Plant-Insect Interactions Shape Plasticity of Asian Longhorned Beetle Gut Microbiota

The Asian longhorned beetle (ALB; Anoplophora glabripennis) is an invasive, wood-boring pest capable of thriving in the heartwood of 24 deciduous host tree species in the United States where it faces a number of nutritional challenges, particularly digestion of lignocellulose and hemicellulose and nitrogen acquisition. Unlike other wood-boring beetles, which rely on cultivated fungal symbionts for the production of lignocellulose degrading and nutrient acquiring enzymes, we demonstrated that the majority of the challenging reactions, including digestion of lignin, cellulose, and hemicellulose occur within the ALB gut.  While midgut transcriptome profiling revealed that ALB endogenously produces a number of glycoside hydrolases that facilitate digestion of major hardwood polysaccharides, cooperation with gut microbes is required to neutralize the majority of these nutritional challenges.  Shotgun metagenomic profiling of gut microbes revealed a taxonomically diverse community with the metabolic capacity to completely degrade cellulose and hemicellulose, disrupt major linkages in the lignin polymer, convert xylose sugars that dominate hardwood hemicellulose into compounds that can be utilized by ALB, fix atmospheric nitrogen, and recycle nitrogenous waste products.  Thus, the metabolic potential of the gut community is complementary to ALB’s endogenous metabolic capabilities and encodes a more extensive suite of enzymes, enabling ALB to complete development in a broad host range.  Currently, we are investigating the impacts of host tree resistance on the gut community in poplar using 16s/ITS amplicon sequencing to study impacts on gut community diversity and deep Illumina sequencing to study the impacts on expression of insect and microbial digestive genes.