茶树PPO基因家族的鉴定与分析

The Identification and Analysis of Polyphenol Oxidase Gene Family in Tea Plant(Camellia sinensis)

多酚氧化酶(Polyphenol oxidases,PPO)是由核酸编码的一种以氧为受体的含铜金属酶,为一种末端氧化酶,在茶叶加工中也发挥重要的作用。从最新发布的茶树基因组数据库中获得了5条PPO基因:CsPPO1、CsPPO2、CsPPO3、CsPPO4(GenBank登录号为GQ129142.1)、CsPPO5。本研究利用生物信息学方法,对5条基因的核酸序列和氨基酸序列进行分析,并对基因编码蛋白的理化性质和结构功能进行预测。结果表明,5个基因CDS区全长在597～1 839 bp之间,编码氨基酸数目198～612;系统进化树分析显示CsPPO1、CsPPO3、CsPPO4和CsPPO5具有较近的亲缘关系;编码的蛋白均属于亲水性不稳定类脂类结合蛋白,都不具有信号肽;无规则卷曲是蛋白质的主要结构元件,α-螺旋和β-折叠分散于整个多肽链中,CsPPO1、CsPPO2、CsPPO3可能存在一个或多个跨膜螺旋;5个蛋白均含有PPO1_DWL(pfam12142)保守结构域,除了CsPPO2外,其余4个蛋白均预测到TYROSINASE功能结构域。实时定量PCR结果表明,PPOs基因在不同茶树品种间呈现出不同的表达模式。

Polyphenol oxidase(PPO)is a copper-containing metal enzyme,which plays an important role in tea processing.Five PPO genes were found in the tea genome database:CsPPO1,CsPPO2,CsPPO3,CsPPO4(GenBank Access.No.GQ129142.1)and CsPPO5.The nucleic acid and amino acid sequences of five PPO genes were analyzed,and the physicochemical properties and structural functions of the PPO genes encoding protein were also predicted by bioinformatics method.The results showed that the full length of the five PPO genes coding sequences(CDS)was between 597 bp and 1 839 bp which could encode 198-612 amino acids.Phylogenetic tree analysis showed that CsPPO1,CsPPO3,CsPPO4 and CsPPO5 had close genetic relationships.The encoded proteins belonged to hydrophilic and unstable lipid binding proteins and had no s ignal peptides.Irregular curl was the main structural element of protein in whichα-helix andβ-strand were dispersed throughout the polypeptide chain&CsPPO1,CsPPO2,CsPPO3 might contain one or more transmembrane spirals.The five PPO proteins contained PPO1_DWL(pfam12142)conserved structural domains.It was predicted that the proteins encoded by CsPPO1,CsPPO3,CsPPO4 and CsPPO5 might contain tyrosinase functional domains.Real-time reverse transcription(qRT-PCR)analysis showed that the PPO genes showed different expression patterns among different tea cultivars.