花生组蛋白去乙酰化酶AhHDA1调节干旱胁迫响应的分子机制研究

Histone acetylation, mediated by histone deacetylase (HDA), is one of the most important epignetic modification to regulate the genes expression. Plant HDAs is also involved in the cell differentiation, growing development and resepose to the biology or abiotic stress in plant, but the moleuclar mechainsm in epignetic and the regulatory network of plant HDAs is still not clear. We found peanut AhHDA1 gene was up-regulated in the early response to drought stress, and the eexpression of AhAREB1 and AhNCED1 gene could be regulated by AhHDA1. AhHDA1 could rescue the phenotype of Arabidopsis homologue mutant hda6,these results indicate functional AhHDA1 gene may join in the process of the early response of drought stress by regulating the expression of drought response genes. The project wants to systematic research the expression pattern and function of AhHDA1 under drought stress in peanut, analyze whether AhHDA1 direct mediated AhAREB1 or AhNCED1 genes acetylation modification to affect the drought resistance, find the acting chromatin site in this process, and preliminary understand the signal network of the drought regualtion genes expression regulated by AhHDA1 in peanut. It is useful for us to better understand the molecular mechainsm of peanut responses to drought stress at the epigenetic level.

组蛋白去乙酰化酶（HDA）介导的核心组蛋白的乙酰化修饰是基因表达表观遗传调控的重要方式。植物中的HDAs参与细胞分化、生长发育以及对生物和非生物胁迫等内外信号应答等过程。然而对HDAs的表观遗传分子机制及其调控网络知之甚少。我们前期工作发现，花生AhHDA1基因在干旱胁迫初期明显上调，并影响干旱应答基因AhAREB1和AhNCED1的表达，AhHDA1能恢复拟南芥同源基因突变体hda6的表型。表明AhHDA1是一个功能性基因，可能通过调节干旱应答基因的表达参与花生响应干旱。本项目拟系统研究AhHDA1在花生响应干旱过程中的表达模式和调节功能；分析其是否通过组蛋白去乙酰化作用直接调控AhAREB1和AhNCED1基因的表达影响花生的抗旱性；探明其在染色质区域的分子作用位点，初步认识AhHDA1参与干旱胁迫信号途径中的基因调控网络。本研究将加深我们在表观遗传调控层面对花生响应干旱胁迫的认识。

植物HDA影响作物响应非生物胁迫的表观遗传分子机制不清楚。本研究比较了了两种不同抗旱性花生品种（粤油7和汕优523）在干旱期间根系表型存在差异，经组蛋白去乙酰化酶抑制剂TSA处理后响应干旱，光合效率保持较高，光合作用相关基因AhLHCB3和AhAPRO表达明显上调；粤油7根系的的保水能力好. AhAREB1和AhNCED1基因表达大幅度提高，明显高于汕优523. 组蛋白H3 乙酰化参与了花生响应干旱胁迫的过程， PEG和ABA使抗旱相关基因AhAREB1，AhDHN2和AhNCED1呈现不同程度的上调表达；在H3K14乙酰化位点富集明显。表明干旱和ABA通过提高花生组蛋白乙酰化程度上调抗旱下游基因的表达。超表达AhHDA1的花生毛状根生长缓慢，侧根短小，根尖ROS积累，ABA含量显著降低，影响了细胞对干旱的响应性；与AhHDA1影响苯丙氨酸代谢相关的生物合成途径、光合作用途径和植物激素信号转导途径相关。H3K14是干旱影响花生抗旱相关基因乙酰化修饰的主要位点.异源表达AhHDA1拟南芥植株的抗旱性降低。AhHDA1抑制外源ABA对AhNCED1的诱导表达。AhHDA1蛋白与AhAREB1互作, 其结合AhAREB1启动子近启动子的pA3区域，而干旱或外源ABA处理时pA1、pA2和TSS区域是AhHDA1蛋白影响AhAREB1转录的区域。. AhHDA1的水平影响AhAREB1与AhNCED1启动子结合。而AhHDA1通过反馈调控ABA的生物合成关键酶基因AhNCED1，影响ABA水平，反馈调节ABA信号关键成员AhAREB1和 AhSnRK2的启动子活性参与ABA信号通路，影响干旱胁迫响应。AhHDA1在花生响应干旱胁迫的作用以及ABA信号诱导上调表达的生物学意义，为全面认识AhHDA1功能提供了依据。