Dehydrating stresses trigger the accumulation of abscisic acid (ABA), a key plant stress-signaling hormone that activates Snf1-Related Kinases (SnRK2s) to mount adaptive responses. However, the regulatory circuits that terminate the SnRK2s signal relay after acclimation or post-stress conditions remain to be defined. Here, we show that the desensitization of the ABA signal is achieved by the regulation of OST1 (SnRK2.6) protein stability via the E3-ubiquitin ligase HOS15. Upon ABA signal, HOS15-induced degradation of OST1 is inhibited and stabilized OST1 promotes the stress response. When the ABA signal terminates, protein phosphatases ABI1/2 promote rapid degradation of OST1 via HOS15. Notably, we found that even in the presence of ABA, OST1 levels are also depleted within hours of ABA signal onset. The unexpected dynamics of OST1 abundance are then resolved by systematic mathematical modeling, demonstrating a desensitizing feedback loop by which OST1-induced upregulation of ABI1/2 leads to the degradation of OST1. This model illustrates the complex rheostat dynamics underlying the ABA-induced stress response and desensitization.

脱水胁迫会引发脱落酸（ABA）的积累，脱落酸是一种关键的植物胁迫信号转导激素，可激活Snf1相关激酶（SnRK2s）产生适应性反应。但是，在驯化或后应力条件之后终止SnRK2s信号继电器的调节电路仍有待定义。在这里，我们显示通过E3泛素连接酶HOS15通过调节OST1（SnRK2.6）蛋白稳定性来实现ABA信号的脱敏。根据ABA信号，抑制了HOS15诱导的OST1降解，稳定的OST1促进了应激反应。当ABA信号终止时，蛋白磷酸酶ABI1 / 2会通过HOS15促进OST1的快速降解。值得注意的是，我们发现即使存在ABA，OST1水平也会在ABA信号发作的几小时内耗尽。然后，通过系统的数学模型解决OST1丰度的意外动力学问题，这表明了脱敏反馈回路，通过该回路，OST1诱导的ABI1 / 2上调导致OST1的降解。该模型说明了ABA诱导的应激反应和脱敏的复杂变阻器动力学。