甜瓜S-腺苷甲硫氨酸脱羧酶基因的克隆及白粉病诱导表达分析

Cloning and analysis of a powdery mildew responsive gene CmSAMDC from Cucumis melo L.

摘要:

为探讨S-腺苷甲硫氨酸脱羧酶 (S-adenosylmethionine decarboxylase，SAMDC) 基因在甜瓜抵御白粉病菌中的作用，根据已知EST序列和甜瓜基因组数据库，在甜瓜抗白粉病品种‘Yuntian930’中克隆获得该基因的全长编码序列，命名为CmSAMDC (GenBank登录号为KF151861)。生物信息学分析表明，CmSAMDC 的主开放阅读框 (mORF)长1 095 bp，编码364个氨基酸，预测分子量为40 kDa。聚类分析表明，CmSAMDC预测蛋白与黄瓜和四季橘中该蛋白的同源关系最近，并与其他双子叶植物聚为一类。原核表达分析表明，CmSAMDC以融合蛋白形式表达，相对分子量约为40 kDa，与预测一致。实时定量表达分析表明，CmSAMDC基因受白粉病诱导表达，在接种后48 h表达量达到峰值，为接种前的7倍，并且在甜瓜的根、茎、叶、卷须中均有表达。结果提示该基因可能参与了甜瓜的抗白粉病反应。

Abstract:

In order to investigate the effect of S-adenosylmethionine decarboxylase (SAMDC) gene in melon resistance to powdery mildew, according to the previous results of EST sequences from cDNA-AFLP library and the melon genome sequence data, the SAMDC gene was isolated from Chinese wild melon clone ‘Yuntian930’ by RT-PCR and designated as CmSAMDC (GenBank Accession No. KF151861). The mORF (main open reading frame) was 1 095 bp encoding 364 amino acids with a molecular mass of 40 kDa. The predicted protein sequence showed high similarity with Cucumis sativus and Citrofortunella microcarpa. The SDS-PAGE showed that the expression protein was a fusion protein with the molecular weight of 40 kDa, which perfectly matched the mass calculated from the amino acid sequence. Quantitative real-time PCR analysis indicated that the expression level of CmSAMDC reached a maximum at 48 hpi (hours post inoculation) that over 7-fold to 0 hpi, and the expression of CmSAMDC was also detected in tendril, root, leaf and stem. These results indicate that CmSAMDC gene may play protective roles in melon resistance to powdery mildew infection.