茶树7个褪黑素合成酶基因的鉴定及非生物胁迫响应

Isolation and expression analysis of melatonin biosynthesis genes in tea plant in response to abiotic stress

褪黑素(MT)在植物生长发育及逆境胁迫响应中发挥重要功能,而茶树中MT合成途径中相关基因仍有待挖掘.以‘福鼎大白’茶树品种为材料,采用RT-PCR技术克隆MT合成途径相关酶的编码基因:色氨酸脱羧酶(TDC)、色胺-5-羟化酶(T5H)、5-羟色胺-N-乙酰转移酶(SNAT)和N-乙酰基-5-羟色胺-甲基转移酶(ASMT),对它们的生物信息学特征进行分析,并研究它们在不同组织及非生物胁迫下的表达模式.结果显示,共获得7个MT合成酶基因,即CsTDC1、CsTDC2、CsT5H1、CsSNAT1、CsSNAT2、CsASMT1和CsASMT2;蛋白质特征分析显示,MT合成途径相关酶的编码基因主要定位在叶绿体或胞质中,同时发现CsT5H1含有信号肽输出位点及2个跨膜结构域;进化树分析显示,MT合成酶相关的氨基酸序列主要与中华猕猴桃、欧洲大叶杨、胡桃等木本植物亲缘关系较近.组织表达特异性分析显示,CsASMT1在根中表达量较高,其余基因在叶或茎中的表达量较高.在盐和干旱胁迫处理下,这些基因的表达被显著抑制.本研究表明茶树MT合成途径受逆境胁迫调控,结果可为后续研究MT在茶树生长发育及抗逆调控中的作用提供参考.(图4表2参32)

Melatonin(MT) is important for plant growth, development regulation, and stress response. However, the relevant genes involved in the MT biosynthesis pathway in the tea plant remain to be explored. In this study, the MT biosynthesis genes, including those for tryptophan decarboxylase(TDC), tryptophan hydroxylase(T5H), serotonin-N-acetyltransferase(SNAT), and 5-serotonin-N-acetyltransferase(ASMT) were cloned from the tea plant of the ‘Fudingdabai’ cultivar using RT-PCR technology. The sequence characteristics were analyzed using various bioinformatics tools. The expression patterns of the tested genes in tissues and in stress conditions were detected using quantitative real-time RT-PCR(qRT-PCR). Seven genes were isolated and named as CsTDC1, CsTDC2, CsT5 H1, CsSNAT1, CsSNAT2, CsASMT1, and CsASMT2, respectively. Protein sequence analysis showed that these proteins are mainly localized on the chloroplast and or cytoplasm. CsT5H1 was predicted to have a transit signal peptide and two transmembrane domains. Phylogenetic tree analysis showed that these genes were closely related to that of Actinidiachinensis, Populustrichocarpa, and Juglansregia. The qRT-PCR analysis indicated that CsASMT1 was predominantly expressed in roots, whereas the rest of the genes had high expression levels in leaves or stems. Additionally, their trans abundance was repressed in response to salt stress and drought treatments. These results revealed that the MT biosynthesis pathway was regulated by stress stimuli, and provided a fundamental clue for further studies on MT’s role in the tea plant’s growth, development, and stress response.