With the goal of understanding the basic biology of Oryctes rhinoceros, focusing on their potential symbioses as well as their digestive, detoxification, and antimicrobial genes, we ran the first next-generation sequencing study of the species. A nuclear and mitochondrial DNA population genetics analysis across its range from Thailand to Hawai’i found minimum variation, concurrent with rapid invasion but also suggesting that the genetic data from beetles in one part of the Pacific will be the same for as those from beetles across its range.
Molecular data on Oryctes rhinoceros is sorely lacking, with the closest being the draft genome of Oryctes borbonicus.
#Asiatic rhinoceros beetle plus
Any symbionts would also be targets for control, as knocking out an obligate symbiont with antimicrobials is an effective control of the host insect, plus symbionts themselves can be used to mediate RNAi delivery for bioncontrol. The possibility exists that Oryctes rhinoceros depends on symbiotic microbes for digestion, especially the production of PCWDEs. Disabling the larval ability to detoxify plant secondary compounds or chemical insecticides or their ability to digest food could prove fatal. These, plus any immune system, xenobiotic metabolism, or detoxification enzymes, would also be targets for next generation insecticides such as RNAi. These enzymes have great potential for biofuel production, and scarab digestive tracts have already been highlighted as potential sources of enzymes for bioreactors.
Īnother potential application of the beetles’ molecular biology is for plant cell wall degrading enzymes (PCWDEs) such as cellulases and hemicellulases. Studying these peptides not only helps us understand the beetle’s defenses against potential biocontrol pathogens, but also may have applications in medicine through the constant search for new antimicrobials. Part of the beetle’s immunity includes antimicrobial peptides (AMPs), such as defensin, scarabaecin, oryctin, and rhinocerin. Fungi ( Metarhizium anisopliae M.) can kill the pest under certain conditions, as can nematodes and the Oryctes baculovirus, however a virus-immune haplotype of the beetle has been described, reducing viral effectiveness overall. The pest is mainly controlled through mechanical removal of adults. 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. A number of antimicrobial peptides are expressed, particularly by the fat body but also by the midgut and hindgut. 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. The gut microbiota of Oryctes rhinoceros larvae is quite similar to that of the termite gut, as both species feed on decaying wood. 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. Little molecular data exists for this pest, impeding our ability to develop effective countermeasures and deal with the species’ growing resistance to viral biocontrols. The coconut rhinoceros beetle, Oryctes rhinoceros, is a major pest of palm crops in tropical Asia and the Pacific Islands.
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