Cellulose degradation in Glenea cantor (Fabricius) (Coleoptera: Cerambycidae): functional characterization of GcEGaseZ7 and Cellulase reveals a novel enzymatic activity.

Glenea cantor (Fabricius) is an important forest pest that mainly attacks kapok trees, breaking down cellulose and lignin through 3 enzyme activities: endoglucanase, filter paper enzyme, and cellobiase. In this study, we unveiled the cloning and expression of 10 endoglucanase genes, GcEGase5A1, GcEGase5A2, GcEGaseZ2, GcEGaseZ3, GcEGaseZ4, GcEGaseZ5, GcEGaseZ7, GcEGaseZ8, GcEGaseZ9, and Cellulase, all of which exhibit enzymatic activities in G. cantor. These findings indicated that Cellulase shares sequence homology with beetle GHF45, whereas the other 9 endoglucanase genes are homologous to beetle GHF5. GcEGaseZ4 presented the highest expression in the foregut. In contrast, GcEGase5A2 and Cellulase presented peak expression in the midgut. Furthermore, GcEGaseZ7 was identified as the most highly expressed endoglucanase in the hindgut. Functional assays confirmed the ability of GcEGaseZ7 and Cellulase to degrade cellulose, and their cellulase activities were 75.57 ± 1.21 U/mg and 344.79 ± 6.91 U/mg, respectively. These results enhance our understanding of the complex cellulase system in insects and provide insights into the efficient digestion of cellulosic materials by wood-consuming insects. This research also has potential applications in bioenergy production and the development of biomaterials from lignocellulosic biomass.