外源一氧化氮提高白灵侧耳菌丝耐热性生化途径分析

为了探索外源一氧化氮（NO）提高食用菌菌丝体耐热性的生化途径,以白灵侧耳Pleurotus eryngii var. tuoliensis菌株CCMSSC 00489为材料,通过测定高温胁迫下外源添加硝普钠（sodium nitroprusside,SNP,NO供体）后,菌丝体内超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、谷胱甘肽还原酶（GR）和过氧化物酶（POD）等4个抗氧化酶活性的变化,研究外源NO在高温胁迫响应中对抗氧化酶的影响。试验表明,高温胁迫致使菌丝体内TBARS含量升高,膜脂过氧化加剧。在正常温度培养（CK）下,外源添加SNP无显著缓解膜脂过氧化的效果,而高温胁迫条件下缓解效果显著,高温胁迫6h和12h,TBARS含量较对照（未添加）分别下降31.5%和25%。研究表明,抗氧化酶类对外源NO的响应不同。在有外源添加SNP的高温胁迫条件下,菌丝体内的SOD、CAT和GR活性随处理时间的延长而显著增强,在处理72h达到最高,分别是对照（0h）的1.73、7.29和4.95倍。其中CAT是高温胁迫响应的主要抗氧化酶类,其活力可以mmol/L·min^-1·mg^-1 of protein计量,而其他种类的活力均仅以μmol/L·min^-1·mg^-1 of protein计量。在试验条件下,这些抗氧化酶类活性的提高与TBARS含量的降低相呼应,表明外源NO通过提高SOD、CAT、GR的活性降低高温胁迫下的活性氧水平,缓解其氧化损伤,提高菌丝体耐热性。POD活性在外源添加SNP的高温胁迫条件下显著降低。

Biochemical pathway analysis of exogenous NO improving heat-tolerance of Pleurotus eryngii var.tuoliensis

In order to explore the biochemical pathway of exogenous nitric oxide (NO) improving the heat-tolerance of mycelium of mushroom, the effect of exogenous SNP (sodium nitroprusside, a NO donor) on the response of antioxidant enzymes under heat stress was studied through examining activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) as well as peroxidase (POD) in mycelium of Pleurotus eryngii var. tuoliensis (strain CCMSSC 00489). Results showed that heat stress led to the increase of TBARS content, which revealed enhancement of membrane lipid overoxidation. The application of exogenous SNP had significant effect on overoxidation anesis under high temperature while at the normal temperature SNP showed ineffective. Compared with CK (no exogenous SNP added), the content of TBARS in the mycelium treated with exogenous NO decreased by 31.5%, 25% respectively, at 6h and 8h heat treatment. In addition, the antioxidant enzymes in vivo responded differently to exogenous NO. After addition of SNP under heat stress, the activities of SOD, CAT and GR increased significantly as heating duration went on and reached to the maximum in 72h, being respectively equivalent to 1.73, 7.29 and 4.95 times of those of CK (0h). Among the four antioxidant enzymes, CAT played the most important role in response to high temperature stress and its activity was measured by mmol/L·min^-1·mg^-1 of protein while others by μmol/L·min^-1·mg^-1 of protein. Under experimental conditions, the increasement in antioxidant enzymes activities was in accordance of the decrease in TBARS content. In conclusion, the application of SNP could increase the heat-tolerance of the mycelium by improving the activities of SOD, CAT, GR and further mitigating the oxidative damage. The activity of POD decreased under heat stress with exogenous NO application.