• Plant growth and development are coordinated by multiple environmental and endogenous signals. Brassinosteroid (BR) and ethylene (ET) have overlapping functions in a wide range of developmental processes. However, the relationship between the BR and ET signalling pathways has remained unclear.
• Here, we show that BR and ET interdependently promote apical hook development and cell elongation through a direct interaction between BR-activated BRASSINOZALE-RESISTANT1 (BZR1) and ET-activated ETHYLENE INSENSITIVE3 (EIN3).
• Genetic analysis showed that BR signalling is required for ET promotion of apical hook development in the dark and cell elongation under light, and ET quantitatively enhances BR-potentiated growth. BZR1 interacts with EIN3 to co-operatively increase the expression of HOOKLESS1 and PACLOBUTRAZOL RESISTANCE FACTORs (PREs). Furthermore, we found that BR promotion of hook development requires gibberellin (GA), and GA restores the hookless phenotype of BR-deficient materials by activating EIN3/EIL1.
• Our findings shed light on the molecular mechanism underlying the regulation of plant development by BR, ET and GA signals through the direct interaction of master transcriptional regulators.

中文翻译：

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BZR1 和 EIN3 之间的相互作用介导油菜素内酯和乙烯之间的信号串扰

• 植物的生长和发育由多种环境和内源信号协调。油菜素内酯 (BR) 和乙烯 (ET) 在广泛的发育过程中具有重叠功能。然而，BR 和 ET 信号通路之间的关系仍不清楚。
• 在这里，我们表明 BR 和 ET 通过 BR 激活的 BRASSINOZALE-RESISTANT1 (BZR1) 和 ET 激活的 ETHYLENE INSENSITIVE3 (EIN3) 之间的直接相互作用相互依赖地促进顶端钩子发育和细胞伸长。
• 遗传分析表明 BR 信号是 ET 在黑暗中促进顶端钩发育和在光照下细胞伸长所必需的，并且 ET 在数量上增强了 BR 增强的生长。BZR1与EIN3相互作用，共同增加HOOKLESS1和多效唑耐药因子( PREs ) 的表达。此外，我们发现 BR 促进钩子发育需要赤霉素 (GA)，而 GA 通过激活 EIN3/EIL1 来恢复 BR 缺陷材料的无钩子表型。
• 我们的研究结果揭示了通过主转录调节因子的直接相互作用，BR、ET 和 GA 信号调控植物发育的分子机制。