A Conserved Lignocellulolytic Secretome with Quantitative Modulation in Leucoagaricus gongylophorus, the Mutualistic...

Leucoagaricus gongylophorus is essential to the mutualistic relationship between leaf-cutting ants and their fungal gardens. Known for its ability to degrade complex plant polysaccharides, this fungus produces a range of CAZymes and FOLymes enzymes that have significant potential for biotechnological applications. We investigated the growth kinetics, enzymatic activities and quantitative secretome modulation of L. gongylophorus grown in submerged cultures containing glucose, carboxymethylcellulose (CMC), xylan or pectin as sole carbon sources. In the comparative analysis, glucose was the preferred carbon source for biomass accumulation reaching 8.6 g L^-1 at day 35, whereas cultures grown on pectin showed limited growth. In the case of enzyme activity, pectin cultures had the highest values in endo-β-1,4-glucanase, pectinase and laccase activities, reaching up to 50.7 U L^-1, 206.6 U L^-1 and 97.3 U L^-1, respectively. In addition, a quantitative proteomic analysis was performed across the different growth conditions and identified 290 proteins, of which 201 were assigned to the secretome. Presence-absence analysis revealed 93 proteins shared across substrates, including 43 consistently detected at both time points, while pectin cultures exhibiting a more diverse set of exclusive secreted proteins. A key difference between conditions was in protein abundance rather in terms of protein profiles, cellulolytic enzymes were preferentially enriched in CMC cultures, pectinolytic enzymes in pectin, and oxidative proteins in xylan-grown cultures. Based on our results, L. gongylophorus adapts to different polysaccharides primarily through quantitative regulation of a shared secretome, reflecting a finely tuned enzymatic strategy that is consistent with its mutualistic lifestyle.