ROOT HAIRS ARE SINGLE-CELL EXTENSIONS THAT DIFFERENTIATE FROM THE ROOT EPIDERMIS AND CONTRIBUTE TO WATER AND NUTRIENT UPTAKE. ROOT HAIR DEVELOPMENT IS REGULATED IN RESPONSE TO CHANGING ENVIRONMENTAL CONDITIONS AND THESE STRUCTURES AREKEY TO PLANT SURVIVAL IN CONDITIONS OF LOW WATER OR NUTRIENT AVAILABILITY. IN THE MODEL PLANT ORGANISM, ARABIDOPSIS THALIANA, ROOT HAIRS ARE INDUCED BY THE GASEOUS HORMONE ETHYLENE AND ITS PRECURSOR, 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID (ACC). MY PRELIMINARY DATA INDICATES THAT ETHYLENE SIGNALING INDUCES REACTIVE OXYGEN SPECIES (ROS) ACCUMULATION IN ROOT HAIR CELLS PRIOR TO ROOT HAIR FORMATION. ROS ARE SMALL CHEMICALLY REACTIVE MOLECULES THAT ACT DOWNSTREAM OF MANY SIGNALING PATHWAYS TO DRIVE DEVELOPMENTAL PROCESSES. SIGNALING-INDUCED ROS ACT TO REVERSIBLY OXIDIZE CYSTEINE RESIDUES OF PROTEINS TO CHANGE THEIR FUNCTION AND/OR STABILITY.THIS PROJECT WILL BUILD ON PRELIMINARY ARABIDOPSIS DATA AND WILL EXAMINE WILD-TYPE AND ETHYLENE-INSENSITIVE TOMATO MUTANTS, NEVER-RIPE AND GREEN RIPE, GROWN IN THE PRESENCE OF ELEVATED ETHYLENE TO DETERMINE IF ETHYLENE DRIVES ROOT HAIR DEVELOPMENT THROUGH ROS ACCUMULATION. THIS PROJECT WILL ALSO DETERMINE TRANSCRIPTIONAL CONTROLS OF ETHYLENE-MEDIATED ROOT DEVELOPMENT AND WILL IDENTIFY PROTEINS THAT UNDERGO REVERSIBLE OXIDATION IN RESPONSE TO ETHYLENE SIGNALING.