拟南芥染色质重塑因子AtBRAHMA维持主根干细胞微环境的机理研究

The large multi-subunit of chromatin remodeling complexes regulates DNA accessibility for activation or repression of transcription by using its ATP hydrolysis to modulate nucleosome state. It has been reported that AtBRM,the putative subunit of chromatin remodeling complexes plays a central role in regulation of flowering time control, floral organ development and seed maturation. Nevertheless,less is known about AtBRM in the regulation of root development.Our existing data showed that brm3,the AtBRM loss-of-function mutant, displayed a shorter root phenotype and reduced QC activity, which suggested the involvement of AtBRM in root stem cell niche maintenance in Arabidopsis. In this study, we concentrated on the mechanism characterization of root stem cell niche maintenance by AtBRM, and a series resarch as the follows will be involved.1. To investigate the expression and localization of genes related to root stem cell niche maintenance in brm3 mutant.2.To investigate the AtBRM-interacting transcriptional factor (chromatin factor) through yeast two hybridization screening; 3. To investigate the direct AtBRM-interacting genes in Arabidopsis by means of ChIP-seq, especially those gene involved in root stem cell niche maintenance.Based on the research above, we try to clarify the molecular mechanism of AtBRM in root stem cell niche maintenance,and contribute to the exploration of the chromatin remodeling complexes in plant growth and development.

染色质重塑复合体通过其具有ATPases活性的亚基水解ATP释放能量，改变核小体构象而改变DNA的"可及性"，进而调控基因表达。AtBRAHMA（AtBRM，推测的染色质重塑复合体亚基），参与植物开花、花器官发育和种子成熟等多种生理过程，但至今未见AtBRM调控主根发育的报道。我们发现AtBRM缺失突变体brm3主根变短，QC（quiescent centre）干细胞活性降低，初步表明AtBRM通过维持主根干细胞微环境调控主根发育。本项目拟在此基础上，将维持主根干细胞微环境报告基因导入brm3中，确定brm3中相关基因表达量及位置变化；通过转录因子文库和染色质因子的酵母双杂交筛选，确定与AtBRM发生互作的蛋白；利用ChIP-seq技术，确定AtBRM的靶基因。以期阐明AtBRM维持主根干细胞微环境过程的分子机制，为全面解析植物染色质重塑复合体调控植物生长发育的机制奠定基础。

染色质重塑复合体通过其具有ATPase活性的亚基水解ATP释放能量，影响核小体构象（染色质重塑）而改变DNA的“可及性”（accessibility），进而影响转录因子与特定DNA区域的结合从而激活或者抑制基因表达。植物染色质重塑复合体尚未分离鉴定，关于其亚基的组成还知之甚少。但对染色质重塑复合体催化亚基BRAHMA（BRM）的研究可从侧面探究植物染色质重塑复合体的功能。我们研究发现：（1）BRM 缺失导致拟南芥主根变短，主根生长速率和主根分生组织大小较同一时期野生型小，且主根根冠干细胞微环境异常；（2）BRM突变体主根中生长素运输蛋白基因PINs表达降低，从而影响其主根生长素分布，生长素途径调控主根发育的关键因子PLT1和PLT2在AtBRM突变体主根中表达下降，且在AtBRM突变体中过表达PLT2可部分回复其短根表型；（3）BRM通过直接结合于生长素运输蛋白PINs染色质区，调节PINs的表达，影响生长素在主根中分布，从而影响PLTs的表达，进而影响主根根冠干细胞微环境的维持。以上结果为染色质重塑参与主根发育奠定了基础，对提高作物的抗旱性具有很好的启示。