减数分裂分子途径起始于程序化DNA双链断裂（DSB）位点的产生，其形成机制在不同物种间既呈现保守性，也具有一定程度的种属特异性。最新研究表明，在酵母和小鼠中，组蛋白修饰模式H3K4me3在DSB热点形成中起到核心调控作用，但其相关机制在植物中还不清楚。在经典的玉米减数分裂异常突变体segregation abnormality II （segII）中，DSB数量剧烈降低，同源染色体配对无法正确完成。利用图位克隆方法，我们已经将突变位点锁定在第三号染色体的一段22kb区间内；此区间只包含1个基因，与拟南芥ATX家族高度同源，编码可能的H3K4甲基化转移酶。本项目中，我们将利用多种细胞生物学手段，阐明segII突变体的染色体异常表型；结合多种分子生物学方法，验证候选基因，阐明其在减数分裂过程中的生物学功能。研究结果将为解析组蛋白甲基化对于植物减数分裂过程的表观遗传调控提供重要的研究方向。

Meiosis recombination is initiated from the programmed formation of DNA double strand breaks (DSBs). The key pathways involving meiosis exhibit both similar and distinct characters in different organisms. The latest studies in yeast and mouse have shown that the histone modification, H3K4me3, play important roles in the establishment of DSB hotspots. The related mechanism, however, is still elusive in plant until now. In the segregation abnormality II (segII), a classic meiotic mutant in maize, the number of DSBs showed dramatically reduced, and the homologous chromosomes failed to pair between each other. Using map-based cloning, we delineated the mutation site into a 22kb region on chromosome 3, where only harboring one gene, encoding a putative histone methylation transferase and belonging to Arabidopsis Trithorax family. In this research, we will further identify the meiotic phenotypes in the segII mutants utilizing the multiple cytological approaches. In addition, the candidate gene underlying the segII mutation will be verified by creating new mutant alleles. Moreover, we will attempt to elucidate the roles of the candidate gene in regulating meiosis by integrating the results from multifaceted ways. Our results will shed light on how histone modifications are involving in controlling meiosis in plant.