西瓜八氢番茄红素合成酶基因全长的克隆与表达分析

Cloning and Expression Analysis of Phytoene Synthase Gene in Watermelon(Citrullus lanatus)

通过RT-PCR和RACE技术从西瓜果实中克隆八氢番茄红素合成酶(PSY)基因的cDNA全长,用生物信息学方法对其cDNA序列及推测氨基酸序列进行分析,并用实时荧光定量PCR技术研究PSY在不同瓤色西瓜果实发育过程中的表达情况.结果表明,PSY基因cDNA全长1 561 bp(GenBank登录号为KC166870),其开放阅读框为1 266 bp,编码421个氨基酸.该基因及其推导的氨基酸序列与同为葫芦科的其他植物的PSY及氨基酸序列的同源性分别为87%和91%以上;序列分析显示,PSY氨基酸序列N末端存在转运肽信号序列.不同瓤色西瓜果实发育过程中PSY的表达存在明显差异,红瓤果实中的表达量最高,这表明PSY可能与红瓤果实中积累较多的类胡萝卜素有关;PSY的表达量均高于PSY-A,推测PSY基因主要负责果实中类胡萝卜素的合成.

Full-length cDNA of phytoene synthase gene （PSY） was cloned from watemelon fruit using RT-PCR and RACE.Bioinformatics methods were used to analyze cDNA obtained and putative amino acid sequence.SYBR Green real-time qPCR method was used to measme the transcript levels of PSY during fruit development and ripening of watemelon in four flesh-colored cuhivars.The results indicated that the full-length cDNA of PSY （GenBank accession number：KC166870） in watermelon consisted of 1 561 bp including an intact open reading frame of 1 266 bp,and encoding a 421 amino acid polypeptide.The nucleotide and deduced amino acid sequences of watemelon PSY shared more than 87 ％ and 91％ similarity with those in the other cucurbitaceous plants,respectively.The deduced protein comprised a putative signal transit peptide for plastid targeting in the N-terminal region.The transcript levels of PSY were different in four flesh-colored watemelon cuhivars,with the highest expression was in redfleshed fruit.It was very likely that the higher expression of PSY might be associated with the massive accumulation of carotenoids in watemelon flesh.The expression levels of PSY were higher than that of PSYA in the fruits.It was suggested that PSY was mainly responsible for carotenoids synthesis in watermelon fruit.