GREEN PEACH APHIDS (MYZUS PERSICAE) ARE WIDELY PREVALENT AGRICULTURAL PESTS THAT REDUCE YIELD BY CONSUMING PLANT NUTRIENTS AND TRANSMITTING VIRUSES TO NUMEROUS FRUITS, VEGETABLES, AND FIELD CROPS. APHIDS FEED PRIMARILY FROM THE PHLOEM SIEVE ELEMENTS OF THEIR HOST PLANTS. IN THE COURSE OF PHLOEM FEEDING, APHIDS ALTERNATE BETWEEN SECRETING PROTEIN-CONTAINING SALIVA INTO SIEVE ELEMENTS AND INGESTING PHLOEM SAP. SEVERAL STUDIES HAVE DEMONSTRATED THAT SPECIFIC APHID SALIVARY PROTEINS, ALSO CALLED EFFECTORS, PLAY A CRITICAL ROLE IN SUCCESSFUL APHID FEEDING. CONVERSELY, SOME SALIVARY PROTEINS ELICIT VISIBLE RESPONSES IN PLANT LEAVES, SUGGESTING THAT PLANTS RECOGNIZE THESE INDIVIDUAL APHID PROTEINS AND INITIATE DEFENSES. HOWEVER, ONLY A FEW OF THE LIKELY DOZENS OF PROTEINS IN APHID SALIVA HAVE BEEN CHARACTERIZED, AND THE FUNCTIONS OF MOST APHID SALIVARY PROTEINS REMAIN COMPLETELY UNKNOWN. THE WIDE HOST RANGE OF GREEN PEACH APHIDS SUGGESTS THAT THIS SPECIES HAS A PARTICULARLY EFFECTIVE COMPLEMENT OF SALIVARY PROTEINS THAT FUNCTION BOTH IN SUPPRESSING PLANT DEFENSES AND IN PROMOTING NUTRIENT FLOW TO APHID FEEDING SITES.IN THE COURSE OF THIS PROJECT, THE FUNCTIONS OF SIX GREEN PEACH APHID SALIVARY PROTEINS WILL BE CHARACTERIZED. TWO OF THESE PROTEINS APPEAR TO ELICIT PLANT DEFENSE RESPONSES. FOUR OTHERS MOVE TO SPECIFIC LOCATIONS WITHIN THE PLANT CELLS FROM WHICH THE APHIDS ARE FEEDING, SUGGESTING THAT THEY HAVE A ROLE IN MANIPULATING PLANT METABOLISM FOR THE BENEFIT OF THE APHIDS. THE EFFECTS OF APHID SALIVARY PROTEINS WILL BE CHARACTERIZED WITH PLANT GENE EXPRESSION AND METABOLITE PROFILING ASSAYS. PROTEIN INTERACTION STUDIES WILL IDENTIFY PLANT PROTEINS THAT CONTRIBUTE TO THE RECOGNITION OF APHID FEEDING, AS WELL AS PLANT PROTEINS THAT ARE TARGETED BY THE APHIDS TO SUPPRESS PLANT DEFENSES AND PROMOTE NUTRIENT FLOW TO THE SITE OF APHID FEEDING. APHID GENE EXPRESSION SILENCING WILL DETERMINE THE EXTENT TO WHICH INDIVIDUAL SALIVARY PROTEINS ARE REQUIRED FOR SUCCESSFUL HOST PLANT UTILIZATION. CHARACTERIZATION OF ESSENTIAL APHID SALIVARY PROTEINS, AS WELL AS INTERACTIONS WITH ENDOGENOUS PLANT PROTEINS, WILL NOT ONLY PROVIDE A BETTER UNDERSTANDING OF FACTORS THAT CONTRIBUTE TO THE INVASIVENESS OF GREEN PEACH APHIDS, BUT ALSO WILL ENABLE THE IMPLEMENTATION OF NEW RESISTANCE MECHANISMS IN CROP PLANTS THROUGH BREEDING OR BIOTECHNOLOGY APPROACHES.