Studies On The Metabolic Regulation Of Trehalose In Pleurotus Ostreatus And Pleurotus Pulmonarius Thermal Response

In microorganisms, trehalose functions both as a reserve carbohydrate and as a stress metabolite.Trehalose accumulation is a crucial defense mechanism that stabilizes proteins and biologicalmembranes during periods of stress. The research focus on the role of trehalose in the abiotic stressresistance responses has attracted more and more attentions.The productions of mushrooms in China are always conducted in the traditional mushroom tents,which makes the mushroom vulnerable to climate fluctuations. Sudden change of high temperatureclimate would inhibit the mycelium growth, impair fruiting, and finally affect the quality of mushroom.Oxidative stress triggered by heat stress is the main reason that leads to the damage. Therefore, in-depthstudy of the thermal response mechanisms would provide a theoretical basis for high yield and highquality of mushroom.We investigated the alleviative effects of exogenous trehalose on heat-induced oxidative stress invarious sensitive strains of Pleurotus ostreatus and Pleurotus pulmonarius, which are the maincultivated species of Pleurotus. The responses of trehalose metabolism at the level of enzyme activityand gene expression during heat stress and the recovery period in the two different sensitive type strainsof P. pulmonarius were also studied. Our conclusions were as follows:Under heat stress (at12℃above optimum growth temperature), exogenous trehalose effectedsimilarly on physiological indexes of resistance to oxidative damage between P. ostreatus and P.pulmonarius. Exogenous trehalose could alleviate the oxidative damage induced by heat stress byreducing the generation rate of O-2and H2O2, the activity of LOX and the content of TBARS.Additionally, exogenous trehalose had much different effects on the activities of enzymetic antioxidants,including the positive effect on the activity of antioxidants SOD, the negative effect on enzymeticantioxidants including CAT, APX and GR, and no effect on enzymetic antioxidants POD under the heatstress. The reason for improved heat resistance was that the exogenous trehalose protected SOD activityand scavenged H2O2and O-2. The protective effect was related to trehalose concentration, and the effecton the heat sensitive strains was higher than that on heat resistant strains.Under normal physiological conditions, the in vivo trehalose content in the heat sensitive strain andthe heat tolerant strain did not show a significant difference. An interesting phenomenon is that thetrehalose content increased first and then decreased finally. The increased extent of activities oftrehalose-6-phosphate synthase (TPS) and trehalose phosphorylase (TP) in the direction of trehalosesynthesis in heat sensitive strain was higher than that in heat tolerant strain during the early stress period.TreP pathway and OtsA-OtsB pathway was the main pathway at the early heat stress. In later stressperiod, neutral trehalase and TP were involved in trehalose degradation in two strains. Meanwhile, theTPS activity increased continuously in heat sensitive strain, while reduced in heat tolerant strain.The trehalose content of P. pulmonarius strains rapidly decreased to the control level under heatstress recovery conditions and the decreasing rate in heat sensitive strain were faster than that in heat tolerant strain. But, the TPS activity increased continuously in heat sensitive strain, and TPP was arestriction enzyme in the OtsA-OtsB pathway. Neutral trehalase and TP were involved in trehalosedegradation in two P. pulmonarius strains under heat stress recovery conditions.Analysis of trehalose metabolism-related gene expression during the heat stress and recoverycondition suggests that, in contrast with the case of TPS, TPP and TP, NTH activity was depressedduring heat stress, even though the mRNA of the nth gene increased. The trehalose stress response toheat was presumed to be regulated at the transcription and the translation levels. The response ofmetabolic pathway of trehalose in different sensitive P. pulmonarius strains to heat stress and recoverywere not exactly the same, and that was mainly caused by the mRNA expression of the tps gene.