白菜S-腺苷甲硫氨酸脱羧酶BrSAMDC基因的克隆、表达及生物信息学分析

S-腺苷甲硫氨酸脱羧酶(S-adenosylmethionine decarboxylase,SAMDC)是生物体内亚精胺合成过程中的限速酶,在植物生长发育及抗逆境胁迫方面起到重要的调节作用。本研究通过RT-PCR技术从大白菜栽培种Chiifu-401中克隆得到一个BrSAMDC基因,并对其进行表达特性及其蛋白的结构与功能进行生物信息学分析。结果表明,BrSAMDC的cDNA扩增序列为1566 bp,CDS区为1107 bp,编码368个氨基酸。定量PCR结果显示,BrSAMDC基因在白菜的各个组织均有较高表达,其中角果中的表达量最高,其次为花、茎和根,而在叶片中的表达量最低。BrSAMDC蛋白分子量为40.52 kD,属于亲水、稳定蛋白;预测其分布于细胞核内,不存在信号肽和跨膜结构域;二级结构中以无规则卷曲和α-螺旋为主,三级结构同源建模成功。14种植物SAMDC蛋白的序列对比分析显示,均含有LSESSLF结构域和PEST结构域,且十分保守;十字花科的SAMDC蛋白同源性较高,且其氨基酸的进化与植物分化具有一致性。本研究为白菜SAMDC基因的功能研究及应用提供数据基础。

Cloning,Expression and Bioinformatic Analysis of S-adenosylmethionine Decarboxylase Gene from Chinese Cabbage

S-adenosylmethionine decarboxylase(SAMDC)is a key rate-limiting enzyme in the polyamine synthesis pathway,and plays an important role in plant development and stress tolerance.In this study,a BrSAMDC gene was cloned from Chinese cabbage cultivar Chiifu-401 by RT-PCR and its expression was characterized relative bioinformatics analysis was performed.The results showed that the cDNA sequence of BrSAMDC is 1566 bp,and the CDS region is 1107 bp encoding 368 amino acids.The molecular weight of deducted protein of BrSAMDC is 40.52 kD.It is a hydrophilic and stable protein.This protein has no transmembrane domain and no signal peptide.Predicted subcellular localization is mainly in the nucleus.The secondary structure is dominated by random coil andα-helix,and the tertiary structure homology modeling is successful.Sequence comparison analysis of 14 SAMDC proteins showed that they all contain LSESSLF domain and PEST domain and are very conservative.The SAMDC protein of Brassicaceae has high similarity,and its amino acid diversity is consistent with plant differentiation.Quantitative PCR results showed that the BraSAMDC gene was highly expressed in all tissues of Chinese cabbage,and the highest expression was in the pods,followed by flowers,stems and roots,and the lowest expression in leaves.This study laid the foundation for the functional research and application of the cabbage SADMC gene.