We are interested in fundamental aspects of chromosome structure and functions, particularly in investigating the biochemical mechanisms underlying DNA damage response mechanisms, maintenance of genome stability and generation of genetic diversity in meiosis. These processes are fundamental to genetics and have important implications for aging, infertility, inherited diseases, evolution.
Our favorite model systems are budding yeast Saccharomyces cerevisiae meiosis and Hypocrea jecorina sexual development. Hypocrea jecorina is the telomorph of Trichoderma reesei, an industrially important cellulolytic filamentous fungus. During budding yeast meiosis, homologous DNA recombination initiates pairing and synapsis (i.e., formation of synaptonemal complex, SC) between homologous chromosomes to ensure proper chromosome segregation at the first meiotic division. Defects in meiotic DNA recombination or SC assembly often result in cell cycle arrest at meiotic prophase. We aim to understand the biochemical mechanisms of homologous recombination, SC assembly, chromosome segregation, and their controls (e.g., DNA damage and synapsis checkpoints), and their relationships with the meiotic cell cycle program. Hypocrea jecorina undergoes a heterothallic reproductive cycle, and the mating yields fertilized perithecia imbedded in fruiting bodies containing dechexad asci with 16 linearly arranged ascospores. We aim to elucidate the mechanisms of Hypocrea jecorina sporulation and meiosis.
Figure 1. Yeast Saccharomyces cerevisiae meiosis-specific chromosomal protein Red1 binds SUMO (small ubiquitin like modifer) chains to mediate assembly of synaptonemal complex (SC). Representative images of surface nuclei spreads for yeast meiotic cells stained with DAPI (blue), anti-Zip1 antibody (green), anti-V5 antibody (for V5-tagged Red1 protein; red). Zip1 is the major structural component of SC. The red1I758R mutant cell was defective is SC assembly, because its Red1 proteins could not associate with SUMO chains. (Cheng, C.-H., et al. 2006; Lin, F.-M. et al. 2009).
Figure 2. Yeast vacuole is in contact with the nuclear envelope (NE) via nucleus-vacuole junctions (NVJs) during meiosis. (A) An amphiphilic fluorescent dye, FM 4-64, was applied to visualize vacuolar membranes in live meiotic cells that expressed Zip1-GFP, Nvj1-GFP and Nup49-tdm2. Nvj1 is a nuclear inner membrane, that interacts with the vacuolar membrane protein Vac8 to promote formation of nucleus-vacuole junctions. Nup49 is a component of nuclear pore complex. Zip1 was used here a meiotic prophase marker. (B) The Nvj1-GFP patches underwent scission during two round of meiotic nuclear divisions. Time-lapse live cell imaging of Nvj1-GFP and Nup49-tdm2 from mid-prophase to the second meiotic nuclear division (MII).
Figure 3. Blue light acts as a double-edged sword in regulating sexual development of Trichoderma reesei, an industrially important cellulolytic filamentous fungus. The mating assay. Two haploid cultures were inoculated on a MEA plate. If sexual development occurs, stromata will be found at the interaction zone (marked by white arrow). Sexual development of wild-type, the Δblr1,2 double mutant and the Δenv1 diploid mutants under constant light illumination or constant darkness. The BLR1 and BLR2 proteins are blue-light receptors, ENVOY (ENV1) is a negative regulator that functions to tolerate continuous exposure to light and dampens the capacity of the fungus to perceive changes in light intensity.
Highlighted online by "The Mycelium Connection" http://myceliumconnection.blogspot.fi/2012/09/mood-lighting-for-hypocrea-jecorina.html
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