武大生科院细胞分裂新发现登国际刊物

　　来自武汉大学生命科学学院，杂交水稻国家重点实验室的研究人员发表了题为“Replication factor C1 (RFC1) is required for double-strandbreak repair during meiotic homologous recombination inArabidopsis”的文章，发现了一种基因：AtRFC1能通过影响同源染色体和姐妹染色单体的均等分离，调控花粉遗传物质的分布，为深入阐明减数分裂中同源重组的分子机制奠定了基础。相关成果公布在植物学领域权威刊物The Plant Journal杂志上。

　　领导这一研究的是武大生科院赵洁教授，赵教授早年毕业于华中师范大学，主要研究领域为植物生殖发育生物学，以及植物性细胞操作与细胞工程，目前科研项目包括“水稻花穗原基发生和生殖器官发育中AGP基因功能的研究”等。文章的第一作者是博士生刘扬。

　　复制因子C包含1个大亚基和4个小亚基，在DNA复制、损伤修复和细胞增殖中起重要作用，其中拟南芥复制因子C亚基1(AtRFC1)是人类复制因子C大亚基p140的同源蛋白，对这一基因的研究将有助于解析细胞的一些重要进程。

　　在这篇文章中，研究人员发现AtRFC1基因能通过影响花粉和胚囊发育控制拟南芥角果的育性，并且也指出AtRFC1能通过影响同源染色体和姐妹染色单体的均等分离控制花粉遗传物质的分布，从而参与花粉母细胞减数分裂的过程。

　　而且在减数分裂的同源重组中，AtRFC1基因主要参与DNA双链断裂的修复，在AtSPO11-1基因的下游通路中发挥作用，此外这一基因还可能参与了AtRAD51介导的同源重组修复，从而揭示了AtRFC1基因参与植物DNA修复的机理，这一研究为深入阐明减数分裂中同源重组的分子机制奠定了基础。

　　另外近期这一研究组还发表了另外一项研究成果：发现拟南芥AtMT4a和AtMT4b基因的重要作用，这对于揭示种子发育和萌发中ABA和GA激素、MT基因与Zn离子供给及调控之间的关系具有重要的意义。

　　研究人员发现拟南芥AtMT4a和AtMT4b基因参与种子萌发及幼苗早期发育，RNAi转基因植株中种子重量减少、幼苗早期生长减缓，并且在胚胎晚期AtMT4a和AtMT4b特异表达。

　　研究人员也发现AtMT4a和AtMT4b蛋白主要通过与Zn金属离子结合而调节细胞内离子的贮存和分布，维持金属离子微环境的平衡，并且发现 ABA和GA可能通过调节AtMT4a和AtMT4b的表达水平、继而通过锌指转录因子和锌结合蛋白的作用，影响胚胎晚期和幼苗早期发育。这些研究对于揭示种子发育和萌发中ABA和GA激素、MT基因与Zn离子供给及调控之间的关系具有重要的意义。

　　原文摘要：

　　Replication factor C1 (RFC1) is required for double-strandbreak repair during meiotic homologous recombination inArabidopsis

　　Replication factor C1 (RFC1), which is conserved in eukaryotes, is involved in DNA replication and checkpoint control. However, a RFC1 product participating in DNA repair at meiosis has not been reported in Arabidopsis. Here, we report functional characterization of AtRFC1 through analysis of the rfc1C2 mutant. The rfc1C2 mutant displayed normal vegetative growth but showed silique sterility because the male gametophyte was arrested at the uninucleus microspore stage and the female at the functional megaspore stage. Expression of AtRFC1 was concentrated in the reproductive organ primordia, meiocytes and developing gametes. Chromosome spreads showed that pairing and synapsis were normal, and the chromosomes were broken when desynapsis began at late prophase I, and chromosome fragments remained in the subsequent stages. For this reason, homologous chromosomes and sister chromatids segregated unequally, leading to pollen sterility. Immunolocalization revealed that the AtRFC1 protein localized to the chromosomes during zygotene and pachytene in wild-type but were absent in the spo11C1 mutant. The chromosome fragmentation of rfc1C2 was suppressed by spo11C1, indicating that AtRFC1 acted downstream of AtSPO11-1. The similar chromosome behavior of rad51 rfc1C2 and rad51 suggests that AtRFC1 may act with AtRAD51 in the same pathway. In summary, AtRFC1 is required for DNA double-strand break repair during meiotic homologous recombination of Arabidopsis.