基于线粒体结构和功能的外源草酸缓解采后芒果冷害机制

Chilling sensitive fruits are susceptible to chilling injury during storage at low temperature, which result in extremely decrease in storage period and fruit quality. Oxalic acid could not only effectively delay the ripening process in postharvest fruits, but also could alleviate chilling injury in chilling-storage fruits, which has attracted great attention in the studies of fruit storage and keeping fresh. However, the mechanism of oxalic acid alleviating chilling injury in postharvest fruits is still not clear. Preliminary study found that chilling injury in fruits was associated with keeping higher energy status. Mitochondria are an important place generating cellular energy, and the structure and function of mitochondria in fruits was involved in chilling injury under adversity stress. In order to further study the mechanism of oxalic acid alleviating chilling injury in postharvest fruits, mango as experimental material, the effect of oxalic acid.on the stucture, prtotein, fatty acid and mitochondrial electron transport chain were study in this research, which was conductive to illuminating the mechanism of oxalic acid allevating chilling injury of postharvest mango fruits from the perspective of mitochondria strucure and function. These study could provide fundamental basis for controlling chilling injury in postharvest mango fruit and prolonging fresh-storage period. Therefore, this research has both important theoretical and applied values.

冷敏型果实低温贮藏极易发生冷害，导致其品质劣变并缩短贮藏期。目前，草酸在果实贮藏保鲜中的作用已引起极大关注，草酸不仅能有效延缓采后果实成熟，而且能缓解低温胁迫下采后果实冷害的发生，但草酸缓解采后果实冷害的机制仍不清楚。前期研究发现草酸缓解采后芒果果实冷害与其维持较高的能量水平有关。线粒体是能量产生的重要场所，逆境胁迫下果实线粒体结构和功能与采后果实的冷害密切相关。为进一步从线粒体结构和功能角度阐明草酸缓解采后果实冷害机制，本研究以冷敏型果实芒果为试验材料，通过研究草酸处理对低温胁迫下采后芒果果实线粒体结构、线粒体蛋白质、线粒体脂肪酸、线粒体电子传递链的影响，进一步从线粒体结构和功能角度揭示草酸缓解采后芒果果实冷害机制，本研究可为控制采后芒果果实冷害、延长果实贮藏期提供理论一定的理论依据和技术支持。因此，本研究具有重要的理论意义和应用价值。

芒果在低温贮藏时极易发生冷害，草酸处理能缓解芒果冷害的发生。本项目主要研究了草酸处理减轻芒果冷害的发生与芒果线粒体结构和功能的关系。主要结果如下：.1、草酸处理能减轻采后芒果冷害发生，通过显著抑制芒果原果胶和纤维素下降，显著提高水溶性果胶含量，显著提高PG、β-Gal、Cx、PME细胞壁降解酶活性，使芒果能够正常后熟软化，维持果实正常的细胞壁代谢。.2、草酸处理能提高贮藏后期芒果果实线粒体SOD、POD酶活性、提高Vc和GSH含量而显著降低芒果线粒体中活性氧的积累，减轻芒果线粒体膜脂过氧化损伤，减轻冷害发生。.3、电镜观察结果显示，低温贮藏35 d后对照组线粒体内出现大空泡，双层膜结构模糊，而草酸处理组粒体内出现小空泡，双层膜结构仍清晰可见，说明草酸处理能维持低温贮藏中芒果果实线粒体结构的完整，减轻线粒体损伤程度。.4、草酸处理能显著提高芒果线粒体中亚油酸、亚麻酸的含量，保持芒果线粒体膜脂不饱和脂肪酸比例，减轻不饱和脂肪酸含量下降，维持芒果果实线粒体膜流动性和完整性，降低芒果冷害程度。.5、草酸处理能显著提高芒果线粒体复合体II、III、IV活性，显著提高AOX1a、AOX1b、AOX1c和UCP基因相对表达量，同时能显著提高芒果低温贮藏下柠檬酸合酶、异柠檬酸脱氢酶、琥珀酸脱氢酶活性，表明草酸处理可以通过维持芒果果实细胞能量平衡和线粒体正常生理功能来减轻芒果果实冷害发生。.6、蛋白质组学分析研究发现，草酸处理后芒果果实中共筛选出1596个差异蛋白，其中110个下调蛋白，102个上调蛋白，这些差异表达蛋白主要集中在能量代谢、苯丙烷代谢、活性氧代谢等方面。.7、草酸处理组和对照组芒果果实差异表达基因的转录组分析，可以得到草酸处理缓解芒果果实冷害与次生代谢、能量代谢、信号转导等密切相关。