摘 要: 异戊烯基焦磷酸异构酶(isopentenyl diphosphate isomerase, DvIPI)是绿色杜氏藻中类胡萝卜素等萜类物质合成过程中甲羟戊酸途径(mevalonate pathway, MVA)通路上一个重要的限速酶。实验中获得绿色杜氏藻IPI基因的全长序列(GenBank序号: KX189195), 该基因全长4 641 bp, 开放阅读框(ORF)为1 147 bp, 编码382个氨基酸, 并含有3个CBS结构域。蛋白质预测结果表明, DvIPI分子呈亲水性, 不含信号肽, 也不存在跨膜区域; 同时, DvIPI中α-螺旋所占比例最高, 中部呈现不规则的扭曲缠绕, 两边各自有一个扭曲的多肽链单独远离中心。系统进化树分析显示, DvIPI与细菌IPI亲缘关系较近, 而与被子植物以及其他藻类IPI亲缘关系较远。定量检测结果与RT-PCR结果表明, 茉莉酸甲酯(methyl jasmonate, MeJA)浓度为50~100 μmol/L时, 对绿色杜氏藻类中类胡萝卜素含量、叶绿素含量以及绿色杜氏藻IPI基因表达水平的影响最为明显, 且三者的变化趋势基本一致, 推测MeJA对绿色杜氏藻类中类胡萝卜素、叶绿素的诱导作用可能与绿色杜氏藻类IPI基因有关。

Abstract: Isopentenyl diphosphate isomerase (DvIPI) is an important rate-limiting enzyme involved in mevalonate synthesis pathway of Dunaliella viridis, which limits the biosynthesis of terpenoids such as carotenoid. Here, the full-length cDNA sequence of IPI gene (GenBank number: KX189195) in D. viridis was obtained and its protein structure and function were analyzed. The full-length IPI gene of D. viridis was 4 641 bp long, had an open reading frame of 1 147 bp with 3 CBS domains and encoded 382 amino acids. The protein prediction results showed that DvIPI was hydrophilic, without a signal peptide and transmembrane domain, and had the highest proportion of alpha helix and irregular twist in the middle. What’s more, both sides of DvIPI had a twisted polypeptide chain far from the center. According to phylogenetic analysis, DvIPI had a close homologous relationship with bacterial IPI, but had little relationship with those of angiosperms and other algae. Quantitative detection and RT-PCR showed that the effects on carotenoid and chlorophyll contents and the expression level of IPI in D. viridis were the most obvious when MeJA concentration was between 50 μmol/L and 100 μmol/L, and that their trends were basically the same. This suggests that the induction of carotenoid and chlorophyll by MeJA might be associated with IPI gene in D. viridis.