** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** CROP PLANTS RESPOND TO PATHOGEN CHALLENGE BY ACTIVATING THEIR IMMUNE SYSTEMS. PLANT PATHOGENS, IN TURN, HAVE DEVELOPED WAYS TO COUNTER THESE DEFENSES. PROTEINS CALLED EFFECTORS ARE ONE SUCH COUNTER-DEFENSE. THESE PROTEINS WORK BY SHUTTING DOWN, OR SUPPRESSING, IMMUNE RESPONSES IN PLANTS, EFFECTIVELY ENABLING THE PATHOGEN INVASION. WHEN WE LEARN ABOUT HOW EFFECTORS WORK, AND WHICH PLANT IMMUNITY COMPONENTS THEY TARGET, WE CAN USE THIS INFORMATION TO DEVELOP NEW SUSTAINABLE WAYS TO MANAGE DISEASE IN CROPS. THIS PROJECT WILL PRODUCE THIS KNOWLEDGE FOR A UNIQUE, AND ECONOMICALLY DAMAGING GROUP OF PLANT PATHOGENS CALLED LIBERIBACTERS. LIBERIBACTERS ARE TRANSMITTED BY INSECTS CALLED PSYLLIDS AND ARE CAUSAL AGENTS OF DISEASE IN CITRUS, TOMATO, POTATO, CARROTS, AND CELERY. THEY INVADE CELLS OF BOTH PLANT AND PSYLLID HOSTS. IN PLANT HOSTS, LIBERIBACTERS CAUSE MANY UNIQUE SYMPTOMS, WHICH WE HYPOTHESIZE ARE DUE TO THE ACTIVITY OF EFFECTORS. WE WILL CARRY OUT EXPERIMENTS TO UNDERSTAND HOW EFFECTORS CAUSE DISEASE, HOW DISEASE SYMPTOMS MAY ENCOURAGE ATTRACTION OF PSYLLID VECTORS, AND HOW EFFECTORS ARE ALTERING THE PLANT IMMUNE SYSTEM. ONCE WE KNOW HOW EFFECTORS ALTER PLANT IMMUNITY AND PLANT INTERACTIONS WITH PSYLLID VECTORS, WE CAN USE THIS INFORMATION TO IMPROVE LIBERIBACTER AND PSYLLID MANAGEMENT. EXAMPLES OF RELEVANT APPLICATIONS INCLUDE: IMPROVED CROP BREEDING TO CREATE VARIETIES WITH IMMUNE SYSTEM COMPONENTS THAT CANNOT BE MANIPULATED BY EFFECTORS, AND THERAPEUTICS (LOW-, OR NO-TOXICITY CHEMICAL TREATMENTS) THAT BIND AND DISABLE EFFECTORS DURING INFECTIONS IN PLANTS. OUR PROJECT WILL ALSO GENERATE KNOWLEDGE OF LIBERIBACTER GENETICS AND BIOLOGY THAT WILL HELP US UNDERSTAND HOW AND WHY THESE PATHOGENS EMERGE AS CAUSAL AGENTS OF DISEASE IN CROPS.