadecad asci with four or eight inviable ascospores and an equal number of viable segmentally aneuploid ascospores. The segmentally aneuploid ascospores are induced via Ku-mediated telomere addition to modify the genome, thus increasing the diversity of genotypes and ensuring more efficient biomass degradation. The segmentally aneuploid ascospores have better adaptive advantages in the natural environments. Our findings raise issues regarding additional impacts of meiosis in promoting genetic heterogeneity and genome plasticity.