A Novel Transcriptional Regulator HbERF6 Regulates the HbCIPK2-Coordinated Pathway Conferring Salt Tolerance in Halophytic Hordeum brevisubulatum

Halophytic Hordeum brevisubulatum is a perennial grass which has evolved many distinctive salt-adaptive mechanisms. Our previous studies indicated it could thrive under salt stress through maintaining better K + and Na + homeostasis. Stress-responsive HbCIPK2 can phosphorylate K + channel HbVGKC1 and Na + transporter HbSOS1L to prevent Na + accumulation and K + reduction, hence pathway was not detected in glycophytic plants. In this study, we cloned the inducible promoter of HbCIPK2 by genome-walking, and identified a novel transcriptional regulator HbERF6 through yeast one-hybrid screening. HbERF6 functioned as a transcription factor which can bind to the GCC-box of the HbCIPK2 promoter to activate its expression. HbERF6 transgenic lines in Arabidopsis improved salt tolerance compared with wild type, and especially induced AtCIPK24 ( SOS2 ) expression, resulting in K + /Na + homeostasis to enhance salt tolerance. All the results confirmed the inducible function of HbERF6 for CIPK genes during salt tolerance. This regulatory network that integrates transcriptional regulation and post-translation modification will unravel a novel salt stress-responsive mechanism, highlighting the value and utilization of the halophytic resource.