Transcriptome and metabolome analyses reveal insights into the response of Morchella sextelata mycelia to lethal heat stress

Driven by a vast consumer market worldwide, Morchella has become a highly popular species for commercial cultivation. In recent years, the scale of their facility-based cultivation has expanded significantly in China. As is known, high temperature is a pivotal environmental factor infecting mycelia activity and fruiting, and severe heat stress may be lethal to Morchella. To excavate the molecular events of Morchella mycelia responding to lethal heat, we analyzed the metabolome and transcriptome of M. sextelata mycelia treated at 40 ℃ for 6 h compared to 23 ℃. Some heat-responsive metabolites related to tyrosine metabolism, pyrimidine metabolism and amino acids biosynthesis were upregulated in the heat shocked mycelia. The levels of antioxidant metabolites, such as caryophyllene and arbutin, exhibited significant alterations. Besides, 5795 differentially expressed genes (DEGs) were identified, which were primarily enriched to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of Two-component system (TCS), ribosome and protein processing in endoplasmic reticulum (ER). Correlation analysis revealed disordered lipid regulatory networks. The enhancement of phospholipid synthesis and the repression of fatty acid desaturation led to the excessive accumulation of phosphatidylcholine (PC) and lysophosphatidylcholine (LPC), probably resulting in irreversible membrane damage and cellular dysfunction under lethal heat stress. This study provided an expanded molecular network for understanding the heat tolerance limits in Morchella and potentially other macrofungi, thereby identifying promising targets for future genetic improvement and cultivation management.