植物细胞的多能性和高度可塑性在芽从头发生过程中充分体现。在组织培养中，具有多能性的愈伤组织能够在激素刺激下实现不定芽的从头发生，继而发育成为完整植株。本项申请集中在芽从头发生的表观遗传调控机制。我们利用芽从头发生体系对模式植物拟南芥的表观因子突变体进行了表型筛选，发现了多个芽从头发生缺陷的表观遗传突变体，包括ATP依赖型染色质重塑因子ISWI和PKL以及组蛋白H2A泛素化E3酶AtRING1a和AtRING1b。初步研究基础还显示，这些表观遗传突变体可能作用在两条遗传通路上：1）愈伤组织多能性的获得；2）芽特征基因的激活。基于这些前期研究基础，我们将从分子遗传角度解析这些表观因子的下游基因；利用生化方法解析这些表观因子的互作蛋白和特异性来源；并分析表观因子对下游基因座位上染色质结构改变的功能。我们期望全面和系统的解析芽从头发生的表观遗传调控机制，为植物细胞可塑性和多能性提供理论依据。

The ability of plant de novo shoot organogenesis reflects the plasticity of plant cells and their pluripotency. In tissue culture, adventitious shoots could be regenerated from a pluripotent cell mass, called callus, under the control of phytohormones. Here we focus on the research of the epigenetic regulation in de novo shoot organogenesis from callus. To start this research, we screened for mutants of epigenetic factors using the de novo shoot organogenesis system and identified several mutants that were defective in shooting. Mutations in the ISWI and PKL chromatin remodeling factors and the H2A ubiquitin E3 ligase AtRING1a and AtRING1b showed a very typical shooting defect. Our primary data showed that these epigenetic factors may function in either establishment of pluripotency in callus or promotion of shoot apical genes during de novo shoot organogenesis. Based on these preliminary research data, our research will continue to focus on 1) studying the downstream targets of epigenetic factors in shooting using the molecular genetic methods; 2) characterization of their interacting proteins and their functional specificity using biochemical approaches; and 3) analyzing their roles in changing the chromatin status at their target loci. We anticipate that these studies will provide an overall view on how epigenetic mechanism is involved in de novo shoot organogenesis and will also add evidence on how plant cells are highly plastic and pluripotent.