The an1-4736 mutation of anther ear1 in maize alters scotomorphogenesis and the light response

Dwarf mutants have been instrumental in the elucidation of gibberellin (GA) metabolism and of their role on a wide range of plant physiological processes. Based on their response to the application of exogenous GAs, dwarf mutants have been divided into two major groups, GA-responsive and GA-insensitive mutants. Here we report on the characterization of an1-4736, a chemically (EMS) induced allele of an1 that belongs to the GA-responsive group. Striking aspects of this mutant allele are its early developmental time of response to GA3 administration and its capacity to partially repress scotomorphogenesis. When grown in continuous darkness the mutant shows traits usually associated with light-grown plants, such as leaf unfolding, reduction in seedling elongation and induction of light controlled genes. A partial impairment of mutant growth is also observed upon its transfer to light. Since other light-regulated processes appear normal in the mutant, it might be that the lesion in the GA metabolism specifically affects the light dependent signal pathway controlling plant elongation.These results, suggesting a dual role of GAs, one of promotion of stem elongation in light and a second one of repression of photomorphogenesis in darkness, are indicative of an interaction between GAs and light signals in the modulation of growth.