木薯过氧物酶基因序列分析及其乙烯和茉莉酸甲酯诱导表达特性

材料，利用实时荧光定量PCR（qPCR）检测木薯MePOD基因在乙烯利和茉莉酸甲酯（MeJA）处理后的表达特性。【结果】MePOD基因编码区含4个外显子和3个内含子；转录起始位点位于起始密码子上游1061 bp处；启动子区域含多个顺式作用元件，但无ET和JA响应元件。MePOD蛋白由331个氨基酸组成，分子量为37.476 kD，理论等电点为8.66；有一个含信号肽的跨膜结构，是一种阳离子分泌型Class III POD。系统发育进化树分析结果表明，木薯MePOD蛋白与大戟科橡胶树（Hevea brasiliensis，ADR70870.1）的亲缘关系最近，且除两种裸子植物外，其他17种被子植物聚为一类，且同一科植物进一步相聚，此结果与进化地位一致。qPCR检测结果表明，MeJA诱导0.5 h后，MePOD基因表达量整体上呈先升高后下降的变化趋势，而乙烯利诱導0.5 h后其表达量呈缓慢上升的变化趋势，但整体上维持在本底水平之下。【结论】JA和ET逆境信号不直接通过相应响应元件上调MePOD基因表达，而与其他激素信号进行综合调控，并进一步参与植物体内的抗氧化过程。

关键词： 木薯；过氧化物酶（POD）基因；乙烯（ET）；茉莉酸（JA）；表达分析

中图分类号： S533 文献标志码：A 文章编号：2095-1191（2016）12-2009-06

Abstract：【Objective】The present study was conducted to analyze sequence characteristics of Manihot esculenta Crantz Class III peroxidase gene（MePOD） and detect its expression stimulated by two stress signals viz.， ethylene（ET） and jasmonic acid（JA） in cassava， in order to lay theoretical foundation for studying response of M. esculenta Crantz to stress and breeding new resistant varieties. 【Method】MePOD gene sequence was obtained from Cassava Genome Database. Using suspension cultured cells of M. esculenta Crantz variety SC8 as materials， expression characteristics of MePOD gene were investigated by real-time quantitative PCR（qPCR） technique after being induced by ethephon and methyl jasmonate（MeJA）. 【Result】Results showed that， coding region of MePOD gene contained four extrons and three introns， and its transcription initiation site was located at the upstream 1061 bp of start codon. There were many cis-acting elements excluding JA and ET responsive elements in promoter region of MePOD gene. Furthermore， MePOD protein was composed of 331 amino acids and 37.476 kD in molecular weight， theoretical isoelectric point was 8.66， and it contained a transmembrane structure with a signal peptid， so it was secretory cationic Class III POD. Phylogenetic tree analysis showed that， MePOD protein of M. esculenta Crantz had a close genetic relationship with POD of Hevea brasiliensis（ADR70870.1） belonging to Euphorbiaceae. Seventeen species of angiosperms were clustered into one category except two species of gymnospermae， and the same family was clustered together. The above results were consistent with evolutionary status. qPCR results showed that， MePOD gene expression increased firstly and then decreased after being induced by MeJA for 0.5 h， whereas MePOD gene expression increased slowly but maintained below background level after being induced by ethephon for 0.5 h. 【Conclusion】In the absence of JA and ET responsive elements， MePOD gene can not be up-regulated directly， but can be regulated by integrating different hormones signals， and then participate in antioxidation processes.