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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-adenosylmethionine decarboxylase is the key enzyme in the biosynthesis of polyamines and plays an important role in the process of plant growth and the defense against stress. In this study, Dc SAMDC, a gene encoding S-adenosylmethionine decarboxylase, was cloned from carrot Variety “Kuroda 5” by RT-PCR. Sequence analysis showed that the gene contained an open reading frame of 1 086 bp, encoding 361 amino acids. The predicted relative molecular mass of the protein was 40.16 kDa and the theoretical isoelectric point was 4.89. Carrot S-adenosylmethionine decarboxylase has a highly conserved zymogen cleavage site and a PEST domain. Evolutionary analysis showed that evolutionary relationship between carrot SAMDC and grape is the closest. Quantitative real-time PCR analysis showed that the expression level of Dc SAMDC gene in leaves and roots was higher than those in roots and leaves, 200 g · L -1 NaCl), and the response time was faster. The expression level increased to the highest level after 1 to 4 h of stress. The results of this study suggest that Dc SAMDC may play an important role in the defense against abiotic stresses in carrot.