能量亏缺导致的膜系统区室化功能丧失在冷藏橄榄果实冷害褐变发生中的作用

Chinese olive [Canarium album (Lour.) Raeusch] is an importmant special subtropical fruit in South China. Low temperature storage is the most effective methed for extending the shelf-life and keeing quality of harvested Chinese olive fruit. Whereas, the fruit of Chinese olive belong to chilling-sensitive fruit, which are very susceptible to chilling injury induced-browning of Chinese olive fruit during storage at low temperature. This might seriously affect the appearance quality and commodity value of Chinese olive fruit. However, little information is available on the physiological mechanism of the browning development induced by chilling injury in cold stored-Chinese olive fruit. The objective of this research is to clarify the role of de-compartmentalization of cellular membrane system caused by limited energy availability on chilling injury induced-browning of Chinese olive fruit during cold storage by investigating the changes in energy status, respiratory metabolism, active oxygen metabolism, phenolic metabolism, membrane integrity, the composition and contents of fatty acids and activities of the membrane hydrolysis-related enzymes, the changes of cellular compartmentalization, i.e. polyphenol oxidase (PPO) located in chloroplasts and other plastids, and phenolic substrates located in the vacuole. In addition, the cold stored-Chinese olive fruit treated with uncoupler of oxidative phosphorylation such as 2,4-dinitrophenol (DNP) or treated with exogenous energy substance like ATP are to further confirm the mechanism of energy status regulating the browning development induced by chilling injury via alteration in membrane system function. The results hope to obtain new theory basis in clarifying possible mechanism of the browning development induced by chilling injury in cold stored- Chinese olive fruit.

橄榄是中国南方重要的特色亚热带水果，低温贮藏是延长橄榄果实保鲜期的主要方法，但橄榄是冷敏型果实，在低温贮藏期间容易产生冷害褐变，严重影响橄榄果实的外观品质和商品价值。目前有关冷害所致橄榄果实褐变的生理机制尚不清楚。本课题拟从冷藏橄榄果实冷害褐变发生、组织能量状态变化、呼吸代谢途径改变、活性氧代谢、酚类物质代谢、细胞膜系统组分和功能变化、酶和褐变底物在细胞中区室化功能变化等方面，阐明能量亏缺导致的膜系统区室化功能丧失在冷害所致橄榄果实褐变发生中的作用；同时采用外源氧化磷酸化解耦联剂2,4-二硝基苯酚（DNP）和提供能量ATP来进一步阐明果实能荷状态通过调控膜系统功能变化而调控冷藏橄榄果实冷害褐变发生的生理机制。研究成果可望在阐明冷害所致橄榄果实褐变发生的可能机制方面获得新的理论依据。

低温贮藏是延长橄榄果实保鲜期的主要方法，但橄榄是冷敏型果实，在低温贮藏期间容易产生冷害褐变，严重影响橄榄果实的外观品质和商品价值。目前有关冷害所致橄榄果实褐变的生理机制尚不清楚。研究发现：.1. 与8℃比较，2℃冷藏会促进橄榄果实冷害指数和褐变指数的上升。0.1 mM 2,4-二硝基苯酚（DNP）处理会加速橄榄果实冷害和褐变的发生，而1.6 mM ATP或1.0 mM γ-氨基丁酸（GABA）处理则显著抑制橄榄果实冷害和褐变的发生。.2. 与8℃比较，2℃冷藏会增强橄榄果实糖酵解（EMP）-三羧酸循环（TCA）呼吸途径，但降低磷酸戊糖呼吸途径（PPP）；此外，2℃冷藏会降低橄榄果实质膜、液泡膜、线粒体膜Ca2+-ATPase、H+-ATPase、Mg2+-ATPase等ATP酶活性和能荷值。认为2℃冷藏所致橄榄果实冷害和褐变发生与橄榄果实呼吸代谢途径改变和能量亏缺有关。.3. 与8℃比较，2℃冷藏会降低橄榄果实活性氧清除能力，促进橄榄果实活性氧的产生和积累，从而促进橄榄果实膜脂过氧化作用；此外，2℃冷藏会提高橄榄果实细胞膜脂降解酶（PLD、脂酶、LOX）活性、促进细胞膜磷脂和不饱和脂肪酸的降解，提高橄榄果实PPO和POD活性，降低橄榄果实总酚和类黄酮含量。认为2℃冷藏所致橄榄果实冷害和褐变发生与橄榄果实活性氧代谢失调、破坏细胞膜结构完整性及促进酚类物质的氧化褐变有关。.4. 与8℃比较，2℃冷藏会提高橄榄果实细胞壁降解酶（PE、PG、Cx、β-Gal、XET）活性、加快橄榄果实细胞壁物质降解，从而破坏橄榄果实细胞壁结构的完整性有关。.5. 与8℃比较，2℃冷藏会降低橄榄果实△1-吡咯啉-5-羧酸合成酶（P5CS）和鸟氨酸-D-氨基转移酶（OAT）活性，提高橄榄果实脯氨酸脱氢酶（PDH）活性，降低橄榄果实脯氨酸含量。认为2℃冷藏所致橄榄果实冷害和褐变发生与橄榄果实脯氨酸代谢失调有关。.6. 此外还研究了GABA减轻橄榄果实冷害和褐变发生与能量代谢、呼吸代谢、活性氧代谢、膜脂代谢、酚类物质代谢的关系。 .在上述研究结果基础上，提出能量亏缺导致的膜系统区室化功能丧失在冷藏橄榄果实冷害褐变发生中的作用机制。