9728133 Klee The interactions of plants and disease-causing pathogens generally fall into two types: compatible and incompatible. Incompatibility leads to resistance while compatibility leads to disease. In the absence of a resistant response, disease symptoms can spread leading to severe damage or death of the plant. Using an ethylene-insensitive tomato mutant, we have demonstrated a central role for this phytohormone in disease symptom development in compatible tomato:pathogen interactions. We intend, through the use of mutants, to define how ethylene controls disease development in compatible plant:pathogen interactions. Experiments will define at a molecular genetic level the role of ethylene in symptom development in the tomato:Xanthomonas interaction. Using plants altered in ethylene synthesis or perception as well as plants deficient in accumulation of salicylic acid (SA), the PIs will characterize the roles of ethylene and SA in regulating early and advanced stages of disease. The PIs will also examine a compatible interaction in Arabidopsis. An understanding of how ethylene insensitivity attenuates symptom development to multiple pathogenic organisms also offers the possibility of broad and durable host tolerance with significant applications to agriculture.
