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 [ 14 C]ethylene 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 .