GLUCOSE AND ETHYLENE SIGNAL-TRANSDUCTION CROSSTALK REVEALED BY AN ARABIDOPSIS GLUCOSE-INSENSITIVE MUTANT

Glucose is an essential signaling molecule that controls plant develop ment and gene expression through largely unknown mechanisms. To initia te the dissection of the glucose signal transduction pathway in plants by using a genetic approach, we have identified an Arabidopsis mutant , gin1 (glucose-insensitive), in which glucose repression of cotyledon greening and expansion, shoot development, floral transition, and gen e expression is impaired. Genetic analysis indicates that GINI acts do wnstream of the sensor hexokinase in the glucose signaling pathway. Su rprisingly, gin1 insensitivity to glucose repression of cotyledon and shoot development is phenocopied by ethylene precursor treatment of wi ld-type plants or by constitutive ethylene biosynthesis and constituti ve ethylene signaling mutants. In contrast, the ethylene insensitive m utant etr1-1 exhibits glucose hypersensitivity. Epistasis analysis pla ces GIN1 downstream of the ethylene receptor, ETR1, and defines a new branch of ethylene signaling pathway that is uncoupled from the triple response induced by ethylene. The isolation and characterization of g in1 reveal an unexpected convergence between the glucose and the ethyl ene signal transduction pathways. GINI may function to balance the con trol of plant development in response to metabolic and hormonal stimul i that act antagonistically.