玉米自交系苗期对高温胁迫的响应机制及其抗逆性

高温胁迫影响夏播玉米自交系幼苗生长、田间整齐度和制种产量,探究玉米幼苗期对温度胁迫的响应机制,有利于培育和筛选抗性优良的品种。该试验选取了浙江大学育成的耐热型和热敏感型自交系各2份,45 ℃进行高温胁迫处理,经高温处理后进行叶绿素含量、抗氧化酶活性测定,以及相关基因表达分析。结果表明,经过高温胁迫处理并恢复生长后,与耐热型自交系相比,热敏感型自交系的叶绿素a、b含量、叶绿素a/b值、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性、过氧化氢酶(CAT)活性、抗坏血酸过氧化物酶(APX)活性、谷胱甘肽还原酶(GR)活性均下降,而脯氨酸含量小幅上升。利用qRT-PCR技术对脯氨酸合成途径的关键酶基因ZmP5CS、降解途径的关键酶基因ZmProDH、热激蛋白基因ZmHSP70和ZmHSP90在高温胁迫条件下的表达特性进行了分析,发现ZmP5CS、ZmHSP70和ZmHSP90明显受热胁迫诱导,并且热敏感型自交系中ZmP5CS、ZmHSP70和ZmHSP90的表达量均显著低于耐热型自交系,而ZmProDH的表达量显著高于耐热型自交系,由此说明,高温胁迫过程中脯氨酸的积累、抗氧化酶活性和热激蛋白基因表达的增强是玉米幼苗耐热性形成的响应机制。

Response mechanism and stress resistance of maize inbred lines to high temperature stress at seedling stage

High temperature stress affects the growth of maize inbred lines during seedling period and field tidiness as well as seed yield, therefore, exploring the response mechanism of maize seedling stage to temperature stress is conducive to breeding and screening varieties with high resistance. The mechanism was studied through the determination of chlorophyll content, antioxidant enzyme activity and gene expression of two different phenotypes after high temperature stress treatment at 45 ℃. The results showed that chlorophyll a and chlorophyll b content, chlorophyll a/b value, SOD activity, POD activity, CAT activity, APX activity and GR activity in heat sensitive inbred lines decreased dramatically compared with heat resistant lines after high temperature challenging and recovery experiment ,while the proline content increased slightly. The expression of ZmP5CS and ZmProDH, two key enzyme genes of proline metabolic pathway, and heat shock protein genes ZmHSP70, ZmHSP90 under high temperature stress were analyzed by qRT-PCR. Our result showed that ZmP5CS, ZmHSP70 and ZmHSP90 were significantly induced by heat stress, and the induction of these genes in heat sensitive inbred lines were mild in comparison with heat resistant inbred lines, while the expression of ZmProDH was significantly higher. These results showed that the accumulation of proline, activity of antioxidant enzymes and expression of heat shock protein genes involved in maize seedlings response to high temperature stress.