Transcriptomic analysis of the dynamic changes in polysaccharide biosynthesis metabolism in Lentinula edodes...

Lentinula edodes, a mushroom valued both nutritionally and medicinally, produces polysaccharides as its principal bioactive compounds, known for their significant pharmacological effects. However, low yields have limited their large-scale industrial application. To address this limitation, the present study conducted a systematic analysis of transcriptional dynamics and identified critical genes and pathways involved in polysaccharide biosynthesis. This study integrated real-time monitoring of polysaccharide production during fermentation with transcriptomic analysis, enabling an initial identification of the key metabolic pathways involved in polysaccharide synthesis in L. edodes. The study revealed that intracellular polysaccharides (IPS) reached a maximum concentration of 0.47 g/L, total polysaccharides (TPS) peaked at 0.97 g/L, and extracellular polysaccharides (EPS) attained 0.56 g/L. Fluctuations in the activities of key enzymes involved in polysaccharide biosynthesis-hexokinase (HK), phosphoglucose isomerase (PGI), phosphoglucomutase (PGM), UDP-glucose dehydrogenase (UGD), and UDP-glucose pyrophosphorylase (UGP) had a marked impact on polysaccharide accumulation. Among these, PGM exhibited the highest activity, reaching 566.14 mg protein/min on day 16, and showed a strong positive correlation with IPS production (r = 0.98). Transcriptomic analysis further identified 5609 differentially expressed genes (DEGs), including 2789 upregulated and 2820 downregulated genes. KEGG pathway enrichment analysis revealed the involvement of multiple metabolic pathways in polysaccharide metabolism in L. edodes. These included starch and sucrose metabolism, glycolysis/gluconeogenesis, the pentose phosphate pathway, galactose metabolism, and the tricarboxylic acid (TCA) cycle. Several key enzymes were identified as central to polysaccharide biosynthesis, notably phosphoglucomutase (PGM), glutamine synthetase (GS), glycogen-branching (GBE), UDP-glucose pyrophosphorylase (UGP), pyruvate kinase (PK), β-1,3-Glucan Synthase (FKS), hexokinase (HK), phosphoglucose isomerase (PGI), 6-phosphogluconate dehydrogenase (6PGDH), transketolase (TKT), UDP-glucose 4-epimerase (GALE), malate dehydrogenase (MDH) and citrate synthase (CS). Collectively, these findings provide new mechanistic insights into the biosynthetic pathways of polysaccharides in L. edodes and establish a theoretical foundation for strategies to improve polysaccharide yield in industrial applications.