茶树PSY基因的比较基因组学及在黄化种中的表达

Comparative genomics of PSY gene and its expression in albino tea cultivars

八氢番茄红素合成酶(PSY)是类胡萝卜素合成途径上的第一个限速酶,本研究旨在探索PSY基因的序列特征及其在黄化茶树新梢中的表达模式.在茶树品种‘黄棪’基因组中鉴定到3个PSY基因,分别命名为CsPSY1、CsPSY2、CsPSY3;从‘铁观音’基因组中鉴定到2个PSY基因,分别命名为TGY-PSY1、TGY-PSY2;从‘舒茶早’基因组中鉴定到4个PSY基因,分别命名为CSS-PSY1、CSS-PSY2、CSS-PSY3、CSS-PSY4.利用生物信息学和实时荧光定量PCR技术对其进行分析,结果表明,茶树PSY基因编码的蛋白序列长度为645~1506 bp,氨基酸个数为214~501,其中,CsPSY1、TGY-PSY1和CSS-PSY1编码的蛋白序列长度均为1269 bp,氨基酸个数均为422.亚细胞定位预测结果显示,CsPSY3和CSS-PSY2分别定位于细胞膜和线粒体上,其他茶树PSY基因均定位在叶绿体上.CsPSY1、CsPSY2和CsPSY3编码的蛋白分别有2、1、0个无序化区域以及41、27、19个磷酸化位点.无规则卷曲和α-螺旋是PSY蛋白的主要组成部分.CsPSY1编码的蛋白与柿子、木瓜、葡萄等具有较高的同源性.启动子区域分析结果显示,茶树PSY基因存在大量与植物光响应、生长作用、激素、胁迫等响应相关的顺式作用元件.实时荧光定量PCR检测结果显示:PSY基因在‘黄金芽’中有较高的表达量;CsPSY1在福黄1号中的表达量较高,是‘福安大白茶’的37.56倍;CsPSY2在福黄2号中的表达量较高,是‘福云6号’的141.43倍.研究表明,PSY基因在茶树黄化种中的表达量显著上调,推测PSY基因可能是茶树黄化种中类胡萝卜素合成的重要调控因子.

Phytoene synthase(PSY)is the first enzyme that limits the rate of carotenoid biosynthetic pathway.In this study,the sequence characteristic of the PSY gene and its expression pattern in albino tea plants were explored.Genomic analysis identified 3 PSY genes(CsPSY1,CsPSY2,CsPSY3)in tea cultivar‘Huangdan’,2 PSY genes(TGY-PSY1,TGY-PSY2)in‘Tieguanyin’and 4 PSY genes(CSS-PSY1,CSS-PSY2,CSS-PSY3,CSS-PSY4)in‘Shuchazao’.Bioinformatics analysis and real-time fluorescence quantitative PCR(RT-PCR)showed that the lengths of the PSY genes ranged from 645 to 1506 bp,and the encoded proteins contained 214-501 amino acids.Among them,the CsPSY1,TGY-PSY1,and CSS-PSY1 were all 1269 bp in length.Subcellular location prediction demonstrated all the PSY proteins were mostly located in the chloroplast except CsPSY3 and CSS-PSY2,which were located in cell membrane and mitochondria,respectively.Proteins CsPSY1,CsPSY2 and CsPSY3 consisted of 2,1,and 0 disordered regions and 41,27,and 19 phosphorylation sites,respectively.Random coils andα-helices were the primary components in PSY proteins.CsPSY1 was highly homologous with that of Diospyros kaki,Carica papaya and Vitis vinifera.Promoter region analysis detected a large number of cis-acting elements related to plant light response,growth effect,hormone and stress response in the PSY genes.RT-PCR analysis further showed that the PSY genes were highly expressed in‘Huangjinya’,the expression level of CsPSY1 in Fuhuang was 37.56 times of that in‘Fuan Dabaicha’,and the expression level of CsPSY2 in Fuhuang 2 was 141.43 times of that in‘Fuyun 6’.To summarize,the expressions of the PSY genes were significantly up-regulated in the albino tea,which indicated the important role of PSY genes in the regulation of the carotenoid synthesis in albino tea cultivars.