To adapt to changing environments, plants have evolved elaborate regulatory mechanisms balancing their growth with stress responses. It is currently unclear whether and how the tryptophan (Trp), the growth-related hormone auxin, and the stress hormone abscisic acid (ABA) are coordinated in this trade-off. Here, we show that tryptophan synthase β subunit 1 (TSB1) is involved in the coordination of Trp and ABA, thereby affecting plant growth and abiotic stress responses. Plants experiencing high salinity or drought display reduced TSB1 expression, resulting in decreased Trp and auxin accumulation and thus reduced growth. In comparison with the wild type, amiR-TSB1 lines and TSB1 mutants exhibited repressed growth under non-stress conditions but had enhanced ABA accumulation and stress tolerance when subjected to salt or drought stress. Furthermore, we found that TSB1 interacts with and inhibits β-glucosidase 1 (BG1), which hydrolyses glucose-conjugated ABA into active ABA. Mutation of BG1 in the amiR-TSB1 lines compromised their increased ABA accumulation and enhanced stress tolerance. Moreover, stress-induced H₂O₂ disrupted the interaction between TSB1 and BG1 by sulfenylating cysteine-308 of TSB1, relieving the TSB1-mediated inhibition of BG1 activity. Taken together, we revealed that TSB1 serves as a key coordinator of plant growth and stress responses by balancing Trp and ABA homeostasis.

为了适应不断变化的环境，植物已经进化出复杂的调节机制来平衡它们的生长和应激反应。目前尚不清楚色氨酸 (Trp)、生长相关激素生长素和应激激素脱落酸 (ABA) 是否以及如何在这种权衡中协调。在这里，我们表明色氨酸合酶 β 亚基 1 (TSB1) 参与了色氨酸和 ABA 的协调，从而影响植物生长和非生物胁迫反应。经历高盐度或干旱的植物显示TSB1表达减少，导致色氨酸和生长素积累减少，从而减少生长。与野生型相比，amiR-TSB1系和TSB1突变体在非胁迫条件下表现出抑制生长，但在受到盐或干旱胁迫时具有增强的ABA积累和胁迫耐受性。此外，我们发现 TSB1 与 β-葡萄糖苷酶 1 (BG1) 相互作用并抑制它，后者将葡萄糖结合的 ABA 水解为活性 ABA。amiR-TSB1系中BG1的突变损害了它们增加的 ABA 积累和增强的胁迫耐受性。此外，应激诱导的 H ₂ O ₂通过对 TSB1 的 308 半胱氨酸进行亚磺酰化破坏了 TSB1 和 BG1 之间的相互作用，从而减轻了 TSB1 介导的 BG1 活性抑制。总之，我们揭示了 TSB1 通过平衡 Trp 和 ABA 稳态作为植物生长和应激反应的关键协调者。