Multiomics and enzyme activity analyses provide insights into polysaccharide biosynthesis in Laetiporus cremeiporus

Polysaccharides are a kind of key bioactive compounds in the macrofungal genus Laetiporus. In this study, Laetiporus cremeiporus, an understudied species endemic to East Asia, was investigated using multiomics and enzymatic activity analyses across four mycelial growth periods. A total of 980 metabolites were identified, of which 14 differentially accumulated metabolites were significantly associated with polysaccharide biosynthesis. The content of these metabolites, including uridine diphosphate glucose, guanosine diphosphate mannose, glucose-6-phosphate, and glucose-1-phosphate, exhibited substantial changes throughout the growth stage reaching peaks on Day7. Transcriptome analysis revealed 12,366 differentially expressed genes. Among these genes, those encoding key enzymes involved in the polysaccharide biosynthesis, such as hexokinase, glucose-6-phosphate isomerase, and phosphoglucomutase (PGM), showed high expression levels on Day1, followed by a general decreasing expression trend. This phenomenon likely supported the rapid initial synthesis of intermediate metabolites, which was then inhibited possibly due to negative feedback. This expression pattern in general corresponded to their enzyme activities. Weighted gene co-expression network analysis identified that two genes encoding PGM were significantly correlated with polysaccharide biosynthesis, and played critical roles in regulating this biosynthesis pathway. In summary, this study provides valuable insights into the polysaccharide biosynthesis of L. cremeiporus, which will benefit the development of polysaccharide-based functional foods from macrofungi.