Multi-omics analysis of polysaccharide accumulation and associated metabolic reprogramming across developmental...

Polysaccharides are important bioactive components of Ganoderma tsugae fruiting bodies; however, the developmental dynamics and molecular processes associated with their accumulation remain poorly understood. This study aimed to elucidate polysaccharide-associated metabolic remodeling during fruiting body development under oak-log biomimetic cultivation.

Five developmental stages were examined, including primordia (T1), immature fruiting body (T2), pre-basidiospore discharge (T3), basidiospore discharge (T4), and the end of basidiospore discharge (T5). Crude polysaccharide content was determined, and transcriptomic and untargeted metabolomic analyses were integrated to identify key pathways, genes, and metabolites associated with polysaccharide accumulation. Selected genes were further validated by qRT-PCR.

Crude polysaccharide content increased from T1 to T3, reached a maximum at T3 (0.90 g/100 g), and subsequently declined. A total of 5,676 differentially expressed genes and 911 differentially accumulated metabolites were identified, with clear stage-dependent separation at both transcriptomic and metabolomic levels. Integrated KEGG analysis indicated that starch and sucrose metabolism was the core pathway associated with polysaccharide accumulation, whereas galactose metabolism functioned as a supplementary module contributing to precursor supply and structural diversification. Dynamic expression of FKS1 and multiple glycoside hydrolase-related genes, together with changes in sugar phosphates and disaccharide metabolites, suggested coordinated regulation of substrate degradation, precursor supply, glycan elongation, and carbon redistribution. The qRT-PCR results were consistent with the RNA-seq data.

These findings indicate that polysaccharide accumulation in G. tsugae fruiting bodies is a developmentally coordinated process rather than the result of a single isolated biosynthetic step. The T3 stage appears to represent a key transition point for polysaccharide accumulation and carbon metabolic reprogramming. This study provides a molecular and metabolic framework for understanding polysaccharide accumulation during G. tsugae development and offers potential candidate genes and pathways for future functional validation.