Changes in trehalose content, enzyme activity and gene expression related to trehalose metabolism in Flammulina velutipes under heat shock

Trehalose plays important roles in the protection of organisms against adverse environmental conditions. The growth and development of Flammulina velutipes is regulated and controlled under complex external conditions. This study investigated the effect of heat stress on trehalose metabolism in mycelia and fruiting bodies. The activities of enzymes involved in trehalose metabolism, the transcriptional levels of the corresponding genes and the trehalose content in the mycelia of Flammulina velutipes strain Dan3 under relatively high temperatures were investigated. The mycelia and fruiting bodies of a strain cultivated in a factory were collected at different stages to examine the trehalose content and expression levels of various genes. The results showed that intracellular trehalose significantly accumulated in the mycelia in response to 37 degrees C heat shock. Heat shock significantly stimulated the activities of trehalose-6-phosphate synthase and trehalose-6-phosphate phosphatase, thereby promoting the accumulation of trehalose for the first 2-6 h. The activity of neutral trehalase also decreased during this period. In addition, changes in the activities of trehalose-6-phosphate synthase, trehalose-6-phosphate phosphatase and neutral trehalase paralleled changes in the expression levels of the regulatory genes. As for the trehalose phosphorylase, the degradation of trehalose was stronger than its synthesis under heat stress. Heat shock can induce a stress response in the mycelia through the regulation of genes related to trehalose metabolism and the subsequent promotion and control of the transcription and translation of enzymes. The analysis of the trehalose and gene expression levels in the cultivated strain suggests that a substantial amount of trehalose had accumulated in the mycelia prior to induction of the primordia, and the fruiting bodies could possibly utilize degraded trehalose that translocated from the mycelia to maintain their growth.