Ethylene-Binding Sites Generated in Yeast Expressing the Arabidopsis ETR1 Gene

Mutations in the ETR1 gene of Arabidopsis thaliana confer insensitivity to ethylene, which indicates a role for the gene product in ethylene signal transduction. Saturable binding sites for 14Cethylene were detected in transgenic yeast expressing the ETR1 protein, whereas control yeast lacking ETR1 showed no detectable ethylene binding. Yeast expressing a mutant form of ETR1 (etr1-1) also showed no detectable ethylene binding, which provides an explanation for the ethylene-insensitive phenotype observed in plants carrying this mutation. Expression of truncated forms of ETR1 in yeast provided evidence that the amino-terminal hydrophobic domain of the protein is the site of ethylene binding. It was concluded from these results that ETR1 acts as an ethylene receptor in Arabidopsis.