Enhanced chromium detoxification mediated by an arbuscular mycorrhizal fungus via arbutin‐derived hydroquinone

Summary Chromium (Cr) is a highly toxic carcinogen, posing serious ecological and health risks. Arbuscular mycorrhizal (AM) fungi, symbiotic partners of most terrestrial plants, transform highly toxic Cr(VI) into far less toxic Cr(III). However, how AM fungi mediate electron transfer and reduce Cr(VI) remains elusive. We employed metabolomics, functional group analysis, and electrochemical techniques searching for redox‐active substances that reduce Cr(VI). Further, in vivo and in vitro tests were conducted to decipher the Cr(VI) reduction mechanism. The AM fungus increased lettuce yield by 24% and lowered soil Cr (initial total Cr = 120 mg kg −1 ) bioavailability by 11%. Cr(VI) increased arbutin in the presence of the AM fungus. Through enzymatic reactions catalyzed by glucosidase, arbutin was subsequently decomposed to glucose and hydroquinone (H 2 Q). Glucose can support energy metabolic activities, while H 2 Q directly provides electrons to Cr(VI), thereby producing Cr(III). Additionally, H 2 Q can mitigate oxidative stress by reacting with hydroxyl radicals and can mobilize iron as a potential nutrient. We first discovered a previously ignored electron transfer mechanism facilitated by AM fungi in reducing Cr(VI) to Cr(III) for detoxification. Harnessing this fungal potential in real‐world conditions can efficiently detoxify Cr in the food chain, simultaneously reducing health risks and enhancing crop yield.