XVI International Botanical Congess

The gaseous hormone ethylene regulates a variety of developmental processes and environmental responses in higher plants. Plants perceiveand respond to ethylene through a family of ethylene receptors typified by Arabidopsis ETR1. Expression of the first 128 amino acids of ETR1 in yeast is sufficient and necessary to provide ethylene-binding sites. This ethylene-binding domain shares 25% amino acid similarity to the cyanobacterium Synechocystis protein slr1212. Using homologous recombination to knockout slr1212 led to the elimination of ethylene-binding activity by Synechocystis cells, however, no role for ethylene signaling has been observed in prokaryotic cells. In addition to continuing the molecular and biochemical characterization of the plant ethylene-binding domain, approaches to determine the function of the bacterial ethylene-binding domain are underway. A survey of a variety of prokaryotic and eukaryotic organisms indicated that the ethylene-binding activity was restricted to some members of the cyanobacteria, green algae, and all major groups of land plants.