Fischer-Iglesias C, Sundberg B, Neuhaus G, Jones A M
University of Freiburg, Institute of Biology II, Cell Biology, Schänzlestrasse 1, D-79104 Freiburg, Germany.
Plant J. 2001 Apr;26(2):115-29. doi: 10.1046/j.1365-313x.2001.01013.x.
Inhibitors of auxin polar transport disrupt normal embryogenesis and thus specific spatial auxin distribution due to auxin movement may be important in establishing embryonic pattern formation in plants. In the present study, the distribution of the photoaffinity labeling agent tritiated 5-azidoindole-3-acetic acid ([3H],5-N3IAA), an analog of indole-3-acetic acid (IAA), was visualized in zygotic wheat (Triticum aestivum L.) embryos grown in vitro and in planta, and used to deduce auxin transport pathways in these embryos. This study provides the first direct evidence that the distribution of auxin, here [3H],5-N3IAA, is heterogeneous and changes during embryo development. In particular, the shift from radial to bilateral symmetry was correlated with a redistribution of [3H],5-N3IAA in the embryo. Furthermore, in bilaterally symmetrical embryos, that is, embryos in the late transition stage or older, the localization of [3H],5-N3IAA was altered by N-1-naphthylphthalamic acid, a specific inhibitor of auxin polar transport. No significant effect was observed in radially symmetrical embryos, that is, globular embryos, or very early transition embryos. Thus, the shift from radial to bilateral symmetry is associated with the onset of active, directed auxin transport involved in auxin redistribution. A change in the distribution of [3H],5-N3IAA was also observed in morphologically abnormal embryos induced on media supplemented with auxin or auxin polar transport inhibitors. By means of a microscale technique, free IAA concentration was measured in in vitro- and in planta-grown embryos and was found to increase during development. Therefore, IAA may be synthesized or released from conjugates in bilaterally symmetrical embryos, although import from surrounding tissues cannot be excluded.
生长素极性运输抑制剂会破坏正常的胚胎发育，因此由于生长素移动导致的特定空间生长素分布，对于植物胚胎模式形成的建立可能很重要。在本研究中，对吲哚 - 3 - 乙酸（IAA）的类似物、光亲和标记剂氚化5 - 叠氮吲哚 - 3 - 乙酸（[³H]，5 - N₃IAA）在体外和体内生长的小麦（Triticum aestivum L.）合子胚中的分布进行了可视化，并用于推断这些胚中的生长素运输途径。本研究提供了首个直接证据，即生长素（此处为[³H]，5 - N₃IAA）的分布是不均匀的，且在胚胎发育过程中会发生变化。特别是，从辐射对称到两侧对称的转变与胚中[³H]，5 - N₃IAA的重新分布相关。此外，在两侧对称的胚中，即处于晚期过渡阶段或更老的胚中，[³H]，5 - N₃IAA的定位会被生长素极性运输的特异性抑制剂N - 1 - 萘基邻苯二甲酰胺改变。在辐射对称的胚中，即球形胚或非常早期的过渡胚中，未观察到显著影响。因此，从辐射对称到两侧对称的转变与参与生长素重新分布的活跃、定向生长素运输的开始有关。在添加了生长素或生长素极性运输抑制剂的培养基上诱导产生的形态异常胚中，也观察到了[³H]，5 - N₃IAA分布的变化。通过一种微尺度技术，对体外和体内生长的胚中的游离IAA浓度进行了测量，发现其在发育过程中会增加。因此，IAA可能在两侧对称的胚中从结合物中合成或释放，尽管不能排除从周围组织的输入。
