Members of the tomato LeEIL (EIN3-like) gene family are functionally redundant and regulate ethylene responses throughout plant development

The plant hormone ethylene regulates many aspects of growth, development an d responses to the environment. The Arabidopsis ETHYLENE INSENSITIVE3 (EIN3 ) protein is a nuclear-localized component of the ethylene signal-transduct ion pathway with DNA-binding activity. Loss-of-function mutations in this p rotein result in ethylene insensitivity in Arabidopsis. To gain a better un derstanding of the ethylene signal-transduction pathway in tomato, we have identified three homologs of the Arabidopsis EIN3 gene (LeEILs). Each of th ese genes complemented the ein3-1 mutation in transgenic Arabidopsis, indic ating that all are involved in ethylene signal transduction. Transgenic tom ato plants with reduced expression of a single LeEIL gene did not exhibit s ignificant changes in ethylene response; reduced expression of multiple tom ato LeEIL genes was necessary to reduce ethylene sensitivity significantly. Reduced LeEIL expression affected all ethylene responses examined, includi ng leaf epinasty, flower abscission, flower senescence and fruit ripening. Our results indicate that the LeEILs are functionally redundant and positiv e regulators of multiple ethylene responses throughout plant development.