ABSTRACT Arabidopsis thaliana seedlings exhibit longer hypocotyls when they are grown under high ambient temperature, which is defined as thermomorphogenesis. Although it is well established that high temperature triggers auxin biosynthesis to stimulate hypocotyl elongation, the physiological functions of other endogenous phytohormones during thermomorphogenesis are still elusive. Here, we report that exogenous application of abscisic acid (ABA) strongly inhibits hypocotyl elongation under high ambient temperature. Hypocotyl elongations of ABA biosynthesis deficient mutants are more sensitive to high temperature, suggesting that endogenous ABA has a robust inhibition effect. Moreover, blocking ABA perception or signaling impedes the negative effect of ABA. Finally, we show that ABA also suppresses the hypersensitivity to high temperature of an auxin over-accumulation mutant (yuc1D), indicating that activation of auxin signaling is not sufficient to override the repression by ABA. Taken together, we demonstrate that ABA is a negative regulator during plant thermomorphogenesis.

中文翻译：

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脱落酸抑制拟南芥的热形态发生

摘要 拟南芥幼苗在高环境温度下生长时表现出更长的下胚轴，这被定义为热形态发生。尽管已经确定高温触发生长素生物合成以刺激下胚轴伸长，但其他内源性植物激素在热形态发生过程中的生理功能仍然难以捉摸。在这里，我们报告外源性应用脱落酸（ABA）在高环境温度下强烈抑制下胚轴伸长。ABA 生物合成缺陷突变体的下胚轴伸长对高温更敏感，表明内源性 ABA 具有强大的抑制作用。此外，阻断 ABA 感知或信号传导会阻碍 ABA 的负面影响。最后，我们表明 ABA 还抑制了生长素过度积累突变体 (yuc1D) 对高温的超敏反应，表明生长素信号传导的激活不足以克服 ABA 的抑制。综上所述，我们证明 ABA 在植物热形态发生过程中是一种负调节剂。