钙对苹果果实超氧化物歧化酶、过氧化氢酶活性及其基因表达的影响

Effects of calcium on activities and gene expressions of superoxide dismutase and catalase in apple (Malus pumila Mill.) fruits

采用果实薄片培养试验研究不同钙浓度(0、1和10 mmo1/L CaCl2,5 mmo1/L EGTA)和处理时间(6、12、24和48 h)下苹果果实活性氧代谢特征;运用荧光定量PCR方法分析编码苹果超氧化物歧化酶(SOD)、过氧化氢酶(CAT)基因在分子水平的表达。高钙处理12 h后,SOD酶的活性显著增加,O.2-产生速率显著下降;高钙处理24 h后,CAT酶的活性显著增加,H2O2含量显著下降;缺钙处理下SOD酶和CAT酶的活性受到抑制,O.2-形成速率和H2O2含量显著增加。基因表达实验显示,高钙处理12 h后,SOD基因的表达量增加,与SOD酶活性变化一致,说明SOD酶的活性取决于SOD基因的表达量;高钙处理12 h后,CAT1基因的表达量增加,而CAT酶的活性是在加钙处理24 h后显著增加,说明CAT酶的活性并不完全取决于CAT1基因的表达量,推断其酶活性还取决于该基因翻译后的修饰调控。上述研究表明,苹果外源补钙通过在分子水平上调SOD和CAT1基因表达量来激活SOD和CAT酶的活性,有效减少体内活性氧积累,确保果实生理代谢平衡。

Superoxide dismutase（SOD）,catalase（CAT）,O-·2 and H2O2 in apple（Malus pumila Mill.） fruits were investigated under the hydroponic condition with 0,1,10 mmo1/L CaCl2 and 5 mmo1/L EGTA,and expression patterns of SOD and CAT1 gene were analyzed by real-time PCR.Addition of 10 mmo1/L CaCl2 to the culture solution with 12 h and 24 h exposure significantly improved the activities of SOD and CAT,respectively,and simultaneously decreased O-·2 and H2O2 accumulation.Addition of 5 mmo1/L EGTA,as a specific chelator of Ca,induced O-·2 and H2O2 accumulation correlated with decreases in SOD and CAT activities.The abundance of SOD gene was up-regulated by calcium addition after 12 h exposure in accordance with change of SOD activity,indicating that SOD activity was modified by SOD gene expression.However,expression of CAT1 gene was not in accordance with change of CAT activity.It seemed that CAT activity was modified by CAT1 gene expression particularly at the level of post-translational modification.It was concluded that calcium addition might protect apple fruit tissues against oxidative stress by up-regulating gene expressions and activities of SOD and CAT,then precisely controlling O-·2 and H2O2 accumulation.