低氧调控金针菇木质化品质劣变分子机制研究

Postharvest rapid senescence of Flammulina velutipes is a serious problem restricting the development of its industry. During the postharvest storage of F. velutipes, the texture of stipe becoming rough, leathery, juiceless and indigestible is an important deterioration performance, which has not been received much attention and research. In our previous study, we found that the senescence process of F. velutipes was accompanied with the lignification caused by the accumulation of lignin and chitin in stipes, and, moreover, low oxygen was proved to be effective in delaying lignification process. However, F. velutipes is of fungi, which is different from plant fruit and vegetable, the mechanism of molecular regulation underlying this is still unclear. This project will be carried out according to point of view “Low oxygen treatment→Regulating lignification metabolic pathways→Inducing lignin and chitin accumulation→Influencing cell morphology→Increasing lignification deterioration of stipe”, and firstly analyze the impact of low oxygen treatment on the material composition, cell microstructure, and texture quality, and make clear the relationship among them during the development of lignification. Proteomics, transcriptomics, metabonomics, and bioinformatics analysis will be employed to elucidate the network of lignification metabolic pathway regulated by low oxygen. Based on the gene expression analysis of lignification related phenylpropanoid metabolic pathway and chitin metabolic pathway, the target of low oxygen inhibiting F. velutipes lignification will be illuminated. This project will provide a theoretical basis and technical strategy for quality deterioration control of postharvest F. velutipes.

金针菇采后快速衰老是制约其产业发展的瓶颈问题，菌柄质地变柔韧、粗糙少汁、塞牙且难消化是金针菇贮藏过程中的一个重要品质劣变问题，但一直未得到重视和研究，我们前期研究发现，金针菇质构品质变化与菌柄中几丁质和木质素积累引起的木质化密切相关，且低氧处理能够显著延缓该木质化进程，但金针菇作为不同于植物源果蔬的真菌类，低氧对其木质化调控分子机制仍不明确。本项目拟从“低氧处理→调控木质化代谢途径→诱导几丁质与木质素积累→影响细胞形态变化→控制菌柄木质化劣变”角度出发，分析金针菇木质化劣变过程中“物质成分基础—亚细胞微观结构—宏观质构品质”三者的变化关系，利用多组学和生物信息学分析探究低氧处理对金针菇木质化劣变代谢途径的调控网络，并通过分析金针菇木质化相关的苯丙烷类代谢途径和几丁质代谢途径相关基因表达，揭示低氧处理抑制金针菇木质化劣变的调控靶标及作用机制，为金针菇采后的品质劣变控制提供理论依据和技术策略。

金针菇采后快速衰老是制约其产业发展的瓶颈问题，菌柄质地变柔韧、粗糙少汁、塞牙且难消化是金针菇贮藏过程中的一个重要品质劣变问题，我们前期研究发现，金针菇质构品质变化与菌柄中几丁质和木质素积累引起的木质化密切相关，且低氧处理能够显著延缓该木质化进程，但低氧对其木质化调控分子机制仍不明确。本项目从“低氧处理→调控木质化代谢途径→降低木质素积累→影响细胞形态变化→控制菌柄木质化劣变”角度出发，分析金针菇木质化劣变过程中“物质成分基础—亚细胞微观结构—宏观质构品质”三者的变化关系，利用多组学分析探究低氧处理对金针菇木质化劣变代谢途径的调控网络。.（1）低氧纳米包装通过抑制苯丙烷代谢途径中PAL、C4H及4-CL活性的增加，降低了金针菇中木质素的积累，较好地维持金针菇的感官品质和微观结构；此外，低氧纳米包装能够维持较高的硫化氢含量，减少了金针菇线粒体中活性氧和Ca2+的累积，抑制了Dnase、Rnase和Caspase-3活性的增加，从而延缓了细胞程序性死亡的进程，最终抑制了金针菇中木质素的积累。.（2）阐明了低氧纳米包装通过抑制金针菇采后呼吸作用、增强了ATP酶活性、提高PPP途径中关键酶NADK和G-6-PDH活性，减少了ROS损害并维持离子平衡，保持了线粒体结构完整性，为机体提供了足够的ATP并维持较高的能荷。同时提高了氧化磷酸化中的关键酶基因NAD1、COX1和ATP8的表达，抑制caspase-1酶活性以及细胞色素c含量的增加，从而延缓金针菇的采后衰老，明确了低氧调控金针菇木质化代谢的靶向位点。 .（3）通过转录组学及分子生物学解析了与木质化相关的基因功能和调控机制，通过诱导木质素酶H2相关基因（GLG4）的差异表达，促进木质素降解；通过降低苯丙烷代谢途径中SPAC16E8.04c的表达，减少了木质素前体L-苯丙氨酸的合成，进而抑制了金针菇中木质素的累积。此外，低氧纳米包装通过调控msp2和RBOHF基因的表达，减少线粒体中细胞色素C的释放，最终延缓了PCD进程，参与调控了金针菇采后木质化劣变的代谢途径。