镉对草莓幼苗根尖氧化系统和基因组DNA损伤的影响

采用随机扩增多态性DNA（RAPD）技术和生理生化方法检测镉胁迫对草莓幼苗根尖氧化系统和DNA多态性的影响。结果表明，用5、10和15 mg · L-1镉（CdCl2 · 2.5H2O）处理6 d后，草莓幼苗根伸长及根系中可溶性蛋白质含量均受到抑制，根尖活性氧爆发（超氧阴离子产生速率升高和过氧化氢含量增加），超氧化物歧化酶、过氧化物酶和过氧化氢酶活性下降，DNA增色效应减少。选用8条寡核苷酸引物（10 bp）对草莓幼苗根尖细胞中基因组DNA进行RAPD扩增，对照组图谱中可分辨出88条RAPD谱带，其分子量为150 ~ 3 500 bp，处理组与对照组RAPD图谱之间存在明显差异，且与镉浓度之间存在剂量效应关系。镉影响草莓幼苗根尖细胞中基因组模板的稳定性，活性氧爆发和DNA交联是根尖DNA损伤的主要原因，利用RAPD技术获得的DNA多态性变化可作为检测草莓根尖DNA损伤的指标。

Effects of Cadmium Stress on Oxygen Enzyme System and Genome DNA Polymorphism in the Root Tips of Strawberry Plants

Fragan × ananassa Duch.‘Toyonoka’plants were exposed to 5，10 and 15 mg · L-1 cadmium（CdCl2 · 2.5H2O）for 6 d to investigate the influence of heavy-metal Cd on root tips，which included DNA polymorphism change and oxidation systems damage. In addition，above indexes were analyzed by physiology biochemistry methods and random amplified polymorphic DNA（RAPD）technology. Cd induced an inhibited effect on root growth and soluble protein content，which also accumulated reactive oxygen species outbreak including superoxide anion production rate increased and hydrogen peroxide content enhanced. At the same time，antioxidant enzymes（SOD，POD and CAT）activities also decreased. Moreover，DNA hyperchromic effect reduced after 6 d on 5，10 or 15 mg · L-1 Cd treatment. Finally，RAPD results showed that 8 primers gave a total of 88 RAPD bands ranging from 150 to 3 500 bp in molecular size in the normal plantlets. The changes occurring in RAPD profiles of the root tips after Cd treatment， which included loss of normal bands，appearance of new bands and variation in band intensity in comparison to which of the plantlets without treatment. It is need to point out that the RAPD band change effect was dose-dependent of Cd concentration. These results indicated that genomic template stability（a qualitative measure reflecting changes in RAPD profiles）was significantly affected by the above Cd concentrations. Reactive oxygen species outbreak and DNA cross-linking were the main reasons which causing the root tips damage. Thus，DNA polymorphisms detected by RAPD analysis could be used as an effective method for the assessment of the root tips damage by Cd in strawberry plantlets.