S-acylated and nucleus-localized SALT OVERLY SENSITIVE3/CALCINEURIN B-LIKE4 stabilizes GIGANTEA to regulate Arabidopsis flowering time under salt stress

背景回顾：The precise timing of flowering in adverse environments is critical for plants to secure reproductive success. 

主要发现：We report a mechanism in Arabidopsis (Arabidopsis thaliana) controlling the time of flowering by which the S-acylation-dependent nuclear import of the protein SALT OVERLY SENSITIVE3/CALCINEURIN B-LIKE4 (SOS3/CBL4), a Ca2+-signaling intermediary in the plant response to salinity, results in the selective stabilization of the flowering time regulator GIGANTEA inside the nucleus under salt stress, while degradation of GIGANTEA in the cytosol releases the protein kinase SOS2 to achieve salt tolerance. 

结果1-SOS3的S-酰化：S-acylation of SOS3 was critical for its nuclear localization and the promotion of flowering, but partly dispensable for salt tolerance. 

结果2-SOS3-CO：SOS3 interacted with the photoperiodic flowering components GIGANTEA and FLAVIN-BINDING, KELCH REPEAT, F-BOX1 and participated in the transcriptional complex that regulates CONSTANS to sustain the transcription of CO and FLOWERING LOCUS T under salinity. 

结论：Thus, the SOS3 protein acts as a Ca2+- and S-acylation-dependent versatile regulator that fine-tunes flowering time in a saline environment through the shared spatial separation and selective stabilization of GIGANTEA, thereby connecting two signaling networks to co-regulate the stress response and the time of flowering.

 摘 要 

在逆境下准时开花对于植物保证生殖成功至关重要。本文中，作者报道了一个拟南芥中控制开花时间的分子机制，S-酰化依赖性的核导入蛋白SOS3/CBL4，即植物盐胁迫响应中的钙离子信号转导中介，导致盐胁迫下核内开花时间调控因子GIGANTEA的选择性稳定，而GIGANTEA在胞质中的降解会释放蛋白激酶SOS2，从而产生盐耐受性。SOS3蛋白的S-酰化对于其核定位以及开花促进至关重要，但是对于盐耐受性来说则在某种程度上来说是可有可无的。SOS3与光周期开花组分GIGANTEA和FKF1互作，参与形成转录复合物调控CO基因的表达，以维持CO和FT在盐胁迫条件下的表达。因此，SOS3蛋白作为一个钙离子和S-酰化依赖性多功能调节因子，在盐生境下通过GIGANTEA蛋白的空间分离和选择性稳定，精确调控植物的开花时间，因而连通了两个信号转导网络，共同调控胁迫响应和开花时间。