Core Carbon Metabolism Response Of Pleurotus Ostreatus To High Temperature Stress

Pleurotus ostreatus known as oyster mushroom,is a common cultivated mushroom in the plastic house in China.Because of the poor environmental control,especially at high temperature,P.ostreatus is greatly affected by the environmental conditions,which often casts the huge economic losses from “spawn-burning”.Thus,it is an important scientific research topic for the response or tolerance of the edible mushroom to high temperature stress.In this study,the cultivar CCMSSC00389 culture was used to explore the core carbon response mechanism of P.ostreatus to high temperature stress.The main results are as follows:1.The metabolomics was used to detect the effect of high temperature stress on the metabolites in mycelia.The results showed that,more than 70 different metabolites were obtained in the mycelia under high temperature stress for 6,12,24,48 h,and these differential metabolites were involved in 32 metabolic pathways.The metabolic pathways in response to high temperature stress included the acceleration of glycolysis and tricarboxylic acid cycle,the enhancement of fatty acid decomposition,the increase of most amino acids,the changes of purine,pyrimidine and vitamin contents,and the outstanding performance of several plant hormones.Among all kinds of metabolites,amino acids continuously changed with heat stress,nucleotides clearly changed with heat stress at 12 h and 48 h,and lipids exhibited an increasing trend with prolonged heat stress,while few kinds of saccharides and vitamins changed under heat stress.2.Lactate as an important differential metabolite under high temperature stress,the effect of its accumulation on the mycelia and the reason for its accumulation under high temperature were investigated.It was determined that lactic acid increased continuously in mycelia under high temperature stress for 48 h with aerobic condition,by using ultra-high performance liquid chromatography.Lactic acid could inhibit the growth of mycelia when the lactic acid with different concentration was added in the medium.The results of measurements of ROS,oxygen consumption rate,ATP production,and mitochondrial copy number revealed that high temperature caused the ROS explosion,decreased the oxygen consumption rate and ATP production in mycelia,which indicating that mitochondrial dysfunction occurred.The content of lactic acid in mycelia decreased significantly when 10 mmol/L glycolysis inhibitor 2-deoxyglucose or 2,6,8 mmol/L ROS scavenger ascorbic acid were added in the medium under high temperature stress,which indicated that the main reason for the accumulation of lactic acid might be the acceleration of glycolysis and the mitochondrial dysfunction under high temperature stress.3.The mechanism of trehalose improving the thermostability of P.ostreatus mycelia through regulating the core carbon metabolic flow was studied.The content of lactic acid in the mycelia,the activity and the transcription of key metabolic enzyme in the core carbon metabolism pathway,the intracellular oxidation state,the oxygen consumption rate and the ATP content were measured,by adding endogenous trehalose with a concentration of 1.5% and by overexpressing of the 6-phosphate trehalose synthetase gene.The results showed that,trehalose can decrease the content of lactate,decrease the expression of the key enzyme genes in glycolysis,alleviate the increase of glycolysis,and can enhance the transcription of g6 pdh and the corresponding enzyme activity in the pentose phosphate pathway under high temperature stress.The enhancement of pentose phosphate pathway will increase the production of NADPH and GSH,and trehalose can also alleviate the decrease of oxygen consumption,improve the synthesis of ATP and restore mitochondrial function,and finally improve the thermostability of mycelia.Conclusion: The basal metabolism response occured in P.ostreatus mycelia under high temperature stress.The accumulation of lactic acid under high temperature stress inhibited the growth of P.ostreatus mycelia.The regulation of core carbon metabolic flow plays a role of directional regulation in alleviating high temperature effects,and the function of mitochondria can affect the mycelial growth and its response to stress.