能量亏缺在Phomopsis longanae Chi.侵染所致采后龙眼果实果肉自溶发生中的作用

Longan (Dimocarpus longan Lour.) fruits are very susceptible to aril breakdown, and postharvest aril breakdown is the most important factors degrading the quality and commodity value, which is the key factor impeding long-distance distribution and marketing of the fruits. However, little information is available on the physiological and biochemical mechanisms of the aril breakdown development in harvested longan fruits. Our previous research showed the development of aril breakdown in harvested longan fruits was related to pathogen infection. Phomopsis longanae Chi is the major pathogens causing aril breakdown in harvested longan fruits. The objectives of this research were to clarify the roles of the limited energy availability on aril breakdown development in Phomopsis longanae Chi-inoculated longan fruits by investigating the changes in energy status, respiratory metabolism, active oxygen metabolism, membrane integrity, the composition and contents of fatty acids and activities of the membrane hydrolysis-related enzymes, the changes of disease resistive material and the activities of disease resistance-related enzymes, the metabolism of cell wall materials, during the development of aril breakdown in Phomopsis longanae Chi-inoculated longan fruits. Meanwhile, longan fruits treated with ATP or inhibitor of respiration such as 2,4-dinitrophenol (DNP) were to further confirm the mechanisms of energy status regulating the development of aril breakdown in Phomopsis longanae Chi-inoculated longan fruits. The research results hope to obtain new theory basis in clarifying possible mechanism of aril breakdown development in harvested longan fruit caused by pathogen infection.

果肉自溶是采后龙眼败坏的主要原因之一，严重影响其使用品质和商品价值，是限制龙眼果实长期贮运的关键因素。目前对龙眼果实采后果肉自溶的生理生化机制所知甚少。我们前期的研究认为，龙眼采后果肉自溶与病原菌的侵染有关，其中龙眼拟茎点霉（Phomopsis longanae Chi.）是引起龙眼果实采后果肉自溶最主要的病原菌。本课题拟从P. longanae侵染后龙眼果肉自溶发生、组织能量状态变化、呼吸代谢、活性氧代谢、细胞膜系统组分和功能变化、抗病物质代谢、细胞壁代谢等方面，阐明能量亏缺在P. longana侵染所致龙眼果实采后果肉自溶发生中的作用；同时采用外源呼吸解偶联剂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调控P. longana侵染所致龙眼果实采后果肉自溶发生的机理。研究成果可望在阐明病原菌侵染所致龙眼果实采后果肉自溶发生的可能机制方面获得新的理论依据。

果肉自溶是采后龙眼败坏的主要原因之一，严重影响其食用品质和商品价值，是限制龙眼果实长期贮运的关键因素。目前对龙眼果实采后果肉自溶的生理生化机制所知甚少。我们前期的研究认为，龙眼采后果肉自溶与病原菌的侵染有关，其中龙眼拟茎点霉（Phomopsis longanae Chi.）是引起龙眼果实采后果肉自溶最主要的病原菌。研究发现：.1. P. longanae侵染所致龙眼果肉ATP含量和能荷值下降是龙眼果实采后果肉自溶发生的关键因素。2,4-二硝基苯酚（DNP）促进采后龙眼果肉自溶发生，而ATP则抑制采后龙眼果肉自溶发生。.2. P. longanae侵染所致龙眼果肉自溶发生与P. longanae侵染降低龙眼果肉质膜、液泡膜、线粒体膜Ca2+-ATPase、H+-ATPase、Mg2+-ATPase等ATP酶活性和能荷值，从而促进龙眼果肉能量亏缺有关。.3. P. longanae侵染所致龙眼果肉自溶发生与P. longanae侵染增强龙眼果肉糖酵解（EMP）-三羧酸循环（TCA）呼吸途径，但降低磷酸戊糖呼吸途径（PPP）有关。.4. P. longanae侵染所致龙眼果肉自溶发生与P. longanae侵染降低龙眼果肉活性氧清除能力，促进龙眼果肉活性氧的产生和积累，从而促进龙眼果肉膜脂过氧化作用有关。.5. P. longanae侵染所致龙眼果肉自溶发生与P.longanae侵染提高龙眼果肉细胞膜脂降解酶（PLD、脂酶、LOX）活性、促进细胞膜磷脂和不饱和脂肪酸的降解，从而破坏龙眼果肉细胞膜结构的完整性有关。.6. P. longanae侵染所致龙眼果肉自溶发生与P. longanae侵染提高龙眼果肉细胞壁降解酶（PE、PG、Cx、β-Gal、XET）活性、加快龙眼果肉细胞壁物质降解，从而破坏龙眼果肉细胞壁结构的完整性有关。.7. P. longanae侵染所致龙眼果肉自溶发生与P. longanae侵染降低龙眼果肉抗病物质代谢相关酶（PAL、POD、CHI、GLU、CAD、C4H、4-CL）活性和抗病物质（木质素、类黄酮、总酚）含量、从而降低龙眼果肉抗病性有关。.在上述研究结果基础上，提出能量亏缺在P. longanae侵染所致龙眼果实采后果肉自溶发生中的作用，及DNP和ATP调控P. longanae侵染所致龙眼果实采后果肉自溶发生的可能机理。