【作者】 王晓蕾；

【导师】 李召虎； 尹延海；

【作者基本信息】 中国农业大学 ， 作物生理学， 2014， 博士

【摘要】 油菜素甾醇类化合物BRs是调节植物生长发育的重要植物激素。BR信号由膜受体BRI1接受,BRI1与其它信号组分共同调节BES1/BZR1家族的转录因子,从而控制BR响应基因的表达。转录因子BES1/BZR1可以绑定参与各调控通路的转录因子或组蛋白修饰酶来共同调节下游基因,对各个生物进程精细调控。最新研究发现BES1与转录延长因子IWS1互作,参与BR靶基因的调节,而IWS1在酵母系统中与组蛋白H3K36甲基化转移酶SDG8结合调控基因转录。本论文针对拟南芥SDG8对BR响应基因的表达调控机理进行了初步研究,阐明了SDG8参与BR信号转导通路的作用机制。首先获得SDG8基因的T-DNA插入纯合突变体材料SALK₀36941,命名为sdg8。表型观察显示,SDG8基因突变严重抑制植物的正常发育。突变体sdg8整个生育期株型矮小,并对BR处理不敏感。其次对SDG8蛋白功能进行分析并研究了SDG8与BR通路重要转录因子BES1及转录延长因子IWS1的相互作用关系,结果证实SDG8与BES1两蛋白在体内和体外均有相互作用,并且SDG8与IWS1也存在互作关系。本论文又通过转录组测序技术分析SDG8对BR响应基因表达的调控模式。全局基因表达结果显示SDG8对BR响应基因的表达起重要作用,并具有激活和抑制BR响应基因的双重作用。基因功能分析结果显示其所调节的BR响应基因的功能涉及到细胞代谢的多个方面,参与调节BR介导的细胞伸长相关基因的表达。最后用染色质免疫共沉淀技术分析了突变体sdg8中BR调节基因的H3K36三甲基化水平变化,发现所测定基因的H3K36三甲基化水平大大降低,说明组蛋白甲基化可能参与SDG8所介导的BR响应基因的表达。综上所示,本论文提出了拟南芥SDG8通过与BES1和IWSl互作参与BR信号转导并调控BR响应基因的作用模型,初步揭示了组蛋白修饰介导BR信号转导下游调控的机制,对深入阐述激素调控的作用机理有重要理论意义。更多还原

【Abstract】 Brassinosteroids (BRs) is a group of polyhydroxylated plant steroid hormones, which is involved in many aspects of plant growth and developmental processes. BRs signal through the receptor BRI1localized to the plasma membrane and other signaling components to regulate the BES1/BZR1family of transcription factors, which modulates the expression of many genes. BES1/BZR1and their interacting proteins regulate the large number of genes. Recent study reported that transcription elongater IWS1interacts with BES1and invloves in BR signal transdcuction. In yeast system, IWS1and histone3lysine36methyltransferase SDG8inform a complax to regulate the transcription of genes. In this study, we investigate the function of Arabidopsis SDG8in BR signaling and the potential mechanisms of its action.First, SDG8T-DNA knockout mutant line was gained, named sdg8. The sdg8plants display reduced-growth dwarf phenotype with compromised BR responses.Then, based on the function analysis of SDG8, we detected the interaction of SDG8between BES1and IWS1. These studies show that SDG8interacts with the transcription factor BES1in vivo and in vitro. In the same way, we found that SDG8interacts with the transcription elongation regulator IWS1.And then, we performed the RNA-seq experiment to study the regulation pattern of SDG8on BR-response genes expression. Global gene expression studies demonstrated that SDG8plays a major role in BR-regulated gene expression. SDG8functions on inducing and repressing the BR-response genes. Gene function analysis results display that SDG8-regulated genes involve in many aspects of cell progresses including BR-involved cell elongation related genes expression.Last, Chromatin Immunoprecipitation (ChIP) experiment showed that H3K36me3is reduced in BR-regulated genes in the sdg8mutant. This study suggests histone lysine methylation can involve in the regulation of BR-responsed gene expression.Based on these results, we propose that SDG8involves BR signal pathway through the interacion with BES1and IWS1; SDG8plays an essential role in mediating BR-regulated gene expression. In this study, a major mechanism by which histone modifications dictate hormonal regulation of gene expression is revealed. It’s important for the exploration of the hormone regulation mechanism.更多还原