Transcriptional Profiling and Key Enzyme Activity of Epichloë sinensis Isolated from Festuca sinensis in Response to Na2SeO3

Fungal endophytes exhibit symbiotic relationships with their host plants and convert inorganic selenium to organoselenium and Se0. In order to elucidate how Epichloë sinensis from Festuca sinensis adapts to different concentrations of sodium selenate, the dynamic changes of mycelial enzyme activities and metabolic changes at the transcriptional level were documented over a period of 36 h. The activity of enzymes (superoxide dismutase, glutathione reductase, glutathione S-transferase, cysteine synthetase, and methionine synthesis) in mycelia increased in the presence of increased Se concentrations during the cultivation period. The strain with selenium enrichment showed differential changes in gene expression compared to the strain without selenium enrichment, with more changes observed at higher Se concentrations over time. Notably, genes related to ribosomes or ribosome biogenesis in eukaryotes showed significant expression differences among certain groups, with up-regulation of genes involved in oxidoreductase activity, superoxide dismutase, and siderophore biosynthetic processes, and down-regulation of genes involved in steroid biosynthesis. These findings contribute to a better understanding of the transcriptional response of Epichloë sinensis to selenium.