Beetles upgrade plant toxins Using high resolution mass spectrometry and nuclear magnetic resonance (NMR), the researchers mapped which defensive molecules spruce trees produce and what happens to them inside beetle bodies.\u00a0<\/p>\n The surprise was not just that beetles tolerate these chemicals. It was that they chemically modified them into even stronger antimicrobials.\u00a0<\/p>\n The insects cleave off the sugar groups, converting phenolic glycosides into their sugar-free \u201caglycone\u201d forms. <\/p>\n The aglycones pack more antimicrobial punch and help the beetles fight off pathogenic fungi<\/a> encountered in their galleries.\u00a0<\/p>\n \u201cWe did not expect the beetles to be able to convert the spruce\u2019s defenses into more toxic derivatives in such a targeted way,\u201d said study lead author Ruo Sun.<\/p>\n Fungi slip past beetle defenses <\/p>\n The story doesn\u2019t end with the beetles\u2019 clever chemistry. The team turned to Beauveria bassiana, a well-known entomopathogenic fungus used in biocontrol, which has a mixed track record against bark beetles in the field.\u00a0<\/p>\n \u201cAlthough this fungus has not been effective in controlling bark beetles in the past, we found strains that had naturally infected and killed them. We therefore wanted to investigate more closely how they were able to successfully infect the beetles,\u201d Sun explained.<\/p>\n The study revealed a two-step detoxification pathway that lets B. bassiana slip past the beetle\u2019s upgraded defenses.\u00a0<\/p>\n First, the fungus re-adds a sugar to the toxic aglycones (glycosylation). Then it caps that sugar with a methyl group (methylation). The result is a methylglycoside derivative that neutralizes toxicity.\u00a0<\/p>\n This is safe for the fungus, and, crucially, resistant to the beetle enzymes that would normally snip sugars<\/a> back off and restore the antimicrobial form.\u00a0<\/p>\n Exploiting the beetle\u2019s strategy<\/p>\n Even more striking, beetles that had gorged on phenolic-rich spruce tissue proved more susceptible once the fungus performed this methylglycosylation, suggesting the pathogen can exploit the beetle\u2019s own chemical strategy. Mutant fungi without this pathway struggled to infect bark beetles, confirming that detox is not a side note. It\u2019s central to the pathogen\u2019s success.\u00a0<\/p>\n The genetics, the enzyme biochemistry, and the infection outcomes all aligned: methylglycosylation is the key that unlocks the beetle\u2019s chemical armor.<\/p>\n An evolutionary arms race <\/p>\n What emerges is a classic three-way arms race. The spruce tree outfits its bark with phenolics to block fungi. <\/p>\n The beetle co-opts those phenolics, converting them into more potent antifungals to protect itself and its brood. The fungus evolves a detox pipeline to neutralize those very compounds, reclaiming the upper hand.\u00a0<\/p>\n \u201cWe have demonstrated that a bark beetle can co-opt a tree\u2019s defensive compounds to make defenses against its own enemies,\u201d said study co-author Jonathan Gershenzon.<\/p>\n \u201cHowever, since one of the enemies, the fungus Beauveria bassiana, has developed the ability to detoxify these antimicrobial defenses, it can successfully infect the bark beetles and thus actually help the tree in its battle against bark beetles.\u201d<\/p>\n Ecologically, that twist matters. If fungal pathogens can reliably infect beetles even when those beetles weaponize spruce chemistry, the tree gains an indirect ally.\u00a0<\/p>\n In outbreak years \u2013 when Ips typographus can devastate spruce stands \u2013 knowing which fungal strains can slip past beetle defenses could tip management outcomes in the forest\u2019s favor.<\/p>\n The practical implications are direct. \u201cNow that we know which strains of the fungus tolerate the bark beetle\u2019s antimicrobial phenolic compounds, we can use these strains to combat bark beetles more efficiently,\u201d Sun said.\u00a0<\/p>\n Biocontrol programs can screen B. bassiana collections for robust methylglycosylation capacity and deploy those strains where spruce phenolics run high.\u00a0<\/p>\n Just as importantly, the study is a reminder to anticipate counter-adaptations: if a target pest<\/a> can repurpose host chemistry, any biological pesticide should be vetted for resistance-busting traits before field release.<\/p>\n Probing the detox machinery<\/p>\n The team\u2019s next steps focus on scope and synergy. They plan to survey how widespread the methylglycosylation pathway is across diverse B. bassiana strains and other beetle-killing fungi.\u00a0<\/p>\n In addition, they\u2019ll\u00a0 probe how this detox machinery interacts with additional pathogen traits \u2013 spore adhesion, cuticle penetration, growth rate \u2013 that shape infection success.\u00a0<\/p>\n Mapping that landscape could yield a recipe for high efficacy biocontrol consortia tailored to spruce stands under attack.<\/p>\n This work highlights a broader principle in chemical ecology: defensive molecules are not static shields. They flow through food webs, get metabolized, intensified, and disarmed, and in the process, they steer evolution on all sides \u2013 host, herbivore<\/a>, and pathogen.\u00a0<\/p>\n Here, spruce phenolics spark a cascade of conversions \u2013 from glycosides to aglycones to methylglycosides \u2013 that decides who wins at the bark-beetle\u2013fungus interface.\u00a0<\/p>\n Understanding those exchanges opens the door to smarter, more reliable ways to help forests withstand one of their most relentless adversaries.<\/p>\n The study is published in the journal Proceedings of the National Academy of Sciences<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com<\/a>.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"Spruce bark is packed with phenolic compounds that defend the tree against invading fungi. Those chemicals live in…\n","protected":false},"author":2,"featured_media":261688,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77],"tags":[18,19,17,7262,133],"class_list":{"0":"post-261687","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-eire","9":"tag-ie","10":"tag-ireland","11":"tag-plants","12":"tag-science"},"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@ie\/115820094214018943","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/261687","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/comments?post=261687"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/261687\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/261688"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=261687"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=261687"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=261687"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
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To test causality, the team knocked out the genes in B. bassiana that drive methylglycosylation. <\/p>\n