Prospects for deploying microbes against tree-killing beetles (Coleoptera) in Anthropocene

Abstract

Forests form rich biodiversity hubs that act as large reservoirs of natural carbon. The spatial and temporal heterogeneity of these complex habitats of forest floors provides ecological services of immense socio-economic importance. However, these socio-economic ecological hotspots are incessantly exposed to multifarious abiotic, biotic, and anthropogenic disturbances, amongst which unpredictable forest pest (i.e., bark beetle) outbreak account for the loss of vegetation and microbiome of measurable quantum. The importance of the microbiome in forming an inseparable functional unit of every host and shaping its interaction with other partners has been well realized. Interestingly, forest pests, including bark beetles, are also reported to rely on their endosymbiotic microbial partners to manipulate tree defense machinery. In contrast, the microbiome forming the holobiont of trees also regulates the overall function and fitness of the host and significantly contributes to tackling these challenging situations. Nevertheless, how the holobiont of trees directly or indirectly influence beetle holobiont is still an enigma. The present review shall elaborate on the role of microbial tools in enhancing tree performance and fitness, which helps counter beetle damage. Besides, it shall also emphasize exploiting the role of microorganisms in acting as biocontrol agents in shielding the trees against beetle destruction. The application of endosymbiont-mediated RNA interference (RNAi) in working with two-tier specificity for controlling beetle devastations shall be discussed as new-age technological advances. All explanations are expected to put forth the potential of the microbial toolbox in offering better and more sustainable beetle management strategies in the future.

Comparative metagenomic study unveils bacterial communities and their putative involvement in ecological success of two pine-feedingIpsbeetle holobionts

“…Current data will facilitate further downstream studies (metatranscriptomics, metaproteomics, and culture-based bacterial functional characterization) to characterize the critical bacterial species aiding these Ips beetles thriving on defence-rich pine trees. Such essential bacterial partners can be used for microbiome-based sustainable pest management practices (91, 101, 102). Finally, such knowledge can serve as a primer to decipher the underlying microbial interactions at the tree-beetle interface and facilitate the integration of tree-beetle-microbiome interaction data into spatial models of forest ecosystem dynamics predictions.…”

“…Other core members such as Dyella, Pseudoxanthomonas, Sphingomonas, Saccharomonospora, Acidisoma have the enzymatic competency to help the beetle metabolize complex carbohydrates found in the conifer cell wall (21,69,(87)(88)(89)(90). Therefore, such microbes belonging to the core bacteriome can be further evaluated in beetlo for potential benefits and targeted for future microbesmediated sustainable beetle management practices (91).…”

RNAi-chitosan biopesticides for managing forest insect pests: an outlook

“…Our colleagues from the United States are deploying fungal-induced gene silencing (FIGS) technology to manage bark beetles, i.e., genetically modifying the bark beetle-associated yeast Ogataea pini, to generate specific dsRNA molecules that target Ips calligraphus (information based on personal communication). Our team has also successfully identified and isolated insectsymbiotic bacteria and fungi (Chakraborty et al, 2020a(Chakraborty et al, ,b, 2023b and may use them as a CSMR for tropical application to control the bark beetles and termites (Gupta et al, 2023). Recently, our group identified 69 core bacterial genera and 19 fungal genera among six bark beetles (Ips typographus, Ips duplicatus, Ips cembrae; Ips sexdentatus, Ips acuminatus, and Polygraphus poligraphus).…”

“…Moreover, within termite-infested wood, fungal communities affiliated with the Eurotiales, Sordariales, Hypocreales, Trichospornales, and Ophiostomatales orders were identified, notably, the fungal genera Apiotrichum, Fusarium, Hawksworthiomyces, Lasiodiplodia, Sporothrix, Trichosporon, and Trichoderma displayed substantial prevalence in the termite-infested wood. As described thoroughly in our recent review, some identified microbial associates of bark beetle or termites can be good candidates for Symbiont-mediated RNAi or SMR (Gupta et al, 2023). Nevertheless, SMR technology can be considered for its potential in forest conservation; additional refinements are necessary before applications.…”

Understanding bark beetle outbreaks: exploring the impact of changing temperature regimes, droughts, forest structure, and prospects for future forest pest management

“…Recently, Mogilicherla and Roy (2023b) comprehensively reviewed chitosan-dsRNA nanopesticides and their applications in managing bark beetles. The bacteria and fungi that live symbiotically with bark beetles have been successfully isolated and identified and can be considered putative candidates for symbiont-mediated RNAi (SMT) for tropical application to control bark beetles (Chakraborty et al 2020a(Chakraborty et al , 2020b(Chakraborty et al , 2023Gupta et al 2023;Mogilicherla and Roy 2023b). These studies may pave the way for developing and using RNAi-biopesticides as a secure, efficient, and innovative method to safeguard forest trees.…”