Adventitious roots (ARs) are an important root type for plants and display a high phenotypic plasticity in response to different environmental stimuli. Previous studies found that dark–light transition can trigger AR formation from the hypocotyl of etiolated Arabidopsis thaliana, which was used as a model for the identification of regulators of AR biogenesis. However, the central regulatory machinery for darkness‐induced hypocotyl AR (HAR) remains elusive. Here, we report that photoreceptors suppress HAR biogenesis through regulating the molecular module essential for lateral roots. We found that hypocotyls embedded in soil or in continuous darkness are able to develop HARs, wherein photoreceptors act as negative regulators. Distinct from wound‐induced ARs that require WOX11 and WOX12, darkness‐induced HARs are fully dependent on ARF7, ARF19, WOX5/7, and LBD16. Further studies established that PHYB interacts with IAA14, ARF7, and ARF9. The interactions stabilize IAA14 and inhibit the transcriptional activities of ARF7 and ARF19 and thus suppress biogenesis of darkness‐induced HARs. This finding not only revealed the central machinery controlling HAR biogenesis but also illustrated that AR formation could be initiated by multiple pathways.

中文翻译：

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光敏色素 B 通过稳定 IAA14 和抑制 ARF7 和 ARF19 抑制黑暗诱导的下胚轴不定根形成

不定根 (ARs) 是植物的重要根类型，对不同环境刺激表现出高度的表型可塑性。先前的研究发现，暗光转变可以触发黄化拟南芥下胚轴的 AR 形成，它被用作识别 AR 生物发生调节剂的模型。然而，黑暗诱导的下胚轴 AR（HAR）的中央调节机制仍然难以捉摸。在这里，我们报告光感受器通过调节侧根必不可少的分子模块来抑制 HAR 生物发生。我们发现嵌入土壤或连续黑暗中的下胚轴能够产生 HAR，其中光感受器充当负调节器。与需要 WOX11 和 WOX12 的伤口诱导的 AR 不同，黑暗诱导的 HAR 完全依赖于 ARF7、ARF19、WOX5/7 和 LBD16。进一步的研究确定 PHYB 与 IAA14、ARF7 和 ARF9 相互作用。这些相互作用稳定了 IAA14 并抑制了 ARF7 和 ARF19 的转录活性，从而抑制了黑暗诱导的 HAR 的生物发生。