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烟草NtDXS2基因的克隆及表达分析

Cloning and expression analysis of NtDSX2 from Nicotiana tabacum

  • 摘要: 1-脱氧-D-木酮糖-5-磷酸合成酶(1-Deoxy-D-xylulose 5-phosphate synthase,DXS)是萜类化合物合成过程中的限速酶。为明确DXS2基因在烟草萜类化合物合成中的作用,利用RACE技术从普通烟草中克隆了NtDXS2基因,分析NtDXS2的序列特征以及NtDXS2在不同组织、水杨酸处理中的表达。结果表明,NtDXS2 cDNA全长2 407 bp,编码713个氨基酸。NtDXS2与番茄DXS2氨基酸序列的一致性最高,为91.1%;与NtDXS1氨基酸序列的一致性为69.2%。亚细胞定位及蛋白结构域预测结果显示,NtDXS2定位于叶绿体,含有DXS的保守功能域。进化分析表明,NtDXS2属于DXS2亚家族,与番茄DXS2亲缘关系最近。qPCR结果表明,NtDXS2在叶中表达量较高,在根和雄蕊中表达量较低,在雌蕊和萼片中几乎不表达。在水杨酸处理下,NtDXS2的表达量升高,推测NtDXS2可能参与烟草叶片腺毛中萜类次生代谢物的合成以及烟草的抗病反应。

     

    Abstract: 1-Deoxy-D-xylulose-5-phosphate synthase (DXS) is a rate-limiting enzyme in the synthesis of terpenoids. To reveal the potential function of DXS2 in tobacco isoprenoid biosynthesis, NtDXS2 was cloned from Nicotiana tabacum by Rapid Amplification of cDNA Ends (RACE) technology. The sequence characteristics and expression patterns of NtDXS2 in different tissues and salicylic acid treated leaves were analyzed. The results showed that the full-length cDNA of NtDXS2 was 2 407 bp, which encoded 713 amino acids. Amino acids sequence of NtDXS2 matched that of tomato DXS2 and NtDXS1 with the identity of 91.1% and 69.2%, respectively. The prediction results of subcellular localization and protein domain indicated that NtDXS2 might be located in chloroplast and contained the conserved domains of DXS. Phylogenetic analysis suggested that NtDXS2 belonged to DXS2 subfamily and had closest genetic relationship with tomato DXS2. qPCR revealed that the expression levels of NtDXS2 were higher in leaves, lower in roots and stamens, and hardly detected in pistils and sepals. The expression level of NtDXS2 increased under salicylic acid treatment. Therefore, NtDXS2 might participate in the terpenoid synthesis in glandular trichomes of tobacco leaves and the reaction against disease of tobacco.

     

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