OsEIL1, a Rice Homolog of the Arabidopsis EIN3 Regulates the Ethylene Response as a Positive Component

The plant gaseous hormone ethylene regulates many aspects of plant growth, development and responses to the environment. ETHYLENE INSENSITIVE3 (EIN3) is a transcription factor involved in the ethylene signal transduction pathway in Arabidopsis. To gain a better understanding of the ethylene signal transduction pathway in rice, six EIN3-like genes (designated OsEIL1–6) were identified. OsEIL1, which showed highest similarity with EIN3, was isolated and functionally characterized. Ectopic expression of OsEIL1 in Arabidopsis can partially complement the ein3-1 mutant. The transgenic rice plants with overexpression of OsEIL1 exhibit short root, coiled primary root and slightly short shoot phenotype and elevated response to exogenous ethylene. OsEBP89, an ethylene responsive element binding protein (EREBP) and OsACO1, an ACC (1-aminocyclopropane-1-carboxylic acid) oxidase gene were enhanced in the OsEIL1 overexpressing transgenic plants. These results indicate that OsEIL1 is involved in ethylene signal transduction pathway and acts as a positive regulator of ethylene response in rice.