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