Complex antagonistic interactions between abscisic acid (ABA) and brassinosteroid (BR) signalling pathways have been widely documented. However, whether or how ABA interacts synergistically with BR in plants remains to be elucidated. Here, we report that low, but not high, concentration of ABA increases lamina joint inclination of rice seedling, which requires functional BR biosynthesis and signalling. Transcriptome analyses confirm that about 60% of low-concentration ABA early response genes can be regulated by BR in the same directions. ABA activates BR signal in a fast, limited and short-term manner and the BR-biosynthesis regulatory gene, OsGSR1, plays a key role during this process, whose expression is induced slightly by ABA through transcriptional factor ABI3. Moreover, the early short-term BR signal activation is also important for ABA-mediated salt stress tolerance. Intriguingly, the process and effect of short-term BR signal activation were covered by high concentration of ABA, implying adaptive mechanisms existed in plants to cope with varying degrees of stress.

脱落酸 (ABA) 和油菜素类固醇 (BR) 信号通路之间复杂的拮抗相互作用已被广泛记录。然而，ABA 是否或如何与植物中的 BR 协同相互作用仍有待阐明。在这里，我们报告低浓度但不高的 ABA 会增加水稻幼苗的叶片关节倾斜度，这需要功能性 BR 生物合成和信号传导。转录组分析证实，大约 60% 的低浓度 ABA 早期反应基因可以在相同方向上受 BR 调节。ABA 以快速、有限和短期的方式激活 BR 信号和 BR 生物合成调节基因OsGSR1, 在此过程中起关键作用，其表达由 ABA 通过转录因子 ABI3 轻微诱导。此外，早期短期 BR 信号激活对于 ABA 介导的盐胁迫耐受性也很重要。有趣的是，短期BR信号激活的过程和效果被高浓度的ABA所覆盖，这意味着植物中存在适应性机制来应对不同程度的胁迫。