胡萝卜S-腺苷甲硫氨酸脱羧酶SAMDC基因的克隆及其对非生物胁迫的响应

Cloning of S-adenosylmethioine decarboxylase gene SAMDC from Daucus carota and its response to abiotic stresses

S-腺苷甲硫氨酸脱羧酶是多胺生物合成过程中的关键酶,对于植物生长发育和抵御逆境胁迫等过程具有重要作用。本研究利用RT-PCR方法从胡萝卜品种‘黑田五寸’中克隆得到一个编码S-腺苷甲硫氨酸脱羧酶的基因Dc SAMDC。序列分析显示,该基因包含一个全长1 086 bp的开放阅读框,编码361个氨基酸。预测其蛋白质相对分子质量为40.16 kDa,理论等电点为4.89。胡萝卜S-腺苷甲硫氨酸脱羧酶具有高度保守的酶原剪切位点和PEST结构域。进化分析表明,胡萝卜SAMDC与葡萄的进化关系最为接近。荧光定量PCR分析显示,胡萝卜Dc SAMDC基因在叶片和根中的表达水平较高,对高温(38oC)、低温(4oC)、模拟干旱(200 g·L^(-1) PEG)和盐渍(200 g·L^(-1) Na Cl)胁迫有响应,并且,响应的时间较为迅速,在胁迫1~4 h后表达水平升至最高。本研究结果表明,Dc SAMDC基因可能在胡萝卜抵御非生物胁迫的过程中发挥重要作用。

S-adenosylmethioine decarboxylase （SAMDC）, a key enzyme involved in polyamine biosynthesis, plays important roles in plant development and resistance against adverse circumstances. In this study, a gene DcSAMDC that encodes S-adenosylmethioine decarboxylase was cloned from carrot cultivar ＇Kurodagosun＇ using RT-PCR. Sequence analysis indicated that the DcSAMDC gene harbored an open reading frame of 1 086 bp encoding 361 amino acids. The relative molecular mass of its protein was predicted to be 40.16 kDa with a theoretical isoelectric point of 4.89. DcSAMDC possesses highly conserved function domains, proenzyme cleavage site and PEST domain. The evolutionary relationship of DcSAMDC was more close to grape （Vitis vi- nifera）. Quantitative real-time PCR analysis indicated that carrot DcSAMDC gene was highly expressed in the leaves and roots. Moreover, this gene can respond to high temperature （38℃）, low temperature （4℃）, PEG-in- duced drought （200 g·L^-1 PEG）, and salinity （200 g·L^-1 NaCl）, and its expression levels were highest from 1 to 4 h after treatment. The results suggested that DcSAMDC gene may play important roles in carrot plant tolerance to abiotic stresses.