Gibberellin dose-response curves and the characterization of dwarf mutants of barley
1999
Chandler, P.M. | Robertson, M.
Dose-response curves relating gibberellin (GA) concentration to the maximal leaf-elongation rate (LER(max)) defined three classes of recessive dwarf mutants in the barley (Hordeum vulgare L.) 'Himalaya.' The first class responded to low (10(-8)-10(-6) M) [GA(3)] (as did the wildtype). These grd (GA-responsive dwarf) mutants are likely to be GA-biosynthesis mutants. The second class of mutants, gse (GA sensitivity), differed principally in GA sensitivity, requiring approximately 100-fold higher [GA(3)] for both leaf elongation and alpha-amylase production by aleurone. This novel class may have impaired recognition between the components that are involved in GA signaling. The third class of mutant showed no effect of GA(3) on the LER(max). When further dwarfed by treatment with a GA-biosynthesis inhibitor, mutants in this class did respond to GA(3), although the LER(max) never exceeded that of the untreated dwarf. These mutants, called elo (elongation), appeared to be defective in the specific processes that are required for elongation rather than in GA signaling. When sln1 (slender1) wad introduced into these different genetic backgrounds, sln was epistatic to grd and gse but hypostatic to elo. Because the rapid leaf elongation typical of sln was observed in the grd and gse background, we inferred that rapid leaf elongation is the default state and suggest that GA action is mediated through the activity of the product of the Sln gene.
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