title: Gibberellins and seed development in maize. I. Evidence that gibberellin/abscisic acid balance governs germination versus maturation pathways.
abstract: Abscisic acid (ABA) is required for the regulation of seed maturation in maize (Zea mays L.). Mutants blocked in ABA synthesis (such as viviparous-5) do not mature to quiescent, desiccation-tolerant seeds, but germinate on the ear midway through kernel development. Because gibberellins (GA) and ABA act antagonistically in many aspects of plant development, we hypothesized that ABA antagonizes a positive GA signal for precocious germination in maize. In these experiments, we show that a GA deficiency early in seed development, induced genetically or via biosynthesis inhibitors, suppresses vivipary in ABA-deficient developing kernels. The resulting seeds have both desiccation tolerance and storage longevity. Temporal analysis of GA accumulation in wild-type kernels revealed the accumulation of bioactive GA(1) and GA(3) prior to the peak in ABA content. We speculate that these GAs stimulate a developmental program leading to vivipary in the absence of normal amounts of ABA, and that a reduction of GA content re-establishes an ABA/GA ratio appropriate for suppression of germination and induction of maturation. In contrast, the induction of a GA deficiency did not suppress vivipary in viviparous-1 mutant kernels, suggesting that VP1 acts downstream of both GA and ABA in programming seed development.
authors.affiliation: Department of Botany and Plant Pathology, Center for Gene Research and Biotechnology, Oregon State University, Corvallis, OR 97331-2902, USA.
authors.forename: C N
authors.initials: CN
authors.lastname: White
authors.forename: W M
authors.initials: WM
authors.lastname: Proebsting
authors.forename: P
authors.initials: P
authors.lastname: Hedden
authors.forename: C J
authors.initials: CJ
authors.lastname: Rivin
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D018525:Germination; D005875:Gibberellins / Q000378:metabolism*; D012639:Seeds / Q000254:growth & development*; D003313:Zea mays / Q000196:embryology / Q000378:metabolism*
chemical_list: D005875:Gibberellins; D000040:Abscisic Acid