|Budget Amount *help
¥3,200,000 (Direct Cost : ¥3,200,000)
Fiscal Year 2000 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1999 : ¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 1998 : ¥1,600,000 (Direct Cost : ¥1,600,000)
In this study, we have carried out characterizations of a recA-like, gene Ce-rdh-1, ATM (ataxia telangiectasia mutated gene)-like gene Ce-atl-1 and Chk2 (check point gene 2)-like gene Ce-chk-2 from the nematode Caenorhabditis elegans. Ce-rdh-1 gene was essential for meiotic recombination and for repair of DNA double-strand breaks (Takanami et al., 1998, 2000). Ce-chk-2 gene encoded an essential protein kinase to form meiotic chromosome synapses. The repression of the Ce-chk-2 gene expression resulted in the abnormal and unpaired chromosomes of pachytene nuclei, the loss of meiotic recombination and the phenotype of achiasmata of diplotene and diakinesis nuclei. However, Ce-chk-2 gene was dispensable for repair process of DNA double-strand breaks (Higashitani et al., 2000). On the contrary, Ce-atl-1 gene was necessary for DNA repair process and the sensitivity to UV irradiation was increased by the repression of Ce-atl-1 gene. The repression of Ce-atl-1 gene also increased the incidence of somatic mutations, the extensive embryonic lethality, and the aneuploidy and chromosome instability during mitosis and meiosis. It indicates that Ce-atl-1 acts as a monitoring enzyme for DNA damage checkpoint control (Aoki et al., 2000).
We have also carried out characterization of the effects of high-temperature stress on the development of pollen mother cells (PMCs) and microspores in barley plant (Hordeum vulgare L). When plants were exposed to high temperature for five days at the pre-meiotic stage, PMCs and tapetum cells failed to develop. The panicles at the heading stage had a normal appearance, but no pollen grains in their abnormal anthers were observed and their seeds were virtually sterile (Sakata et al., 2000).