Role of Gut Bacteria in Tomato Leaf Miner <i>Tuta absoluta</i> Gaining Resistance to α-Tomatine by Converting It to Cholesterol

<i>Tuta absoluta</i> is a worldwide invasive pest that causes severe losses in tomato industry in China, while its resistance mechanism to tomato's protective alkaloid of α-tomatine remains unclear. This study explores the role of its gut microbiota, and results showed that the abundance of the gut symbiont <i>Enterococcus mundtii</i> was significantly higher in <i>T. absoluta</i> feeding on wild-type tomatoes than that in those feeding on α-tomatine-deficient GAME2 mutant tomatoes. Isolated <i>E. mundtii</i> strain E14 degraded 72.2 ± 1.3% of α-tomatine in vitro; reinoculating it into antibiotic-treated <i>T. absoluta</i> restored the degradation ability. Inoculating E14 into five other lepidopteran pests (except noncolonized <i>Plutella xylostella</i>) enhanced their α-tomatine tolerance. Multiomics and in vitro pure-culture experiments showed that α-tomatine degrades into cholesterol via deglycosylation, reduction, and hydrolysis. This study reveals α-tomatine's dual role (toxin/cholesterol precursor) and <i>E. mundtii</i> as a key adaptation mediator, advancing our understanding of insect-plant coevolution and invasive pest control.