Plant cell wall-degrading enzymes in weevils
Weevils, part of the Curculionoidea superfamily, are mostly herbivorous beetles, but some are associated with wood-decaying fungi, and a few even hunt other insects. With 62,000 described species, weevils are a major group of plant-eating animals, including economically important pests like bark beetles (Scolytinae). Previous research suggests that enzymes breaking down plant cell wall polysaccharides may have influenced weevil diversification. However, our understanding of the distribution of plant cell wall-degrading enzymes (PCWDEs) and their evolution in Curculionoidea is limited to a few species, primarily within Curculionidae. To fill this knowledge gap, we analyzed PCWDE-encoding genes in 48 weevil species, using transcriptome and genome data. We specifically generated transcriptome data for 21 unstudied species. These species spanned the majority of families within Curculionoidea. Our investigation revealed the presence of 13 families of PCWDEs, many of which consisted of multiple paralogous genes. Different weevil species possessed varying numbers of PCWDE families, ranging from one to nine. Notably, species associated with wood-decaying fungi, including ambrosia beetles (Scolytinae), exhibited a reduced set of PCWDEs compared to closely related species that primarily feed on plants. Furthermore, our study unveiled the presence of endo-a-1,5-L-arabinanases from subfamily 6 of glycoside hydrolase family 43 (GH43_6) in animals for the first time. Our research significantly expands current knowledge on the evolution of PCWDEs in this major group of plant-eating insects. By analyzing a diverse range of weevil species, including previously unstudied ones, we provide valuable insights into the distribution and diversity of these crucial enzymes within Curculionoidea.