镉胁迫对不结球白菜Vc合成L-半乳糖途径基因表达及抗氧化系统的影响

Effects of Cadmium Stress on Genes Expression in L-Galactose Pathway Involved in Vc Biosynthesis and Antioxidant System of Brassica campestris ssp. chinensis

为了探究Cd^2＋胁迫对不结球白菜的种子萌发以及L-半乳糖途径基因表达、抗坏血酸（L-ascorbic acid，AsA）含量及抗氧化酶等指标的影响，以不结球白菜品种‘苏州青’为材料，设定不同浓度的Cd^2＋处理种子和幼苗。结果表明，Cd^2＋胁迫对不结球白菜种子萌发时胚根的损伤随Cd^2＋浓度的增加而加重；AsA含量在6～12h内持续升高，24h时显著降低，48h时，Cd^2＋胁迫的AsA含量均显著低于对照，总AsA含量与对照差异不显著。L-半乳糖途径多个基因的表达量均与AsA含量变化保持一致。PMI和GGP对50μmol·L^-1 Cd^2＋胁迫较为敏感，在Cd^2＋胁迫12h达到峰值；PMM,GMP、GPP、GalDH和GalLDH对100μmol·L^-1Cd^2＋胁迫响应较为迅速，在Cd^2＋胁迫后6h达到峰值；胁迫5d时，SOD在抗氧化酶系统中起主要防御功能；胁迫10d时，POD、CAT和APX清除活性氧的效率要高于SOD；MDA含量随Cd^2＋浓度增大和Cd^2＋胁迫时间延长显著急剧升高；胁迫10d时，Cd^2＋胁迫的叶绿素含量均显著低于对照水平。这表明Cd^2＋胁迫对不结球白菜的形态发育及抗氧化系统均造成了不同程度的损伤，对抗坏血酸合成相关基因的表达造成了不同程度的影响。

In order to investigate the effects of Cd^2＋ stress on the seed germination, genes expression in the L-galactose pathway, AsA content and antioxidant enzymes and other indicators in non-heading Chinese cabbage （Brassica carnpestris ssp. chinensis）, we used non-heading Chinese Cabbage ＇Suzhouqing＇ as material, and set different concentrations of cadmium treatments of seeds and seedlings. The results showed that the radi- cles injury of germinated seeds under Cd^2＋ stress aggravated along with the increase of Cd^2＋ concentration. The contents of AsA continued to rise during 6-12 h, then significantly decreased at 24 h, which were significantly lower than that of the control at 48 h, while total AsA contents had no significant difference with the control. The expression of most genes in the L-galactose pathway were consistent with AsA contents, PM/and GGP were sensitive to 50 μmol·L^-1 Cd^2＋ stress, and reached the peak at 12 h after treatment; PMM, GMP, GPP, GaIDH and GalLDH responded swiftly to 100μmol·L^-1 Cd^2＋ stress, which showed the peak values at 6 h after treatment. SOD played the main role of defense in the antioxidant system after 5 d treatment, while the ROS scavenge efficiencies of POD, CAT and APX were higher than that of SOD after 10 d treatment; the contents of MDA increased sharply along with the increase ofCd^2＋ concentration and the extension of treatment time; chlorophyll contents with Cd^2＋ treatment were significantly lower than that of the control eventually. These results revealed that cadmium stress made the damage to morphological development and antioxidant system in non-heading Chinese cabbage, and also made different effects on genes expression in AsA biosynthesis pathway.