Molecular analysis of control mechanisms for meiosis.

在这项研究中，我们对秀丽隐杆线虫的reca样基因Ce-rdh-1、ATM（失调性毛细血管扩张突变基因）样基因Ce-atl-1和Chk2（检查点基因2）样基因Ce-chk-2进行了表征。Ce-rdh-1基因对于减数分裂重组和DNA双链断裂的修复至关重要（Takanami et al., 1998,2000）。Ce-chk-2基因编码形成减数分裂染色体突触所必需的蛋白激酶。Ce-chk-2基因表达的抑制导致粗线核染色体异常和不配对，减数分裂重组丧失，二倍体核和裂核出现不一致表型。然而，Ce-chk-2基因在DNA双链断裂的修复过程中是不可缺少的（Higashitani et al., 2000）。相反，Ce-atl-1基因在DNA修复过程中是必需的，并且通过抑制Ce-atl-1基因增加了对紫外线照射的敏感性。Ce-atl-1基因的抑制也增加了有丝分裂和减数分裂过程中体细胞突变的发生率、广泛的胚胎致死率以及非整倍体和染色体不稳定性。这表明Ce-atl-1作为DNA损伤检查点控制的监测酶（Aoki等，2000）。我们还研究了高温胁迫对大麦花粉母细胞和小孢子发育的影响。当植物在减数分裂前期高温下暴露5 d时，pmc和绒毡层细胞不能发育。抽穗期的穗状花序外观正常，但在其异常花药中没有观察到花粉粒，其种子实际上是不育的（Sakata et al., 2000）。

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).