The CaSBP11 gene functions as a negative regulator in pepper drought stress

The SBP-box gene family, an exclusively plant transcription factor, is critical for plant growth, development, and adaptive responses to both biotic and abiotic stresses. However, its role under non-biological stresses, specifically drought, remains overlooked in pepper plants. In our previous work, we isolated an SBP-box gene, <i>CaSBP11</i>, from the pepper genomic database. Subsequently, we employed virus-induced gene silencing, overexpression, and protein interaction experiments to investigate the function of <i>CaSBP11</i> under drought stress. Our results revealed that drought conditions significantly upregulated <i>CaSBP11</i> expression, whereas ABA treatment suppressed it. Silencing <i>CaSBP11</i> enhanced drought resistance in pepper, with increased stomatal aperture and ABA levels, and reduced stomatal density, water loss rates, and reactive oxygen species (ROS) accumulation compared to control plants. Conversely, overexpression of <i>CaSBP11</i> in <i>Nicotiana benthamiana</i> decreased drought tolerance, with <i>CaSBP11</i>-overexpressing plants showing reduced ABA sensitivity, lower stomatal aperture and ABA levels, and increased stomatal density and ROS production compared to wild-type plants. Interestingly, under non-stress conditions, core ABA signaling genes (<i>CaPP2C</i>, <i>CaPYL9</i>, <i>CaSNRK2.4</i>, <i>CaAREB</i>) exhibited lower expression in <i>CaSBP11</i>-silenced plants compared to controls, whereas this trend was reversed in <i>CaSBP11</i>-overexpressing lines (<i>NbPP2C</i>, <i>NbAREB</i>, <i>NbSNRK2.4</i>, <i>NbSRK2E</i>). Additionally, <i>CaSBP11</i> was found to interact with <i>CaPP2C</i>, <i>CaPYL9</i>, <i>CaSNRK2.4</i>, and <i>CaAREB</i> in nucleus. These data suggest that <i>CaSBP11</i> negatively regulates plant responses to drought stress and may interact with these key genes in the ABA signaling pathway to mediate this response.