High temperature-induced oxidization injuries were investigated in wild type (Columbia) and salicylic acid (SA)altering Arabidopsis mutants snc1 with high SA level, transgenic line nahG with low SA level, and npr1 - 1 with SA signaling blockage at controlled conditions. Four-week-old plants were randomly divided into two groups consisting of control plants grown at 22 ℃/18 ℃ light/dark, and high tamperature-stressed plants continuously grown at 38 ℃, respectively. The leaves were harvested after 24 h and 48 h of exposures to the high-temperature (for short "Ht"), and used to analyse the antioxidant capacities. Results showed that 24 h of exposure to Ht increased the activities of superoxide dismutase (SOD) in wild-type plants, while decreased the activities of SOD in snc1 and nahG, and did not affect the activities in npr1 - 1. However, 48 h of exposure to Ht inhibited the SOD activities in all the tested plants, with the most effectiveness being observed in snc1 and nahG plants. The exposure to Ht (24 or 48 h) had no influence on the activities of peroxidase (POD) in wild-type plants, while inereasecl the POD activities in other three mutants, especially significant in snc1 plants. The exposure to Ht (24 or 48 h) dampened the activities of catalase (CAT) in all the analysed plants with a time-dependent manner, and similarly the snc1 plants were affected most markedly relative to other plants tested. In accord with the changes of antioxidative enzymes, the exposure to Ht caused the membrane lipid peroxidation in all the tested plants, as indicated by enhanced levels of malondialdehyde and rates of electrolyte leakage, with the snc 1 and nahG plants being most dramatic. These data suggested that the exposure to 38 ℃ for 24 h or longer caused membrane lipid peroxidation in Arabidopsis plants, which may be associated with the inhibitions of antioxidative enzymes. Furthermore, the high accumulation or deficiency of endogenous salicylic acid may reinforce the high-temperature-induced lipid peroxidation.%以拟南芥野生型(Columbia)及其内源水杨酸高积累突变体snc1、水杨酸缺失的转基因植株nahG和水杨酸信号转导缺失突变体npr-1-1为材料,在实验室控制条件下模拟高温胁迫,比较了抗氧化酶活性以及氧化胁迫症状的变化,以期揭示内源水杨酸水平或信号转导在植物对高温胁迫应答中可能的作用机制.将4周龄的拟南芥植株随机分为对照组和高温胁迫组,前者置于常温(即22℃/18℃,光照/黑暗),后者于高温(38℃恒温)培养箱中培养.分别在高温暴露24 h和48 h后,收集供试植株叶片进行分析.结果表明,高温处理24 h增强了野生型植株的过氧化物歧化酶(SOD)活性,而npr1-1的SOD活性不受影响.snc1和nahG的SOD则明显降低;高温处理48 h降低了所有供试植株的SOD活性,其中snc1和nahG的降幅最大.高温处理24 h或48 h不影响野生型的过氧化物酶(POD)活性,而不同程度地增强了三种突变体的POD活性,尤其以snc1的最明显.过氧化氢酶(CAT)活性则都受到高温的抑制,其中snc1受抑制程度最大.与抗氧化酶活性受抑制相一致的是高温处理提高了所有供试植株细胞膜的脂质过氧化水平和电解质渗透率,其中snc1和nahG植株受影响最大.高温诱导的叶绿素含量降低也表现出相似的趋势.这些数据表明,在38℃高温下暴露24 h以上,内源水杨酸高积累或缺失的拟南芥抗氧化能力比野生型植株受抑制程度更大,因此,氧化伤害症状也更为明显.
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