Integrated Transcriptome and Metabolome Analysis Provides Insights into Blue Light-Mediated Color Formation in Auricularia heimuer

Auricularia heimuer is an economically important edible mushroom, and its black color serves as an important quality indicator. Blue light represents a vital environmental stimulus regulating fungal development and secondary metabolism; however, its association with melanin biosynthesis in A. heimuer remains unclear. In this study, the fruiting bodies of A. heimuer cultivated under full-spectrum light and three blue light intensities (200 lux, 500 lux, and 2000 lux) were used as experimental samples for combined transcriptomic and metabolomic analyses. Results showed that melanin accumulation was correlated with blue light treatment, with the highest melanin content observed under 2000 lux blue light. High-intensity blue light was linked to widespread transcriptional and metabolic reprogramming, significantly enriching the biosynthesis pathways of (1) phenylalanine, tyrosine, and tryptophan, as well as (2) ubiquinone and other terpenoid-quinones. Key genes putatively involved in melanin synthesis, including tyrosinase, laccase, and PKS, were significantly upregulated, accompanied by changes in a putative DOPA-type eumelanin biosynthetic model. This study offers a theoretical reference of the molecular regulatory network linked to blue light and melanin biosynthesis in A. heimuer, providing a theoretical basis for optimizing industrial light cultivation strategies.