THE ETHYLENE SIGNAL-TRANSDUCTION PATHWAY IN ARABIDOPSIS

The gaseous hormone ethylene is an important regulator of plant growth and development. Using a simple response of etiolated seedlings to et hylene as a genetic screen, genes involved in ethylene signal transduc tion have been identified in Arabidopsis. Analysis of two of these gen es that have been cloned reveals that ethylene signalling involves a c ombination of a protein (ETR1) with similarity to bacterial histidine kinases and a protein (CTR1) with similarity to Raf-1, a protein kinas e involved in multiple signalling cascades in eukaryotic cells. Severa l lines of investigation provide compelling evidence that ETR1 encodes an ethylene receptor. For the first time there is a glimpse of the mo lecular circuitry underlying the signal transduction pathway for a pla nt hormone.