Molecular mechanisms of circRNAs in regulating reproductive differentiation and enzymatic activity of Eurotium cristatum

This study investigated the role of circular RNAs (circRNAs) in regulating reproductive differentiation and metabolic activity in Eurotium cristatum, a key fungus involved in dark tea fermentation. Using circRNA sequencing and physiological analyses, we identified 1,818 high-confidence circRNAs, of which 52 were differentially expressed between sexual and asexual mycelia. Source genes of these circRNAs were enriched in oxidative phosphorylation, pyrimidine metabolism, and amino acid biosynthesis pathways. Physiological assays showed that sexual mycelia produced significantly more spores and exhibited higher cellulase, pectinase, protease, and polyphenol oxidase activities than asexual mycelia did. These phenotypic differences were closely associated with distinct circRNA expression patterns, suggesting that circRNAs coordinate sexual development and enzymatic function by modulating energy and metabolic networks. This study provides the first circRNA atlas of E. cristatum, thus offering new insights into its reproductive regulation and potential for industrial applications.