摘要：

外源施加植物甾醇衍生物-油菜素内酯的信号物质可以显著提高植物的耐盐性。为了检测过表达编码植物固醇关键酶的甲基固醇加氧酶基因(SMO)是否能提高目标植物的盐胁迫耐受性,使用子房注射法,首先将植物甾醇生物合成过程中关键酶-甲基甾醇单加氧酶的编码PnSMO1.1基因转移到裂叶牵牛中,构建了该基因的过表达转基因株系。接着以经PCR鉴定验证的转基因植物株系幼苗为试验材料,在0~200 mmol/L 梯度NaCl处理条件下,检测了不同株系植物的根长和下胚轴长度等生长参数,以及叶片细胞中丙二醛(MDA)的含量、相对电导率、油菜素甾酮和6-脱氧油菜素甾酮含量等生理指标。结果显示,在100~250 mmol/L NaCl处理下,与野生型(WT)植株或空质粒转化对照(BL)植株相比,过表达PnSMO1.1显著增加了转化植株的根和下胚轴的相对生长量,增强了转基因株系的耐盐性。另外,与WT和BL幼苗相比,在不同的NaCl浓度处理条件下,转基因株系中6-脱氧油菜素甾酮的积累显著增加,但相对电导率(rEC)值、油菜素甾酮的积累量或MDA含量均显著降低。盐渍化、干旱和低温等事件的发生,严重抑制了植物的营养生长和产量。这些结果揭示,过表达PnSMO1.1基因,可以通过调节细胞内的油菜素内酯化合物积累量的动态,进而保护质膜的结构完整性,显著提高转基因植物的耐盐性。

关键词: 裂叶牵牛, PnSMO1.1, 遗传转化, NaCl, 盐胁迫, 子房注射

Abstract:

Application of some hormonal signaling compounds,as brassinolides and their derivatives,could significantly improve the salt stress resistance in plants.The purpose of present work was to test whether the over-expressing of Methylsterol monooxygenase gene(SMO),a key gene coding a bio-synthesizing enzyme of sterol in plants,could promote the salt-stress tolerance of target plants.PnSMO1.1,gene encoding of methylsterol monooxygenase in the plant species of Pharbitis nil was firstly cloned and then used as target gene for following genetic transformation process,while wild-type Pharbitis nil seedlings were used as the receptor plants for constructing of the transgenic lines which over-expressed PnSMO1.1 genes.In this work,the PnSMO1.1 gene transformed Pharbitis nil lines were constructed via an ovary injection transformation method.Plantlets from individual PCR identified transgenic plant lines were used as materials to detect vegetative growth figures and some pivotal physiological indicators,for instance,contents of malondialdehyde (MDA),relative conductivity,as well as castasterone and 6-deoxo-castasterone contents in cells under stresses with gradient NaCl conditions varied from 0—200 mmol/L.The results showed that the over-expression PnSMO1.1 significantly improved the relative growth of roots and hypocotyls in transformants than in wild-type (WT) or vacant plasmid transformed control (BL) plants under 100—250 mmol/L NaCl stresses.Compared to WT and BL seedlings,significantly higher accumulation of 6-deoxo-castasterone,but lower relative conductivity (rEC) values,castasterone accumulation or MDA contents were found in transgenic lines under various NaCl stresses.Stresses such as salinity,drought and freezing temperatures,had severely suppressed the vegetative growth of plants,as well as their yields.These results highlighted that over-expression of the PnSMO1.1 gene could significantly improve the salinity-stress resistance of transgenic plants by delicately adjusting the dynamic homeostasis of brassinolides in cells,and protecting the structural integrity of plasma membrane.

Key words: Pharbitis nil, PnSMO1.1, Genetic transformation, NaCl, Salt stress, Ovary injection