郑威 孙文文 董学明 张秋颖 于雪飞 陈宁

摘 要： 為研究八氢番茄红素合成酶（phytoene synthase）基因在龙眼类胡萝卜素合成途径中的作用机制，该文从龙眼转录组数据中筛选获得一个PSY基因，命名为DlPSY，采用生物信息学方法对龙眼PSY蛋白的一级结构、理化性质、信号肽、跨膜结构、亚细胞定位、亲疏水性、蛋白质二级结构、蛋白质三级结构、卷曲螺旋、蛋白质结合位点、系统进化树、蛋白质互作等进行分析和预测，并同时运用实时荧光定量PCR（RT-qPCR）技术对DlPSY基因在龙眼根和叶中的差异表达进行分析。结果表明：龙眼DlPSY基因长度为1 260 bp，编码420个氨基酸;生物信息学预测DlPSY蛋白具有Isoprenoid Biosyn C1超家族结构，含有信号肽，为分泌性蛋白，无跨膜结构，是一种可溶性亲水蛋白，定位于膜外;DlPSY蛋白的二级结构主要由α-螺旋和无规则卷曲组成，具有卷曲螺旋。Ramachandran评估结果表明应用SWISS-MODEL构建的蛋白质三级结构模型可靠，其配体结合位点为344Phe和347Lys。RT-qPCR分析结果表明DlPSY基因在龙眼根和叶中均有表达，叶中表达量高于其在根中的表达量。该研究结果为下一步采用遗传学方法提高龙眼中类胡萝卜素的含量奠定理论基础。

关键词： 龙眼， DlPSY基因， 生物信息学， 基因表达

中图分类号： Q943

文献标识码： A

文章编号： 1000-3142（2021）04-0546-13

Abstract： To study the function of phytoene synthase gene in carotenoid synthesis of Dimocarpus longan Lour. （D. longan）， a DlPSY gene identified from D. longan RNA-seq data was screened and analyzed in this research by bioinformatics methods including the primary structure of protein， physicochemical properties， signal peptide， transmembrane structure， subcellular localization， hydrophilicity， protein secondary structure and tertiary structure， coiled coil， protein binding site， phylogenetic tree， as well as protein-protein interaction. In addition， the real-time quantitative PCR （RT-qPCR） was applied in this research to analyze the expression pattern of DlPSY gene in root and leaf tissues. The bioinformatics software used in this research included NCBI BLAST， DNAMAN， NCBI CD search， Protparam， SignalP 4.1 Server， TMHMM Server， SOSUI， PSORT， ProtScale， SOPMA， COILS， SWISS-MODEL， MolProbity， 3DLigandSite， and STRING. The bioinformatics analysis results were as follows： The length of the DlPSY gene was 1 260 bp， coding for 420 amino acids; the DlPSY protein was predicted to have ‘Isoprenoid Biosyn C1 superfamily structure， contained a signal peptide， did not contain the transmembrane structure， and was a soluble hydrophilic and secretory protein which was predicted to be located outside the membrane; the DlPSY protein secondary structure was predicted to be mainly composed of α-helix and random coil; the DlPSY protein was predicted to have a coiled coil. The Ramachandran evaluation results showed that the tertiary structure model constructed by SWISS-MODEL was reliable， and its ligand binding sites were 344Phe and 347Lys， respectively. In addition， the expression pattern of the DlPSY gene was analyzed by RT-qPCR， the results of which showed that the DlPSY gene was expressed in roots and leaves of D. longan but with the different expression levels. The expression level of DlPSY gene was higher in leaves than that in roots. The results of this study will enrich our knowledge on PSY gene family and also lay a foundation for further improving the carotenoid content in D. longan by genetic methods.

Key words： Dimocarpus longan ， DlPSY gene， bioinformatics， gene expression

龙眼（Dimocarpus longan），又名桂圆、益智，味甘、淡，性平，属于无患子科常青果树，具有清热解毒之功效（黄春燕等，2019）。龙眼原产于我国南方，是主要的栽培水果之一，但在泰国、印度和越南等地也有广泛的种植（Campbell & Campbell，2001;Jiang et al.， 2002）。龙眼中含有丰富的膳食纤维、维生素、蛋白质、多糖和……