INA诱导的香蕉果实抗病性与早期活性氧积累的关系

 研究2,6–二氯异烟酸（INA）对采后香蕉果实抗病性的诱导作用和早期果皮活性氧含量、抗病相关酶活性及基因表达量的变化。结果表明：香蕉果实经0.5 g · L-1 INA处理后0、3、6、12、24 h接种炭疽病菌孢子，贮藏8 d后，INA处理果实的病斑直径比对照果实的明显减小；INA处理果实的H2O2含量和NADPH氧化酶活性分别在6 h和3 ~ 12 h明显高于对照；过氧化氢酶（CAT）活性均明显低于对照，抗坏血酸氧化酶（APX）活性稍低于对照，CAT和APX基因的表达也受到一定的抑制；内切几丁质酶（CHI）活性在0、3、6、12 h高于对照，外切CHI活性在24 h内逐步增加，而对照保持不变；CHI1和CHI2基因的表达在前6 h略高于对照。综上所述，INA诱导采后香蕉果实抗病性增加与其早期活性氧水平及抗病相关酶活性增加有密切关系，由于活性氧合成酶活性增加、清除酶活性减少而产生的高水平活性氧可能作为信号分子启动了抗病应答反应。

Early Changes of Reactive Oxygen Species in 2,6-dichloroisonicotianic Acid Inducing Tolerance in Postharvest Banana Fruits

2,6-dichloroisonicotinic acid（INA） induces plant tolerance to a wide spectrum of diseases. But whether the compound induced the deseases-tolerance in postharvest fruits and vegetables remains to be clarified. We investigated the effects of INA on diseases-tolerance in harvested banana（Musa AAA Group‘Brazil’）and the possible mechanism. The results showed that INA treatment effectively reduced the disease spot sizes on the peel of banana fruit when inoculated with spore suspension of Collectotrichum musae during 24 h after INA treatment and cultured for 8 d. H2O2，a type of reactive oxygen species（ROS），and the involved enzymes were analysed and it was found that the content of H2O2 and activity of NADPH oxidase，an enzyme catalyze the production of ROS，were stimulated at 3 h，6 h and 12 h after INA treatment，respectively. In addition，INA treatment decreased CAT and APX activities obviously，and suppressed the both genes expression to a certain extent. We also analysed the defence enzyme of chitinase（CHI）and found that activity of intro-CHI and extro-CHI were enhanced at 0–12 h and 0–24 h after INA treatment，espectively，and the expression of CHI1 and CHI2 genes were enhanced lightly at 3–6 h and 0–3 h after INA treatment，respectively. These results strongly suggest that elevated H₂O₂ levels，resulting from enhanced NADPH oxidase activity and suppressed CAT and APX activities，and the enhanced CHI activity are involved in the INA-induced disease tolerance.