武大生科院細胞分裂新發現登國際刊物

　　來自武漢大學生命科學學院，雜交水稻國家重點實驗室的研究人員發表了題為“Replication factor C1 (RFC1) is required for double-strandbreak repair during meiotic homologous recombination inArabidopsis”的文章，發現了一種基因：AtRFC1能通過影響同源染色體和姐妹染色單體的均等分離，調控花粉遺傳物質的分布，為深入闡明減數分裂中同源重組的分子機制奠定了基礎。相關成果公布在植物學領域權威刊物The Plant Journal雜志上。

　　領導這一研究的是武大生科院趙潔教授，趙教授早年畢業于華中師范大學，主要研究領域為植物生殖發育生物學，以及植物性細胞操作與細胞工程，目前科研項目包括“水稻花穗原基發生和生殖器官發育中AGP基因功能的研究”等。文章的第一作者是博士生劉揚。

　　復制因子C包含1個大亞基和4個小亞基，在DNA復制、損傷修復和細胞增殖中起重要作用，其中擬南芥復制因子C亞基1(AtRFC1)是人類復制因子C大亞基p140的同源蛋白，對這一基因的研究將有助于解析細胞的一些重要進程。

　　在這篇文章中，研究人員發現AtRFC1基因能通過影響花粉和胚囊發育控制擬南芥角果的育性，并且也指出AtRFC1能通過影響同源染色體和姐妹染色單體的均等分離控制花粉遺傳物質的分布，從而參與花粉母細胞減數分裂的過程。

　　而且在減數分裂的同源重組中，AtRFC1基因主要參與DNA雙鏈斷裂的修復，在AtSPO11-1基因的下游通路中發揮作用，此外這一基因還可能參與了AtRAD51介導的同源重組修復，從而揭示了AtRFC1基因參與植物DNA修復的機理，這一研究為深入闡明減數分裂中同源重組的分子機制奠定了基礎。

　　另外近期這一研究組還發表了另外一項研究成果：發現擬南芥AtMT4a和AtMT4b基因的重要作用，這對于揭示種子發育和萌發中ABA和GA激素、MT基因與Zn離子供給及調控之間的關系具有重要的意義。

　　研究人員發現擬南芥AtMT4a和AtMT4b基因參與種子萌發及幼苗早期發育，RNAi轉基因植株中種子重量減少、幼苗早期生長減緩，并且在胚胎晚期AtMT4a和AtMT4b特異表達。

　　研究人員也發現AtMT4a和AtMT4b蛋白主要通過與Zn金屬離子結合而調節細胞內離子的貯存和分布，維持金屬離子微環境的平衡，并且發現 ABA和GA可能通過調節AtMT4a和AtMT4b的表達水平、繼而通過鋅指轉錄因子和鋅結合蛋白的作用，影響胚胎晚期和幼苗早期發育。這些研究對于揭示種子發育和萌發中ABA和GA激素、MT基因與Zn離子供給及調控之間的關系具有重要的意義。

　　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.