Wood-boring larvae of longhorned beetles (Coleoptera; Cerambycidae) have evolved a diverse array of plant cell wall degrading enzymes.

Longhorned beetles (Cerambycidae) are the most diverse group of wood-feeding (xylophagous) insects on Earth. Their larvae feed on woody tissues made up of large amounts of plant cell wall (PCW), which is notoriously recalcitrant to breakdown. To efficiently access nutrients from their food source, cerambycid larvae have to deconstruct PCW polysaccharides - like cellulose, hemicelluloses, and pectin - which requires them to possess an adequate arsenal of plant cell wall degrading enzymes (PCWDEs) present in their digestive tract. Genomic data for Cerambycidae are mostly limited to notorious forest pests and are lacking for most major taxonomic groups. Consequently, our understanding of the distribution and evolution of cerambycid PCWDEs is quite limited. We documented the numbers, kinds, and evolution of cerambycid PCWDEs by surveying larval midgut transcriptomes from 23 species representing six of the eight recognized subfamilies of Cerambycidae. Using these data, we identified 340 new putative PCWDEs belonging to ten CAZyme families, making this by far the most comprehensive comparative genomic study of cerambycid PCWDEs to date. The wide range of PCWDEs expressed by Cerambycidae should allow them to break down most PCW polysaccharides. The phylogenetic distribution of PCWDEs we observed suggests that cerambycid food sources (e.g., healthy, weakened, or decayed/rotten wood) may not have played a major role in shaping the evolutionary history of these enzyme families encoded in cerambycid genomes.