BABA诱导香蕉果实抗病性与贮藏期活性氧积累的关系

摘要

【目的】研究β-氨基丁酸（BABA）对采后香蕉果实抗病性的诱导作用和贮藏期果皮活性氧含量、抗病相关酶及基因表达量的变化，为探索抗病保鲜新技术提供理论依据。【方法】香蕉果实经5 g·L-1 BABA溶液低压渗透处理，或预先用3.14 mg·L-1的二苯基碘（活性氧合成酶NADPH氧化酶的专一性抑制剂，diphenylene iodonium， DPI）低压渗透，再做BABA溶液低压渗透处理。处理后0、3、6、12、24、48、72 h分别接种2×105个/mL炭疽病菌孢子于果皮上，并测定接种果实在（20±2）℃、85%-95%湿度（RH）下贮藏5-16 d的病斑直径；测定处理24 h后接种果实在（20±2）℃、RH 85%-95%下贮藏期间的超氧阴离子（）含量，过氧化氢酶（CAT）、抗坏血酸过氧化物酶（APX）、β-1,3-葡聚糖酶（GUN）、苯丙氨酸解氨酶（PAL）和几丁质酶（CHI）活性及其基因表达。【结果】处理果实贮藏5 d后，经BABA处理24 h后接种炭疽病菌孢子的果实病斑直径比对照果实的明显减小，表明 BABA 处理需要适当的诱导时间才能产生效果；该 BABA 处理果实在贮藏期间的产生速率和活性氧合成酶MaNOX表达在贮藏5-12 d均明显高于对照；CAT活性和MaCAT表达量分别于贮藏5 d 和1-5 d明显高于对照；APX活性和MaAPX表达量分别在5-8 d、14 d和1-5 d明显高于对照；CHI活性和MaCHI表达量分别在5-12 d和1-5 d高于对照，GUN活性和MaGLU表达量均于8-14 d高于对照，PAL活性和MaPAL1表达量均在12-14 d高于对照；其它时间点差异不大。二苯基碘（活性氧合成酶抑制剂，DPI，3.14 mg·L-1）结合BABA（5 g·L-1）处理香蕉果实抑制了上述BABA处理的效果。【结论】活性氧参与了BABA诱导香蕉抗病性的过程，BABA处理启动了香蕉活性氧的保护机制，包括活性氧水平提高、清除酶活性协同增强和抗病相关蛋白应答等，从而增强了香蕉果实的抗病性。%[Objective]Effects of β-aminobutyric acid (BABA) on diseases-tolerance of harvested banana (Musa AAA Group cv. Brazil) and the possible mechanism were investigated to provide theoretical basis for the new technology of resistant and preservation.[Method] In this study, diphenylene iodonium (DPI), a NADPH oxidase specific inhibitor, was used to inhibit ROS generation in BABA treated fruits. After 5 g·L-1 BABA treatment or 3.14 mg·L-1DPI followed with 5 g·L-1BABA treatment, banana fruits were inoculated withCollectotrichum musae (2× 105 spores/mL) at 0, 3, 6, 12, 24, 48, and 72 h, respectively, and stored at20±2℃ and RH 85%-95%. The disease spot sizes were determined at 5 d to 16 d. The fruit inoculated withC. musae at 24 h after BABA or DPI treatments and stored at (20±2)℃ and RH85%-95%, and the peel was used for determination of production rate, activities of catalase (CAT) and ascorbate peroxidase (APX), β-1, 3-glucanase(GUN), phenylalanine ammonia lyase(PAL), chitinase (CHI), gene expressions ofMaCAT,MaAPX,MaGLU, MaCHI,MaPAL1andMaNOX during storage.[Result] BABA treatment effectively reduced the disease spot sizes on the peel of inoculated banana at 24 h after BABA treatment and cultured for 5 d, showing that BABA treatment needed proper time to have an effect. The production rate andMaNOX gene expression of BABA treated fruits were evidently higher than those of control during 5-12 d storage. Compared with the control, CAT activity andMaCAT expression were higher on day 5 and 1-5 d, respectively. APX activity andMaAPX expression were higher on 5-8 d and 14 d, and 1-5 d, respectively. CHI activity andMaCHI expression was higher on 5-12 d and 1-5 d, respectively. Both of GUN activity and MaGLU expression were higher on 8-14 d. Both PAL activity andMaPAL1 gene expression were higher on 12-14 d . No significant difference was found in other time points. DPI combined with BABA treatment suppressed the above effects of BABA treatment.[Conclusion]These results strongly suggest that reactive oxygen species was involved in the BABA-induced disease tolerance. BABA treatment started the protection mechanism of reactive oxygen species in banana fruits, including the production of reactive oxygen, the increasing of free radical scavenging enzyme activities, and the response of defense-related gene expression.