呼吸代谢介导鸡腿菇采后自溶发生机制的研究

Coprinus comatus is popular due to the rich nutrition, delicious taste and high activities such as hypoglycemic action and immune-modulatory. However, C. comatus is one of the mushrooms with very short storage period, and the fruiting body is easy cap-opening, browning and autolysis after harvest. These changes involving complex physiological metabolic reactions are not only the result of programmed development of genetics, but also a passive process to postharvest conditions. In this project, the change on respiratory metabolism and its effect on reactive oxygen metabolism and cell wall metabolism in postharvest fruiting body of C. comatus will be firstly analyzed to exhibit the physiological metabolism characteristics during the storage. The relationship among respiratory metabolism, reactive oxygen metabolism and cell wall metabolism will also be investigated to elucidate the enzymatic and non enzymatic cell wall degradation mechanism in postharvest fruiting body of C. comatus. To insight into the molecular mechanism on the triggering changes of postharvest respiratory metabolism and reactive oxygen metabolism, and cell wall degradation, proteomics research will be performed by iTRAQ-MS/MS proteome analysis and bioinformatics technology. Therefore, the possible autolysis mechanism in postharvest fruiting body of C. comatus will be elucidated. The results of this project will provide fundamental basis and scientific guidance for regulating postharvest autolysis and extending shelf life of C. comatus fruiting body. The results will also serve as a reference for the postharvest regulation of other mushrooms, and promote the development of edible fungi industry.

鸡腿菇（Coprinus comatus）营养丰富，味道鲜美，并具有降血糖、提高免疫等生物活性，深受消费者喜爱。但是鸡腿菇是最不耐贮藏的食用菌之一，采后极易开伞、褐变、自溶，这些变化不仅是遗传学程序化发育的结果，也是响应采后条件的被动过程，涉及生理代谢上的复杂反应。本项目拟研究鸡腿菇采后贮藏过程中呼吸代谢的变化及其介导活性氧代谢、细胞壁代谢的作用，揭示鸡腿菇应对采后条件的生理代谢特征，阐明细胞壁降解的酶促和非酶促机制；iTRAQ-MS/MS技术分析鸡腿菇采后不同时期的蛋白质组，生物信息学方法进行蛋白质功能注释、分类和代谢途径分析，筛选与鉴定差异表达蛋白，结合实时荧光定量PCR探明采后呼吸代谢、活性氧代谢变化及细胞壁降解发生的分子机制与内在联系，揭示自溶发生的可能机理，为调控鸡腿菇采后自溶、延长货架期提供理论基础和科学指导，也可为其它食用菌的采后调控提供借鉴，促进食用菌产业的发展。

鸡腿菇（Coprinus comatus）是食用菌中最不耐贮藏的品种之一，采后极易开伞、褐变、自溶。为探明品质劣变机理，本项目分析了不同贮藏条件下鸡腿菇呼吸代谢、活性氧代谢、细胞壁代谢及蛋白质组的变化，结果表明：（1）异硫氰酸烯丙酯（AITC）可显著（P<0.05）抑制鸡腿菇的呼吸速率；与对照相比，10μL/L的AITC可降低菇体内黄嘌呤氧化酶活性（P<0.05），并在贮藏中后期显著提高琥珀酸脱氢酶、Ca2+-ATP酶以及抗氧化酶（谷胱甘肽还原酶、超氧化物歧化酶、过氧化氢酶等）的活性（P<0.05），降低活性氧（ROS）的积累。（2）鸡腿菇贮藏过程中葡聚糖含量持续下降，几丁质、纤维素含量则是先上升后下降；4 ℃和8 ℃条件下细胞壁代谢酶（纤维素酶、葡聚糖酶、几丁质酶等）活性先升高后下降，峰值出现在第6天或第9天；随着贮藏时间的增加，鸡腿菇多糖的分子量会不断下降，且单糖组成、糖苷键、微观结构会发生改变；近冰温（-0.7 ℃）条件可降低鸡腿菇体内细胞壁代谢和ROS代谢的水平，在第15天时，几丁质含量分别是4 ℃和8 ℃条件下的1.34和1.68倍，而葡聚糖含量则是其他两组的1.21和1.47倍，并且可延缓鸡腿菇多糖结构的改变。（3）分别比较贮藏8天/0天、贮藏16天/0天的鸡腿菇蛋白质组，共有168种差异富集蛋白（DAP）重叠，其中74种DAP上调，86种DAP下调，这些DAP主要参与核糖体、糖酵解、柠檬酸循环和谷氨酸代谢。鸡腿菇采后贮藏过程中，开伞之前，受核糖体调控的碳水化合物代谢（包括细胞壁水解和能量生物合成）参与了蘑菇自溶；而开伞之后，自溶与ROS的累积和活化丝裂原活化蛋白激酶（MAPK）信号通路有关。项目揭示了鸡腿菇采后贮藏过程中的生物学过程以及自溶发生的可能机理，可为鸡腿菇采后保鲜技术开发提供理论基础，并为其它食用菌的采后品质保持提供借鉴，促进食用菌产业的发展。