Brassinosteroids (BRs) are known to improve salt tolerance of plants, but not in all situations. Here, we show that a certain concentration of 24‐epibrassinolide (EBL), an active BR, can promote the tolerance of canola under high‐salt stress, but the same concentration is disadvantageous under low‐salt stress. We define this phenomenon as hormonal stress‐level‐dependent biphasic (SLDB) effects. The SLDB effects of EBL on salt tolerance in canola are closely related to H₂O₂ accumulation, which is regulated by polyamine metabolism, especially putrescine (Put) oxidation. The inhibition of EBL on canola under low‐salt stress can be ameliorated by repressing Put biosynthesis or diamine oxidase activity to reduce H₂O₂ production. Genetic and phenotypic results of bri1‐9 , bak1 , bes1‐D , and bzr1‐1D mutants and overexpression lines of BRI1 and BAK1 in Arabidopsis indicate that a proper enhancement of BR signaling benefits plants in countering salt stress, whereas excessive enhancement is just as harmful as a deficiency. These results highlight the involvement of crosstalk between BR signaling and Put metabolism in H₂O₂ accumulation, which underlies the dual role of BR in plant salt tolerance.

中文翻译：

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腐胺代谢调节油菜素甾醇对低芥酸菜子和拟南芥耐盐性的两相作用。

已知油菜素类固醇（BRs）可以提高植物的耐盐性，但并非在所有情况下都如此。在这里，我们表明一定浓度的24-表油菜素内酯（EBL），一种活性BR，可以提高在高盐胁迫下的低芥酸菜子的耐性，但在低盐胁迫下，相同的浓度是不利的。我们将此现象定义为激素压力水平依赖性双相（SLDB）效应。EBL对双低油菜籽耐盐性的SLDB效应与H ₂ O ₂积累密切相关，H ₂ O ₂积累受多胺代谢，尤其是腐胺（Put）氧化的调节。可通过抑制Put生物合成或二胺氧化酶活性以减少H ₂ O ₂来改善低盐胁迫下油菜籽油对EBL的抑制作用。生产。遗传和表型结果bri1-9，BAK1，BES1-d ，和bzr1-1D突变体和过表达系BRI1和BAK1在拟南芥指示BR的一个恰当的增强信令好处植物在对抗盐胁迫，而过度的增强是一样有害为缺。这些结果突出了BR信号和Put代谢之间的串扰与H ₂ O ₂积累的关系，这是BR在植物耐盐性中的双重作用。