组蛋白乙酰化修饰由组蛋白乙酰化酶(histone acetyltransferases,HATs)和脱乙酰化酶(histone deacetylase,HDACs)共同催化完成,是重要的表观遗传调控方式之一,在植物生长发育、逆境胁迫响应和激素响应的调控过程中均具有重要意义,但对茶树(Camellia sinensis)组蛋白乙酰化修饰的研究还比较少.本研究从'福鼎大白茶'茶树中克隆获得了 2 个HATs家族的MCC(MEIOTIC CONTROL OF CROSSOVERS)基因:CsMCC1 和CsMCC2,通过生物信息学分析、实时荧光定量PCR技术(Real-time quantitative PCR,qRT-PCR)和亚细胞定位试验对其功能进行解析.结果显示,CsMCC1 和CsMCC2 基因分别位于茶树 1 号和 7 号染色体,分别编码 257 aa和 269 aa,均属于碱性不稳定亲水性蛋白,与拟南芥AtMCC1 具有高度相似的基因结构和蛋白空间结构.系统进化树和保守结构域分析表明,CsMCC蛋白与葡萄、番茄的同源蛋白有较近的亲缘关系,MCC蛋白序列高度保守,均含有GNAT保守结构,属于HAT蛋白的GNAT(GCN5-related N-terminal acetyltransferases)亚家族.拟南芥原生质体亚细胞定位结果显示,CsMCC1和CsMCC2蛋白均定位于细胞质膜.启动子分析显示,在CsMCC1 和CsMCC2 基因启动子中包含多个与胁迫、光和植物激素调节响应相关的元件.转录组数据和表达分析发现,CsMCC1 基因在叶、花和根发育早期的表达量明显高于后期;CsMCC2 基因在茶树根部有最高表达,并在根部发育的较长阶段均有较高水平的表达量;2 个CsMCC基因均能够被多种非生物胁迫(干旱、盐和冷)和外源激素(MeJA、GA3 和 IAA)诱导表达.蛋白相互作用预测分析显示,CsMCC 蛋白与多个乙酰化转移酶相关蛋白具有关联性.综上所述,CsMCC1 和 CsMCC2 基因具有通过组蛋白乙酰化修饰作用广泛参与茶树的生长发育和环境响应过程的潜能,可为进一步研究CsMCC基因在茶树中的功能提供理论参考.
Histone acetylation is an essential type of epigenetic modifications,which is mainly catalyzed by histone acetylases(HATs)and deacetylases(HDACs)and plays a crucial role in plant growth,stress response,and hormone regulation.However,little research information is available about tea plants histone acetylases.We cloned two MCC(MEIOTIC CONTROL OF CROSSOVERS)genes(CsMCC1 and CsMCC2)of HATs family from the'Fuding Dabaicha'tea plant.Meanwhile,the function of these two CsMCC genes was analyzed by bioinformatics methods,qRT-PCR,and subcellular localization.Results showed that the CsMCC1 and CsMCC2 genes were located on chromosomes 1 and 7,encoding alkaline unstable hydrophilic proteins of 257 and 269 amino acids,respectively.The CsMCC genes and protein structure of tea plant were similar to those of the Arabidopsis AtMCC1 gene.The phylogenetic tree and conserved structural domain analysis showed that the MCC protein belonged to the GNAT(GCN5-related N-terminal acetyltransferases)subfamily of HATs proteins,and contained GNAT conserved structures.The evolutionary relationship of CsMCC proteins was closely related to the MCC members in grapes and tomatoes with the highly conserved protein sequences.The subcellular localization in Arabidopsis protoplasts revealed that the CsMCC1 and CsMCC2 proteins were localized on the cytoplasmic membrane.And the promoters of CsMCC1 and CsMCC2 genes contained a number of elements involved in responses to stress,light,and phytohormones.According to transcription data and expression analysis,the relative expression level of CsMCC1 gene was significantly higher in the younger stages of leaf,flower,and root development than the older stages,and CsMCC2 gene was higher in root than other tissues and lasted for a longer time during root development period.The CsMCC1 and CsMCC2 could be regulated by various abiotic stresses(drought,salt,and cold)and exogenous hor-mones(MeJA,GA3,and IAA).In addition,CsMCC proteins could interact with acetyltransferase-related proteins.Hence,CsMCC genes might play roles in tea plant growth and development,and the response to environment through histone acetylation modification.This study explored the basic features and functions of CsMCC,providing the useful theoretical reference for further research on the functions of CsMCC genes in tea plant.