ARABIDOPSIS ETHYLENE-RESPONSE GENE ETR1 - SIMILARITY OF PRODUCT TO 2-COMPONENT REGULATORS

Ethylene behaves as a hormone in plants, regulating such aspects of gr owth and development as fruit ripening, flower senescence, and absciss ion. Ethylene insensitivity is conferred by dominant mutations in the ETR1 gene early in the ethylene signal transduction pathway of Arabido psis thaliana. The ETR1 gene was cloned by the method of chromosome wa lking. Each of the four known etr1 mutant alleles contains a missense mutation near the amino terminus of the predicted protein. Although th e sequence of the amino-terminal half of the deduced ETR1 protein appe ars to be novel, the carboxyl-terminal half is similar in sequence to both components of the prokaryotic family of signal transducers known as the two-component systems. Thus, an early step in ethylene signal t ransduction in plants may involve transfer of phosphate as in prokaryo tic two-component systems. The dominant etr1-1 mutant gene conferred e thylene insensitivity to wild-type Arabidopsis plants when introduced by transformation.