Activation of the Ethylene Gas Response Pathway in Arabidopsis by the Nuclear Protein ETHYLENE-INSENSITIVE3 and Related Proteins

Mutations in the Arabidopsis ETHYLENE-INSENSITIVE3 (EIN3) gene severely limit a plant's response to the gaseous hormone ethylene. ein3 mutants show a loss of ethylene-mediated effects including gene expression, the triple response, cell growth inhibition, and accelerated senescence. EIN3 acts downstream of the histidine kinase ethylene receptor, ETR1, and the Raf-like kinase, CTR1. The EIN3 gene encodes a novel nuclear-localized protein that shares sequence similarity, structural features, and genetic function with three EIN3-LIKE (EIL) proteins. In addition to EIN3, EIL1 orEIL2 were able to complement ein3, suggesting their participation in the ethylene signaling pathway. Overexpression of EIN3 or EIL1 in wild-type or ethylene-insensitive2 plants conferred constitutive ethylene phenotypes, indicating their sufficiency for activation of the pathway in the absence of ethylene.