Rober-Kleber Nicole, Albrechtová Jolana T P, Fleig Sonja, Huck Norbert, Michalke Wolfgang, Wagner Edgar, Speth Volker, Neuhaus Gunther, Fischer-Iglesias Christiane
Institute for Biology II, Department of Cell Biology, Albert-Ludwigs-University of Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany.
Plant Physiol. 2003 Mar;131(3):1302-12. doi: 10.1104/pp.013466.
Previous investigations suggested that specific auxin spatial distribution due to auxin movements to particular embryonic regions was important for normal embryonic pattern formation. To gain information on the molecular mechanism(s) by which auxin acts to direct pattern formation in specific embryonic regions, the role of a plasma membrane (PM) ATPase was evaluated as downstream target of auxin in the present study. Western-blot analysis revealed that the PM H(+)-ATPase expression level was significantly increased by auxin in wheat (Triticum aestivum) embryos (two-three times increase). In bilaterally symmetrical embryos, the spatial expression pattern of the PM H(+)-ATPase correlates with the distribution pattern of the auxin analog, tritiated 5-azidoindole-3-acetic acid. A strong immunosignal was observed in the abaxial epidermis of the scutellum and in the epidermal cells at the distal tip of this organ. Pseudoratiometric analysis using a fluorescent pH indicator showed that the pH in the apoplast of the cells expressing the PM H(+)-ATPase was in average more acidic than the apoplastic pH of nonexpressing cells. Cellulose staining of living embryos revealed that cells of the scutellum abaxial epidermis expressing the ATPase were longer than the scutellum adaxial epidermal cells, where the protein was not expressed. Our data indicate that auxin activates the proton pump resulting in apoplastic acidification, a process contributing to cell wall loosening and elongation of the scutellum. Therefore, we suggest that the PM H(+)-ATPase is a component of the auxin-signaling cascade that may direct pattern formation in embryos.
先前的研究表明，生长素向特定胚胎区域移动所导致的特定生长素空间分布对于正常胚胎模式形成至关重要。为了获取有关生长素在特定胚胎区域指导模式形成的分子机制的信息，本研究评估了质膜（PM）ATP酶作为生长素下游靶点的作用。蛋白质免疫印迹分析显示，在小麦（Triticum aestivum）胚胎中，生长素显著提高了质膜H(+) - ATP酶的表达水平（增加了两到三倍）。在两侧对称的胚胎中，质膜H(+) - ATP酶的空间表达模式与生长素类似物——氚标记的5 - 叠氮吲哚 - 3 - 乙酸的分布模式相关。在盾片的远轴表皮以及该器官顶端的表皮细胞中观察到强烈的免疫信号。使用荧光pH指示剂进行的伪比率分析表明，表达质膜H(+) - ATP酶的细胞的质外体pH平均比未表达的细胞的质外体pH更酸。对活胚胎进行的纤维素染色显示，表达ATP酶的盾片远轴表皮细胞比未表达该蛋白的盾片近轴表皮细胞更长。我们的数据表明，生长素激活质子泵导致质外体酸化，这一过程有助于细胞壁松弛和盾片伸长。因此，我们认为质膜H(+) - ATP酶是生长素信号级联反应的一个组成部分，可能指导胚胎中的模式形成。
