Abe Kiyomi, Osakabe Keishi, Nakayama Shigeki, Endo Masaki, Tagiri Akemi, Todoriki Setsuko, Ichikawa Hiroaki, Toki Seiichi
Department of Plant Biotechnology, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan.
Plant Physiol. 2005 Oct;139(2):896-908. doi: 10.1104/pp.105.065243. Epub 2005 Sep 16.
Rad51 is a homolog of the bacterial RecA recombinase, and a key factor in homologous recombination in eukaryotes. Rad51 paralogs have been identified from yeast to vertebrates. Rad51 paralogs are thought to play an important role in the assembly or stabilization of Rad51 that promotes homologous pairing and strand exchange reactions. We previously characterized two RAD51 paralogous genes in Arabidopsis (Arabidopsis thaliana) named AtRAD51C and AtXRCC3, which are homologs of human RAD51C and XRCC3, respectively, and described the interaction of their products in a yeast two-hybrid system. Recent studies showed the involvement of AtXrcc3 in DNA repair and functional role in meiosis. To determine the role of RAD51C in meiotic and mitotic recombination in higher plants, we characterized a T-DNA insertion mutant of AtRAD51C. Although the atrad51C mutant grew normally during vegetative developmental stage, the mutant produced aborted siliques, and their anthers did not contain mature pollen grains. Crossing of the mutant with wild-type plants showed defective male and female gametogeneses as evidenced by lack of seed production. Furthermore, meiosis was severely disturbed in the mutant. The atrad51C mutant also showed increased sensitivity to gamma-irradiation and cisplatin, which are known to induce double-strand DNA breaks. The efficiency of homologous recombination in somatic cells in the mutant was markedly reduced relative to that in wild-type plants.
Rad51是细菌RecA重组酶的同源物，也是真核生物中同源重组的关键因子。从酵母到脊椎动物都已鉴定出Rad51旁系同源物。Rad51旁系同源物被认为在促进同源配对和链交换反应的Rad51组装或稳定过程中发挥重要作用。我们之前鉴定了拟南芥中的两个RAD51旁系同源基因，分别命名为AtRAD51C和AtXRCC3，它们分别是人类RAD51C和XRCC3的同源物，并在酵母双杂交系统中描述了它们产物之间的相互作用。最近的研究表明AtXrcc3参与DNA修复并在减数分裂中发挥功能作用。为了确定RAD51C在高等植物减数分裂和有丝分裂重组中的作用，我们对AtRAD51C的一个T-DNA插入突变体进行了表征。虽然atrad51C突变体在营养发育阶段生长正常，但该突变体产生的角果发育不全，其花药中不含成熟花粉粒。突变体与野生型植株杂交显示出雄配子和雌配子发生缺陷，表现为不结种子。此外，该突变体的减数分裂受到严重干扰。atrad51C突变体对已知可诱导双链DNA断裂的γ射线和顺铂也表现出更高的敏感性。相对于野生型植株，该突变体体细胞中同源重组的效率显著降低。
