Role of salicylic acid glucosyltransferase in balancing growth and defence for optimum plant fitness

摘要

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 ( ) gene were significantly lower in BTH‐treated (Nt) plants than in SA‐treated Nt control plants, suggesting that may play an important role in SA‐related host defence responses. Treatment with BTH followed by SA suppressed transcription, indicating that the inhibitory effect of BTH is not reversible. In addition, in BTH‐treated Nt and (Nb) plants, an early high accumulation of SA and SA 2‐ ‐β‐ ‐glucoside was only transient compared to the control. This observation agreed well with the finding that ‐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 ‐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 has a pivotal role in the balance between plant growth and SA/JA‐mediated defence for optimum plant fitness.