CnbHLH130 positively regulates salt tolerance through CnCBL10-CnCIPK4 mediated SOS pathway in Campeiostachys nutans

Campeiostachys nutans, a dominant perennial grass in the Qinghai-Tibet Plateau, exhibits high tolerance to salt stress. The Salt Overly Sensitive (SOS) pathway is key to plant salt stress tolerance. However, the pivotal role of the SOS pathway in response to salt stress in C. nutans remains unknown. Here, we identified CnbHLH130 as a novel transcriptional activator of CnCBL10, directly binds to the G-box motif in the promoter. CnbHLH130 responds to salt stress and positively regulate salt tolerance in rice and C. nutans. Interestingly, we found CnCBL10 and CnCIPK4 interact with CnbHLH130 by a Y2H screening assay. The interactions were confirmed by split-luciferase complementation (split-LUC), Pull-down, Co-immunoprecipitation (Co-IP) and bimolecular fluorescence complementation (BiFC) assays. Moreover, CnbHLH130 enhanced the interaction between CnCBL10 and CnCIPK4, which further phosphorylate and activate Na+/H+ antiporter CnSOS1 to exclude excess cytosolic Na+ from cells in the shoots. Genetic evidence showed that CnCBL10, CnCIPK4 and CnbHLH130 coordinately regulates salt tolerance in plants. In summary, this study demonstrated that CnbHLH130 acts as a novel core component and transcriptional activator regulating CnCBL10-CnCIPK4 mediated SOS pathway, thus conferring to the salt tolerance in C. nutans. This work advanced our understandings of how an alpine plant greatly survived in the Qinghai-Tibet Plateau by concise regulation of the SOS pathway in response to salt stress. 28-day-old C. nutans seedlings treated with or without 200 mM salt treatment for 5 d were used for RNA-seq analysis.