Instituto de Biología Molecular y Celular de Plantas, 46022 Valencia, Spain.
Plant Physiol. 2011 Aug;156(4):1819-25. doi: 10.1104/pp.111.173971. Epub 2011 May 4.
Plants orient their growth depending on directional stimuli such as light and gravity, in a process known as tropic response. Tropisms result from asymmetrical accumulation of auxin across the responding organ relative to the direction of the stimulus, which causes differential growth rates on both sides of the organ. Here, we show that gibberellins (GAs) attenuate the gravitropic reorientation of stimulated hypocotyls of dark-grown Arabidopsis (Arabidopsis thaliana) seedlings. We show that the modulation occurs through induction of the expression of the negative regulator of auxin signaling INDOLE-3-ACETIC ACID INDUCIBLE19/MASSUGU2. The biological significance of this regulatory mechanism involving GAs and auxin seems to be the maintenance of a high degree of flexibility in tropic responses. This notion is further supported by observations that GA-deficient seedlings showed a much lower variance in the response to gravity compared to wild-type seedlings and that the attenuation of gravitropism by GAs resulted in an increased phototropic response. This suggests that the interplay between auxin and GAs may be particularly important for plant orientation under competing tropic stimuli.
植物根据光和重力等定向刺激来调整生长方向，这个过程被称为向性反应。向性是由于刺激器官中生长素的不对称积累相对于刺激方向引起的，这导致器官两侧的生长速度不同。在这里，我们表明赤霉素（GA）减弱了黑暗生长的拟南芥（Arabidopsis thaliana）幼苗受刺激下胚轴的向重力性重新定向。我们表明，这种调节作用是通过诱导生长素信号负调节剂 INDOLE-3-ACETIC ACID INDUCIBLE19/MASSUGU2 的表达来实现的。这种涉及 GA 和生长素的调节机制的生物学意义似乎是维持向性反应的高度灵活性。这一概念得到了以下观察结果的进一步支持：与野生型幼苗相比，GA 缺陷型幼苗对重力的反应方差要低得多，而 GA 对向重力性的减弱导致光向性反应增加。这表明，生长素和赤霉素之间的相互作用对于在竞争的向性刺激下植物的定向可能特别重要。
