White C N, Proebsting W M, Hedden P, Rivin C J
Department of Botany and Plant Pathology, Center for Gene Research and Biotechnology, Oregon State University, Corvallis, OR 97331-2902, USA.
Plant Physiol. 2000 Apr;122(4):1081-8. doi: 10.1104/pp.122.4.1081.
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.
脱落酸（ABA）对于调控玉米（Zea mays L.）种子成熟是必需的。在ABA合成过程中受阻的突变体（如胎萌-5）不能成熟为静止的、耐干燥的种子，而是在籽粒发育中途就在穗上萌发。由于赤霉素（GA）和ABA在植物发育的许多方面起拮抗作用，我们推测ABA拮抗GA促进玉米早熟萌发的正向信号。在这些实验中，我们表明，在种子发育早期通过遗传诱导或生物合成抑制剂诱导的GA缺乏，可抑制ABA缺乏的发育中籽粒的胎萌。所产生的种子具有耐干燥性和贮藏寿命。对野生型籽粒中GA积累的时间分析表明，在ABA含量达到峰值之前，生物活性GA(1)和GA(3)就已积累。我们推测，这些GA在缺乏正常量ABA的情况下刺激导致胎萌的发育程序，而GA含量的降低重新建立了适合抑制萌发和诱导成熟的ABA/GA比值。相反，GA缺乏的诱导并没有抑制胎萌-1突变体籽粒的胎萌，这表明VP1在调控种子发育过程中作用于GA和ABA的下游。
