油菜素内酯对龙葵幼苗Cd毒害耐受性的影响
Effects of exogenous brassinosteroid on Cd tolerance in Solanum nigrum seedlings
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摘要: 以重金属超富集植物龙葵为试验材料, 分析了油菜素内酯(BR)对幼苗镉(Cd)毒害耐受性影响的生理机制。Cd毒害导致龙葵幼苗出现氧化伤害, 同时降低了幼苗超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性。表油菜素内酯(eBL, 人工合成的BR)处理增加了龙葵幼苗对Cd毒害的敏感性, 与eBL处理的结果相反，施用油菜素唑(Brz, BR合成的特异性抑制剂)增加了Cd毒害下龙葵幼苗的抗氧化酶活性, 降低了ROS的累积, 减少了幼苗的氧化伤害。Brz处理后幼苗株高和根长较Cd处理的对照分别增加29%和28%, MDA水平和Evans blue染色程度较Cd处理的对照分别降低37%和20%, 进一步证明BR增加了Cd毒害下龙葵幼苗的氧化伤害, 从而加重了Cd胁迫对幼苗生长的抑制作用。表明BR通过降低龙葵幼苗的抗氧化能力, 增加了幼苗对Cd毒害的敏感性。Abstract: Cadmium (Cd) is one of the most toxic heavy metals with a strong inhibitory effect on plant growth. Although the effects of auxin on Cd tolerance and accumulation has been reported, the role of brassinosteroid (BR) on Cd stress response has remained unclear. In this study, the physiological effects of BR on Cd stress in Solanum nigrum seedlings were investigated. Cd toxicity induced oxidative damage and decreased the activities of SOD, CAT, and APX in S. nigrum seedlings. Treatment with epibrassinolide (eBL, a synthetic BR) increased Cd sensitivity in S. nigrum seedlings. On the contrary, supplementation with brassinazole (Brz, a specific inhibitor of BR biosynthesis) increased anti-oxidative enzyme activities and reduced reactive oxygen species (ROS) accumulation and oxidative damage. This improved Cd tolerance in S. nigrum seedlings exposed to Cd stress. After treatment with Brz, plant height and root length increased by 29% and 28%, respectively. Also MDA level and Evans blue staining decreased by 37% and 20%, respectively compared with Cd treatment alone. This suggested that BR increased Cd-induced oxidative damage and growth inhibition in S. nigrum seedlings. The results suggest that enhanced Cd sensitivity by BR was correlated with decreasing activities of anti-oxidative capacity in S. nigrum seedling. These results suggested that manipulation of BR level was an effective approach to improve Cd tolerance in plants. It modulated anti-oxidative enzyme activity and ROS accumulation, and provided detailed insights into novel phytoremediation strategies.
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