脱落酸处理对苹果成熟、乙烯合成及其信号转导基因表达的影响

为研究脱落酸（abscisic acid，ABA）对苹果果实采后成熟、乙烯合成及其信号转导基因表达的影响，本实验以‘Granny Smith’苹果果实为实验材料，将其进行外源ABA处理后置于20 ℃贮藏（以无菌水处理为对照），测定贮藏过程中的硬度、可滴定酸质量分数、纤维素酶活力、果胶甲酯酶活力、叶绿素含量、内源ABA含量、乙烯产生速率及乙烯生物合成基因（ACO1、ACO2、ACS1、ACS3）、苹果乙烯信号转导基因（ERS1、ERS2、ETR2、ERF3、ERF4、ERF5）的表达量。结果表明，与对照组相比，ABA处理能降低苹果果实贮藏过程中的硬度和可滴定酸质量分数，提高果实中的纤维素酶和果胶甲酯酶活性，促进叶绿素a、叶绿素b和总叶绿素含量降低。定量聚合酶链式反应分析结果表明，与对照组相比，ABA处理能够显著提高苹果乙烯生物合成基因的表达量（P＜0.05）。同时，参与苹果乙烯信号转导的ERS2、ETR2和ERF3、ERF4、ERF5表达量随着果实采后成熟明显增加，并且ABA处理组果实中的表达量总体显著高于对照组（P＜0.05）。综上，外源ABA处理能够促进苹果内源ABA的合成，提高苹果乙烯生物合基因和信号转导基因的表达，促进苹果内源乙烯合成和乙烯信号的转导，加快苹果果实的采后成熟进程。

Effect of Abscisic Acid Treatment on Apple Fruit Ripening and Expression of Genes Related to Ethylene Biosynthesis and Ethylene Signal Transduction

In order to study the effect of postharvest treatment with abscisic acid (ABA) on apple ripening and the expression of genes related to ethylene biosynthesis and ethylene signal transduction, ‘Granny Smith’ apple fruit were treated with ABA or sterile water as a control and stored at 20 ℃. Fruit firmness, titritable acid content, cellulase activity, pectin methylesterase (PME) activity, chlorophyll content, endogenous ABA content, ethylene production rate, and the expression of genes related to ethylene biosynthesis (ACO1, ACO2, ACS1 and ACS3) and ethylene signal transduction (ERS1, ERS2, ETR2, ERF3, ERF4 and ERF5) were measured. It was found that relative to the control group, ABA decreased fruit firmness and titratable acid content, increased cellulase and PME activities, and promoted the decrease in the contents of chlorophyll a, chlorophyll b and total chlorophyll during storage. Quantitative polymerase chain reaction (q-PCR) results showed that ABA treatment significantly increased the expression of ethylene biosynthesis-related genes (P < 0.05). The expression levels of ERS2, ETR2 and ERF3/4/5 significantly increased during apple postharvest ripening, and they were significantly higher in ABA-treated fruit than in the control group (P < 0.05). Taken together, exogenous ABA treatment promoted the biosynthesis of endogenous ABA in apple fruit, and increased the expression of genes involved in ethylene biosynthesis and signal transduction, thus accelerating the postharvest ripening process.