Plant Ecophysiology, Institute of Environmental Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
Planta. 2012 Apr;235(4):677-85. doi: 10.1007/s00425-011-1528-3. Epub 2011 Oct 19.
Upward leaf movement (hyponastic growth) is adopted by several plant species including Arabidopsis thaliana, as a mechanism to escape adverse growth conditions. Among the signals that trigger hyponastic growth are, the gaseous hormone ethylene, low light intensities, and supra-optimal temperatures (heat). Recent studies indicated that the defence-related phytohormones jasmonic acid (JA) and salicylic acid (SA) synthesized by the plant upon biotic infestation repress low light-induced hyponastic growth. The hyponastic growth response induced by high temperature (heat) treatment and upon application of the gaseous hormone ethylene is highly similar to the response induced by low light. To test if these environmental signals induce hyponastic growth via parallel pathways or converge downstream, we studied here the roles of Methyl-JA (MeJA) and SA on ethylene- and heat-induced hyponastic growth. For this, we used a time-lapse camera setup. Our study includes pharmacological application of MeJA and SA and biological infestation using the JA-inducing caterpillar Pieris rapae as well as mutants lacking JA or SA signalling components. The data demonstrate that MeJA is a positive, and SA, a negative regulator of ethylene-induced hyponastic growth and that both hormones repress the response to heat. Taking previous studies into account, we conclude that SA is the first among many tested components which is repressing hyponastic growth under all tested inductive environmental stimuli. However, since MeJA is a positive regulator of ethylene-induced hyponastic growth and is inhibiting low light- and heat-induced leaf movement, we conclude that defence hormones control hyponastic growth by affecting stimulus-specific signalling pathways.
向上的叶片运动（下胚轴生长）被包括拟南芥在内的几种植物物种采用，作为逃避不利生长条件的机制。触发下胚轴生长的信号包括气态激素乙烯、低光强度和超最佳温度（热）。最近的研究表明，植物在受到生物侵害时合成的与防御相关的植物激素茉莉酸（JA）和水杨酸（SA）抑制低光诱导的下胚轴生长。高温（热）处理和应用气态激素乙烯诱导的下胚轴生长反应与低光诱导的反应非常相似。为了测试这些环境信号是否通过平行途径或在下游汇聚诱导下胚轴生长，我们在这里研究了 Methyl-JA（MeJA）和 SA 在乙烯和热诱导的下胚轴生长中的作用。为此，我们使用了延时摄像机设置。我们的研究包括 MeJA 和 SA 的药理学应用以及使用诱导 JA 的鳞翅目毛毛虫 Pieris rapae 进行生物侵害以及缺乏 JA 或 SA 信号成分的突变体。数据表明，MeJA 是乙烯诱导的下胚轴生长的正调节剂，而 SA 是负调节剂，两种激素都抑制对热的反应。考虑到以前的研究，我们得出结论，SA 是在所有测试的诱导环境刺激下抑制下胚轴生长的众多测试成分中的第一个。然而，由于 MeJA 是乙烯诱导的下胚轴生长的正调节剂，并且抑制低光和热诱导的叶片运动，我们得出结论，防御激素通过影响刺激特异性信号通路来控制下胚轴生长。
