**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THE TWO-SPOTTED SPIDER MITE, TETRANYCHUS URTICAE (TSSM) IS AN EXTREME POLYPHAGOUS AGRICULTURAL PEST THAT FEEDS ON OVER 1100 PLANT SPECIES INCLUDING MORE THAN 150 CROPS WORLDWIDE. THIS SPECIES IS A RECORD-BREAKER IN DEVELOPMENT OF PESTICIDE RESISTANCE AMONG ARTHROPOD PESTS. IN COMBINATION WITH ITS INCREASED OUTBREAKS, ADAPTATION TO NOVEL HOST PLANTS AND CROP DAMAGE UNDER CONDITIONS OF CLIMATE CHANGE TSSM BECOMES ONE OF WORLD-WIDE HIGH-RISK PEST THAT THREATENS GLOBAL CROP SECURITY. THE EXISTENCE OF UNPRECEDENTED QUALITY OF GENOMIC RESOURCES AND GENETIC TOOLS AVAILABLE IN THIS SPECIES COUPLED WITH STRONG INTERNATIONAL RESEARCH COMMUNITY MAKES IT AN EXCELLENT PEST MODEL FOR DEVELOPMENT OF INNOVATIVE GENOMIC-BASED TECHNOLOGIES FOR PEST CONTROL. THE OVERALL AIM OF THE PROPOSAL IS TO DISSECT FUNCTION OF DETOXIFICATION ENZYMES IN ABILITY OF TSSM'S RAPID ADAPTATION TO DIFFERENT HOST PLANTS. OUR AIM IS TO UNDERSTAND THE ROLE OF TSSM'S OXYGENASES INVOLVED IN THE INTERPLAY BETWEEN HOST PLANTS DEFENSE (E.G. TOMATO AND ARABIDOPSIS) AND TSSM'S ABILITY TO OVERCOME DEFENSE RESPONSE AND ADOPT TO NEW HOST. IN THIS THIS PROPOSAL WE HAVE SELECTED TWO GROUPS OF ENZYMES: THOSE SPECIFICALLY ASSOCIATED WITH HOST SHIFT, AND ONES WHICH ARE OVEREXPRESSED AFTER ADAPTATION. MOLECULAR CHARACTERIZATION OF THE SELECTED PROTEINS WILL SPECIFICALLY FOCUS ON THE IDENTIFICATION OF THEIR NATURAL SUBSTRATES THAT ARE CURRENTLY UNKNOWN. MOREOVER, THEIR BIOLOGICAL ROLES WILL BE DETERMINED USING A MULTIDISCIPLINARY APPROACH INVOLVING BOTH IN VITRO AND IN VIVO MODELS. THEIR BIOCHEMICAL CHARACTERIZATION IN COMBINATION WITH THEIR TISSUE LOCALIZATION AND RNAI-BASED GENE SILENCING WILL DETERMINE THEIR ROLE IN HERBIVORE-PLANT PEST ADAPTATION. TOGETHER, THIS WILL PROVIDE NEW KNOWLEDGE ON TSSM DETOXIFICATION MECHANISMS AT A BIOCHEMICAL AND ORGANISMAL LEVEL AND GENERATE TOOLS AND KNOWLEDGE FOR DEVELOPMENT NEW PEST CONTROL APPROACHES BASED ON BIOCHEMISTRY AND GENOMICS.