天然无咖啡碱茶叶N-甲基转移酶基因克隆与序列分析

Cloning and Sequence Analysis of N-methyltransferase in Camellia ptilophylla Chang

本研究以天然无咖啡碱南昆山毛叶茶为主要研究材料,以不同咖啡碱含量的英红9号茶树品种和红山茶等山茶属植物为对照,采用RT-PCR技术,克隆获得南昆山毛叶茶、英红9号和福云6号茶树品种的NMT基因全长,分别编码365、369和369个氨基酸。序列比较分析表明南昆山毛叶茶NMT基因与其它茶树NMT基因的核苷酸序列同源性高于86.5%,氨基酸序列同源性高于86.3%,并包含了六个保守序列、三个SAM结合区A、B’、C及一个保守域VFFF。基于同源性比较,推测核苷酸序列的差异可能是导致南昆山毛叶茶NMT基因活性改变、影响茶树体内咖啡碱代谢的原因之一。

In this study, with complete coding sequences （CDS） of N-methyltransferase （NMT） genes, the tea varieties of Camellia.sinensis var. assamica.cv, yinghong 9, Camellia sinensis cv. Fuyun 6 and Camellia ptilophylla chang were cloned with RT-PCR, and the deduced amino acid sequences were 365aa, 369aa and 369aa respectively. The cDNA sequences of NMT were analysed and compared with other NMT. The NMT genes obtained from Camellia show above 86.5% homology in DNA sequence and above 86.3% in amino acid sequence, while all the cDNA include six conserve sequences, three SAM combined region of A, B＇, C and one VFFF conserve domain. Based on sequence homology comparisons, the differences in DNA sequence of Camellia ptilophylla chang are presumed to have changed the NMT substrate specificity and led to different accumulation of purine alkaloids.