Transcriptome and microbiome of coconut rhinoceros beetle (Oryctes rhinoceros) larvae

BACKGROUND: The coconut rhinoceros beetle, Oryctes rhinoceros, is a major pest of palm crops in tropical Asia and the Pacific Islands. Little molecular data exists for this pest, impeding our ability to develop effective countermeasures and deal with the species’ growing resistance to viral biocontrols. We present the first molecular biology analyses of this species, including a metagenomic assay to understand the microbiome of different sections of its digestive tract, and a transcriptomics assay to complement the microbiome data and to shed light on genes of interest like plant cell wall degrading enzymes and immunity and xenobiotic resistance genes. RESULTS: The gut microbiota of Oryctes rhinoceros larvae is quite similar to that of the termite gut, as both species feed on decaying wood. We found the first evidence for endogenous beta-1,4-endoglucanase in the beetle, plus evidence for microbial cellobiase, suggesting the beetle can degrade cellulose together with its gut microfauna. A number of antimicrobial peptides are expressed, particularly by the fat body but also by the midgut and hindgut. CONCLUSIONS: This transcriptome provides a wealth of data about the species’ defense against chemical and biological threats, has uncovered several potentially new species of microbial symbionts, and significantly expands our knowledge about this pest.