9513463 Bleecker The gaseous hormone ethylene regulates a number of important developmental processes in higher plants. The initial biochemical events involved in ethylene perception are being investigated in the plant Arabidopsis thaliana. The ETR1 gene in the plant codes for a protein with sequence homology to sensory receptor proteins of bacteria. Mutations in the ETR1 gene confer dominant insensitivity to ethylene. The role of the protein coded by ETR1 as an ethylene receptor was confirmed by expressing the ETR1 gene in yeast and finding that the transformed yeast binds ethylene to the ETR1 protein. Using the yeast expression system, altered forms of the ETR1 protein will be expressed to investigate the mechanism of binding and signal transduction. Using in vitro mutagenesis, effects of specific changes in single amino acid residues of the protein will be followed by analysis of the ability of the altered protein to bind ethylene when expressed in transgenic yeast, and to transduce the ethylene signal transgenic plants. In conjunction with work funded by other sources on the purification of the ETR1 protein from yeast, the proposed research will be used to construct a molecular model for the mechanism of action of this plant hormone receptor. In addition the novel mutant forms of the ETR1 gene identified in this study will provide biotechnologists with the ability to genetically engineer alterations in ethylene sensitivity in economically important plant species. ***
