Multi-omics Insights into Carbohydrate-active Enzymes and Fruiting Body Differentiation in Leucopaxillus giganteus

Leucopaxillus giganteus is an edible and medicinal macrofungus in China. However, its cultivation remains challenging , and the mechanisms underlying its fruiting body formation are poorly understood. Here, we integrated genomic, transcriptomic, and metabolomic analyses to investigate the roles of carbohydrate-active enzymes (CAZymes) in carbon source utilization and fruiting body development. Using second- and third-generation sequencing, we assembled a 56.80 Mb genome containing 9,717 coding genes, including 4,427 genes related to CAZymes. The CAZyme profile of L. giganteus was rich in plant cell wall (PCW)-degrading enzymes such as GH28, GH31, and CBM1, which are common across saprotrophs. Transcriptome sequencing of four tissues (pileus, lamella, stipe, and mycorrhiza) revealed that cellulose- and hemicellulose-degrading CAZymes (e.g., GH6, GH12) were enriched in fruiting bodies, whereas chitin-degrading CAZymes (e.g., GH18) were enriched in mycorrhizae. These findings confirm the lignocellulose-degrading capacity of L. giganteus. Metabolomic analysis indicated that flavonoids and lipids were abundant in mycorrhizae; esters and alkaloids were abundant in stipes; triterpenoids were abundant in pilei; and aldehydes and carbohydrates were abundant in lamellae. KEGG pathway enrichment analysis indicated that amino sugar and nucleotide sugar metabolism, along with starch and sucrose metabolism, were the dominant carbohydrate metabolism pathways, indicating that glucose was the optimal carbon source for growth. Finally, we identified the roles of carbohydrate metabolism-related genes in regulating fruiting body formation, providing new insights into the growth and developmental mechanisms of L. giganteus.