刚毛柽柳腺苷甲硫氨酸脱羧酶(ThSAMDC)基因的克隆与胁迫下的表达分析

Cloning and Expression Analysis of S-Adenosine Methionine Decarboxylase(ThSAMDC) Gene from Tamarix ramosissima

S-腺苷甲硫氨酸脱羧酶(S-adenosyl-L-methionine decarboxylase,SAMDC)是一种通过参与多胺的代谢途径来调节植物生理生化过程的限速酶。通过分析刚毛柽柳(Tamarix hispida)的转录组数据,获得并克隆了SAMDC基因的c DNA序列,将其命名为ThSAMDC。该cDNA序列全长2 085 bp,包含tiny ORF(tORF)、upstream ORF(uORF)和main ORF(mORF)3个植物SAMDC基因特征ORF。主开放读码框(mORF)长1 107 bp,编码369个氨基酸多肽,相对分子质量为40.34 k D,理论等电点(PI)为4.72。Th SAMDC编码蛋白具有多个较强的亲水性区域,无明显跨膜区。通过与其他多个物种的氨基酸多序列比对结果表明,ThSAMDC具有两个典型的高度保守的结构域:酶原剪切位点(LSESSLF)与蛋白快速降解有关的PEST(TIHVTPEDGFSYAS)结构域。系统发育树结果表明ThSAMDC与菠菜(SoSAMDC)氨基酸序列一致性最高,为77%。实时荧光定量RT-PCR分析显示,ThSAMDC在NaCl、PEG、ABA、CdCl_2诱导表达均上调,预示着ThSAMDC可能在刚毛柽柳非生物胁迫应答过程中发挥重要作用。

S-adenosyl-L-methionine decarboxylase（SAMDC） is a rate-limiting enzyme that regulates the physiological and biochemical processes of plants by participating in the metabolic pathway of polyamines. The cDNA of S-Adenosine Methionine Decarboxylase gene（named ThSAMDC） was isolated and cloned by analyzing the transcriptome data of Tamarix hispida. The full-length of ThSAMDC is 2 085 bp, with three open reading frames, tiny ORF（tORF）, upstream ORF（uORF） and main ORF（mORF）. The mORF was 1 107 bp encoding 369 amino acids. The relative molecular weight and isoelectric points（PI） of the putative protein were 40.34 kD and 4.72. ThSAMDC-encoded protein has a number of strong hydrophilic regions, no obvious transmembrane region. Compared to the amino acid multiple sequence alignment of several other species, ThSAMDC includes two highly conserved domains： the proenzyme cleavage site（LSESSLF） and the PEST domain（TIHVTPEDGFSYAS） associated with the rapid degradation of the protein. Phylogenetic tree analysis shows that ThSAMDC has higher sequence similarity of 77% identities to the Spinach（SoSAMDC）. Quantitative real-time PCR assay revealed that the mRNA level of ThSAMDC was significantly up-regulated under NaCl, PEG, ABA and CdCl2 treatments in T.hispida, suggesting that ThSAMDC may play an important role in drought resistance, salt tolerance and other stresses.