Genetic analysis of ethylene signal transduction in Arabidopsis thaliana: Five novel mutant loci integrated into a stress response pathway

The response of Arabzdqsis thaliana etiolated seedlings to the plant hormone ethylene is a conspicuous phenotype known as the triple response. We have identified genes that are required for ethylene perception and response by isolating mutants that fail to display a triple response in the presence of exogenous ethylene. Five new complementation groups have been identified. Four of these loci, desig-nated Sn4, Sn5, Sn6 and Sn7, are insensitive to ethylene. The fifth complementation group, eirl, is defined by a novel class of mutants that have agravitropic and ethylene-insensitive roots. Double-mutant phenotypes have allowed the positioning of these loci in a genetic pathway for ethylene signal transduc-tion. The ethylene-response pathway is defined by the following loci: ETRI, EIN4, CTRI, EIN2, EIN3