The promotive effect of auxin on shoot cell expansion provided the bioassay used to isolate this central plant hormone nearly a century ago. While the mechanisms underlying auxin perception and signaling to regulate transcription have largely been elucidated, how auxin controls cell expansion is only now attaining molecular-level definition. The good news is that the decades-old acid growth theory invoking plasma membrane H+-ATPase activation is still useful. The better news is that a mechanistic framework has emerged, wherein Small Auxin Up RNA (SAUR) proteins regulate protein phosphatases to control H+-ATPase activity. In this review, we focus on rapid auxin effects, their relationship to H+-ATPase activation and other transporters, and dependence on TIR1/AFB signaling. We also discuss how some observations, such as near-instantaneous effects on ion transport and root growth, do not fit into a single, comprehensive explanation of how auxin controls cell expansion, and where more research is warranted. Expected final online publication date for the Annual Review of Plant Biology, Volume 71 is April 29, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

中文翻译：

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快速生长素介导的细胞扩增

近一个世纪前，生长素对芽细胞扩张的促进作用提供了用于分离这种中央植物激素的生物测定。虽然生长素感知和信号调控转录的机制已经在很大程度上得到阐明，但生长素如何控制细胞扩增直到现在才获得分子水平的定义。好消息是，利用质膜 H+-ATPase 激活的几十年前的酸生长理论仍然有用。更好的消息是已经出现了一个机制框架，其中小生长素上调 RNA (SAUR) 蛋白调节蛋白磷酸酶以控制 H+-ATPase 活性。在这篇综述中，我们关注快速生长素效应、它们与 H+-ATPase 激活和其他转运蛋白的关系，以及对 TIR1/AFB 信号的依赖。我们还讨论了一些观察结果，例如对离子转运和根生长的近乎瞬时的影响，不适合对生长素如何控制细胞扩张以及需要更多研究的单一、全面的解释。《植物生物学年度评论》第 71 卷的预计最终在线出版日期为 2020 年 4 月 29 日。请参阅 http://www.annualreviews.org/page/journal/pubdates 了解修订后的估计值。