Comparative transcriptome analysis reveals the global molecular mechanism of polysaccharide biosynthesis in lentinula edodes mycelium cultured with hemicellulose

Lentinula edodes, whose polysaccharide displays diverse bioactivity, is widely cultivated and consumed in Asia, and commonly grows on hardwood sawdust composed of hemicellulose, lignin and cellulose. Previously, it was found that as the carbon source of L. edodes, hemicellulose significantly promoted polysaccharide production. In order to further investigate the underlying molecular mechanism, high-throughput RNA-seq analysis was performed with glucose-grown and hemicellulose-grown mycelia in this study. A total of 75535 transcripts and 11525 unigenes were harvested, with 85.12% of them successfully annotation and classification according to six public databases. Further, a total of 1203 differentially expressed genes (DEGs) were identified at the transcription level, with 550 upregulated genes and 653 downregulated genes on the hemicellulose supplemented medium, indicating that a series of metabolic pathways were activated in hemicellulose-grown condition. Based on the predicted functions and involved metabolic pathways obtained from GO and KEGG enrichment analysis, DEGs were found to be enriched in signaling transduction, osmotic stress adaptation, as well as carbohydrate metabolism pathways significantly. Therefore, a putative pathway was mapped accordingly for polysaccharide biosynthesis and carbon source catabolism in L. edodes. Moreover, the expression level of pgm was elevated steadily in the 12-hour time frame, indicating the occurrence of polysaccharide biosynthesis continued. In summary, the present study facilitated the discovery of polysaccharide synthesis in L. edodes as well as other Basidiomycetes and provided new insights into efficient cultivation of edible fungi.