**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** GENETIC MODIFICATION (GM) OF INSECTS SUBJECT TO STERILE INSECT TECHNIQUE (SIT) HAVE RESULTED IN IMPROVEDMALE STERILIZATION BY CONDITIONAL LETHAL SYSTEMS THAT PREVENT THE PROGENY OF RELEASED MALES FROM SURVIVINGIN THE FIELD. THESE INCLUDE A TETRACYCLINE-SUPPRESSIBLE EMBRYONIC LETHALITY SYSTEM (TELS) THAT REQUIRES THEANTIBIOTIC FOR SURVIVAL, AND A DOMINANT TEMPERATURE SENSITIVE (DTS) MUTATION THAT RESULTS IN PUPAL LETHALITYAT TEMPERATURES ABOVE 29°C. BOTH SYSTEMS HAVE BEEN TRANSFORMED INTO THE GENOME OF THE CARIBBEAN FRUITFLY, ANASTREPHA SUSPENSA, RESULTING IN 100% LETHALITY UNDER RESTRICTIVE CONDITIONS. DESPITE THEIR EFFICIENCY,GENETIC APPROACHES TO PEST POPULATION CONTROL ARE SUBJECT TO GENETIC BREAKDOWN AND POSSIBLE RESISTANCEDUE TO SPONTANEOUS MUTATIONS OR MODIFIERS. THIS WAS DEMONSTRATED IN A DROSOPHILA TELS POPULATION INWHICH SPONTANEOUS TRANSGENE MUTATIONS AND SECOND-SITE MODIFIER/SUPPRESSORS RESULTED IN HERITABLESURVIVAL. A GOAL OF THIS PROPOSAL IS TO ASSESS THE GENETIC BREAKDOWN OF THE TELS SYSTEM IN A. SUSPENSAAND CERATITIS CAPITATA (MEDITERRANEAN FRUIT FLY) AND A ASDTS7 LETHALITY SYSTEM A. SUSPENSA. MASS-REAREDSTRAINS WILL BE TESTED INDIVIDUALLY TO DETERMINE THE FREQUENCY OF REVERTANT LETHAL MUTATIONS AND THEIRSTRUCTURE IN EACH SPECIES, AND IN COMBINATION IN A. SUSPENSA TO DETERMINE IF A DUAL-LETHALITY SYSTEM CANMITIGATE SURVIVAL FROM EITHER SYSTEM. FOR STRAINS TRANSFORMED WITH A TRANSPOSON VECTOR, ANOTHER SOURCE OFINSTABILITY IS POTENTIAL VECTOR RE-MOBILIZATION SINCE TRANSPOSONS ARE HORIZONTALLY TRANSMITTED (HT) IN NATURE.WHILE THE ORGANISMS THAT MEDIATE TRANSPOSON HT ARE UNKNOWN, WE HYPOTHESIZE THE INVOLVEMENT OFSYMBIOTIC BACTERIA, AND A SECOND GOAL WILL BE AN ASSESSMENT OF TRANSPOSON VECTOR HT FROM AN A.SUSPENSA HOST GENOME INTO ITS SYMBIOTIC BACTERIAL POPULATION. BY ASSESSING AND POSSIBLY MITIGATING GMINSECT INSTABILITY BY GENETIC BREAKDOWN AND TRANSPOSON VECTOR HORIZONTAL TRANSFER, THIS PROPOSAL ADDRESSESA HIGH PRIORITY FOR PROGRAM AREA 1. MANAGEMENT PRACTICES TO MINIMIZE ENVIRONMENTAL RISK OF GEORGANISMS.

Agricultural Research Service

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