Salicylic acid (SA), an essential secondary messenger for plant defence responses, plays a role in maintaining a balance (trade‐off) between plant growth and resistance induction, but the detailed mechanism has not been explored. Because the SA mimic benzothiadiazole (BTH) is a more stable inducer of plant defence than SA after exogenous application, we analysed expression profiles of defence genes after BTH treatment to better understand SA‐mediated immune induction. Transcript levels of the salicylic acid glucosyltransferase (SAGT) gene were significantly lower in BTH‐treated Nicotiana tabacum (Nt) plants than in SA‐treated Nt control plants, suggesting that SAGT may play an important role in SA‐related host defence responses. Treatment with BTH followed by SA suppressed SAGT transcription, indicating that the inhibitory effect of BTH is not reversible. In addition, in BTH‐treated Nt and Nicotiana benthamiana (Nb) plants, an early high accumulation of SA and SA 2‐O‐β‐d‐glucoside was only transient compared to the control. This observation agreed well with the finding that SAGT‐overexpressing (OE) Nb lines contained less SA and jasmonic acid (JA) than in the Nb plants. When inoculated with a virus, the OE Nb plants showed more severe symptoms and accumulated higher levels of virus, while resistance increased in SAGT‐silenced (IR) Nb plants. In addition, the IR plants restricted bacterial spread to the inoculated leaves. After the BTH treatment, OE Nb plants were slightly larger than the Nb plants. These results together indicate that SAGT has a pivotal role in the balance between plant growth and SA/JA‐mediated defence for optimum plant fitness.

中文翻译：

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水杨酸葡萄糖基转移酶在平衡生长和防御以获得最佳植物适应性方面的作用。


水杨酸（SA）是植物防御反应中重要的第二信使，在维持植物生长和抗性诱导之间的平衡（权衡）中发挥着作用，但其详细机制尚未被探索。由于SA模拟苯并噻二唑（BTH）在外源施用后是比SA更稳定的植物防御诱导剂，因此我们分析了BTH处理后防御基因的表达谱，以更好地了解SA介导的免疫诱导。 BTH 处理的烟草(Nt) 植物中水杨酸葡萄糖基转移酶( SAGT ) 基因的转录水平显着低于 SA 处理的 Nt 对照植物，表明SAGT可能在 SA 相关的宿主防御反应中发挥重要作用。 BTH 处理后 SA 抑制SAGT转录，表明 BTH 的抑制作用是不可逆的。此外，在 BTH 处理的 Nt 和本塞姆氏烟草(Nb) 植物中，与对照相比，SA 和 SA 2- O -β- d-葡萄糖苷的早期高积累只是短暂的。这一观察结果与SAGT过表达 (OE) Nb 品系中 SA 和茉莉酸 (JA) 含量低于 Nb 植物的发现非常吻合。当接种病毒时，OE Nb 植物表现出更严重的症状并积累了更高水平的病毒，而SAGT沉默（IR）Nb 植物的抗性增加。此外，IR植物限制细菌传播到接种的叶子。 BTH处理后，OE Nb植物比Nb植物稍大。 这些结果共同表明， SAGT在植物生长和 SA/JA 介导的防御之间的平衡中发挥着关键作用，以实现最佳植物适应性。