Millenaar Frank F, Cox Marjolein C H, van Berkel Yvonne E M de Jong, Welschen Rob A M, Pierik Ronald, Voesenek Laurentius A J C, Peeters Anton J M
Plant Ecophysiology, Utrecht University, 3584 CA Utrecht, The Netherlands.
Plant Physiol. 2005 Mar;137(3):998-1008. doi: 10.1104/pp.104.053967. Epub 2005 Feb 22.
Plants can reorient their organs in response to changes in environmental conditions. In some species, ethylene can induce resource-directed growth by stimulating a more vertical orientation of the petioles (hyponasty) and enhanced elongation. In this study on Arabidopsis (Arabidopsis thaliana), we show significant natural variation in ethylene-induced petiole elongation and hyponastic growth. This hyponastic growth was rapidly induced and also reversible because the petioles returned to normal after ethylene withdrawal. To unravel the mechanisms behind the natural variation, two contrasting accessions in ethylene-induced hyponasty were studied in detail. Columbia-0 showed a strong hyponastic response to ethylene, whereas this response was almost absent in Landsberg erecta (Ler). To test whether Ler is capable of showing hyponastic growth at all, several signals were applied. From all the signals applied, only spectrally neutral shade (20 micromol m(-2) s(-1)) could induce a strong hyponastic response in Ler. Therefore, Ler has the capacity for hyponastic growth. Furthermore, the lack of ethylene-induced hyponastic growth in Ler is not the result of already-saturating ethylene production rates or insensitivity to ethylene, as an ethylene-responsive gene was up-regulated upon ethylene treatment in the petioles. Therefore, we conclude that Ler is missing an essential component between the primary ethylene signal transduction chain and a downstream part of the hyponastic growth signal transduction pathway.
植物能够根据环境条件的变化重新定向其器官。在一些物种中，乙烯可通过刺激叶柄更垂直的方向（下弯）和增强伸长来诱导资源导向型生长。在这项对拟南芥（Arabidopsis thaliana）的研究中，我们发现乙烯诱导的叶柄伸长和下弯生长存在显著的自然变异。这种下弯生长诱导迅速且可逆，因为乙烯去除后叶柄恢复正常。为了揭示自然变异背后的机制，我们详细研究了乙烯诱导下弯的两个对比品系。哥伦比亚-0对乙烯表现出强烈的下弯反应，而在直立型兰茨贝格（Ler）中这种反应几乎不存在。为了测试Ler是否完全能够表现出下弯生长，我们施加了几种信号。在所有施加的信号中，只有光谱中性遮荫（20微摩尔·米-2·秒-1）能在Ler中诱导出强烈的下弯反应。因此，Ler具有下弯生长的能力。此外，Ler中缺乏乙烯诱导的下弯生长并非乙烯产生速率已饱和或对乙烯不敏感的结果，因为乙烯处理后叶柄中的一个乙烯反应基因被上调。因此，我们得出结论，Ler在初级乙烯信号转导链和下弯生长信号转导途径的下游部分之间缺少一个关键成分。
