White C N, 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):1089-97. doi: 10.1104/pp.122.4.1089.
Abscisic acid (ABA) is required for seed maturation in maize (Zea mays L.) and other plants. Gibberellins (GAs) are also present in developing maize embryos, and mutual antagonism of GAs and ABA appears to govern the choice between precocious germination or quiescence and maturation. Exogenous ABA can also induce quiescence and maturation in immature maize embryos in culture. To examine the role of GAs versus ABA in regulating maize embryo maturation, the effects of modulating GA levels were compared with those of ABA in embryos cultured at successive stages of development. The effects of GA synthesis inhibition or exogenous GA application differed markedly in embryos at different stages of development, indicating changes in both endogenous GA levels and in the capacity for GA synthesis as embryogenesis and maturation progress. In immature embryos, the inhibition of GA synthesis mimicked the effects of exogenous ABA, as shown by the suppression of germination, the acquisition of anthocyanin pigments, and the accumulation of a variety of maturation-phase mRNAs. We suggest that GA antagonizes ABA signaling in developing maize embryos, and that the changing hormone balance provides temporal control over the maturation phase.
脱落酸（ABA）是玉米（Zea mays L.）和其他植物种子成熟所必需的。赤霉素（GAs）也存在于发育中的玉米胚中，赤霉素和脱落酸之间的相互拮抗作用似乎决定了早熟萌发或休眠与成熟之间的选择。外源ABA也可诱导培养的未成熟玉米胚进入休眠和成熟状态。为了研究赤霉素与脱落酸在调节玉米胚成熟中的作用，将调节赤霉素水平的效果与在发育连续阶段培养的胚中脱落酸的效果进行了比较。赤霉素合成抑制或外源赤霉素处理的效果在发育的不同阶段的胚中差异显著，表明随着胚胎发生和成熟的进行，内源赤霉素水平和赤霉素合成能力都发生了变化。在未成熟胚中，赤霉素合成的抑制模拟了外源ABA的效果，表现为萌发受到抑制、花青素色素的获得以及多种成熟阶段mRNA的积累。我们认为，赤霉素在发育中的玉米胚中拮抗ABA信号，并且激素平衡的变化为成熟阶段提供了时间控制。
