花粉壁作为特殊的细胞壁结构可保护花粉免受外界生物及非生物胁迫，保证植物雄性生殖细胞的发育和传递。花粉壁发育需要绒毡层和小孢子母细胞协同配合。绒毡层负责花粉壁物质合成，小孢子母细胞负责花粉壁模式建立。DNA甲基转移酶EFD可同时调控这两个过程。其在绒毡层和小孢子母细胞都有高表达，突变后导致花粉壁发育缺陷和相关基因表达下调。DNA甲基化是研究热点，但EFD调控的分子机制不清。前期研究找到EFD下游关键转录因子HB21，其表达可能受EFD的DNA甲基化抑制；HB21可直接抑制相关花粉壁基因的表达。前期工作初步建立由“EFD-HB21”介导的全新遗传通路。本项目拟采用细胞生物、分子生物和生物化学方法，探究EFD通过DNA甲基化抑制基因表达的机理；HB21抑制基因转录的机制；及该通路在陆生植物花粉/孢子发育过程中的意义。通过本项目可明晰花粉壁发育的协同调控机制，为提高植物育性和分子育种提供新的借鉴。

Pollen wall is a a particular cell wall structure surrounding pollen grains. Pollen wall can protect pollen grains from biotic and abiotic stresses, which plays crucial roles in the male germ cell development and transmission. The pollen wall development requires the coordination of tapetum and microsporocyte. Tapetum is responsible for pollen wall material synthesis, while microsporocyte is responsible for pollen wall pattern establishment. Previous study reported that the knockout of EFD, the gene encoding a DNA methyltransferase leads to both defective pollen wall and disruptive pollen wall pattern. EFD is expressed in both tapetum and microsporocyte. Several genes critical for pollen wall development are severely down regulated in efd. DNA methylation is a hot research field, but it is unclear how EFD regulates pollen wall development. The pre-project work showed that one transcriptional factor, HB21, was significantly up-regulated in tapetum and microsporocyte in the efd mutant. EFD might repress the expression of HB21 through DNA methylation. HB21 can repress the expression of the genes down-regulated in efd. Based on the pre-project work, a novel genetic regulatory pathway, “EFD-HB21-key pollen wall development genes”, was preliminary established. In this project, using the cytological, molecular biological and biochemical approaches, we attempt to explore: how EFD represses HB21 through DNA methylation; how HB21 represses the transcription of the pollen wall development genes; whether this pathway is conserved in the landing plants during pollen/spore wall development. Through this project, it will be clear that the molecular mechanism of the coordination of tapetum and microsporocyte to regulate pollen wall development, which will facilitate the knowledge of both plant fertility and molecular breeding.