Transcription Factor CaSBP12 Negatively Regulates Salt Stress Tolerance in Pepper (Capsicum annuum L.)

SBP-box (Squamosa-promoter binding protein) genes are a type of plant-specific transcription factor and play important roles in plant growth, signal transduction, and stress response. However, little is known about the role of pepper SBP-box transcription factor genes in response to abiotic stress. Here, one of the pepper SBP-box gene, CaSBP12, was selected and isolated from pepper genome database in our previous study. The CaSBP12 gene was induced under salt stress. Silencing the CaSBP12 gene enhanced pepper plant tolerance to salt stress. The accumulation of reactive oxygen species (ROS) of the detached leaves of CaSBP12-silenced plants was significantly lower than that of control plants. Besides, the Na⁺, malondialdehyde content, and conductivity were significantly increased in control plants than that in the CaSBP12-silenced plants. In addition, the CaSBP12 over-expressed Nicotiana benthamiana plants were more susceptible to salt stress with higher damage severity index percentage and accumulation of ROS as compared to the wild-type. These results indicated that CaSBP12 negatively regulates salt stress tolerance in pepper may relate to ROS signaling cascades.