GhSCL4 Acts as a Positive Regulator in Both Transgenic Arabidopsis and Cotton During Salt Stress

GRAS transcription factors play important roles in plant abiotic stress response, but their characteristics and functions in cotton have not been fully investigated. A cotton SCL4/7 subgroup gene in the GRAS family, GhSCL4, was found to be induced by NaCl treatments. Nuclear localization and transactivation activity of GhSCL4 indicate its potential role in transcriptional regulation. Transgenic Arabidopsis thaliana over-expressing GhSCL4 showed enhanced resistance to salt and osmotic stress. What’s more, the transcript levels of salt stress-induced genes (AtNHX1 and AtSOS1) and oxidation-related genes (AtAPX3 and AtCSD2) were more highly induced in the GhSCL4 over-expression lines than in wild type after salt treatment. Furthermore, silencing of GhSCL4 resulted in reduced salt tolerance in cotton caused by reactive oxygen species (ROS) enrichment under salt treatment, and antioxidant enzyme activities were accordingly significantly reduced in GhSLC4-silenced lines. These results indicated that GhSCL4 enhances salt tolerance of cotton by detoxifying ROS. In addition, the transient expression assay confirmed an interactive relationship between GhSCL4 and GhCaM7, which indicated that salt tolerance conferred by GhSCL4 might be associated with salt-induced Ca2+/CaM7-mediated signaling. Taken together, GhSCL4 acts as a positive regulator in cotton during salt stress that is potentially useful for engineering salt-tolerant cotton.