CROPS ARE CONTINUALLY EXPOSED TO MICROBIAL PATHOGENS, WHICH CAUSE PLANT DISEASES, LEADING TO SEVERE YIELD LOSS. A MAJOR ROUTEOF PATHOGEN ENTRY INTO PLANTS IS THROUGH MICROSCOPIC PORES (STOMATA) FORMED BY PAIRS OF GUARD CELLS ON LEAF SURFACES. THE GOAL OFTHIS RESEARCH IS TO UNDERSTAND HOW METABOLITES PLAY REGULATORY ROLES IN PATHOGEN-TRIGGERED STOMATAL MOVEMENTS IN THE CONTEXT OFOTHER ENVIRONMENTAL CONDITIONS, SUCH AS DROUGHT AND RISING CARBON DIOXIDE IN THE ATMOSPHERE. THE FOLLOWING OBJECTIVES AREDESIGNED TO LINK ARABIDOPSIS OR TOMATO STOMATAL MOVEMENTS TO ENVIRONMENTAL CONDITIONS AND DISEASES: A) QUANTIFY METABOLITECHANGES DURING PATHOGEN-TRIGGERED STOMATAL CLOSING AND RE-OPENING. B) VERIFY ROLES OF GUARD CELL METABOLITES IN STOMATALAPERTURE REGULATION AND CHARACTERIZE INTERACTIONS IN DIFFERENT ENVIRONMENTAL CONDITIONS. C) ELUCIDATE GUARD CELL NETWORKS OFPATHOGEN-INDUCED STOMATAL CLOSURE AND RE-OPENING.