Genome-wide analysis of the CCT gene family and functional characterization of SlCCT6 in response to drought stress in tomato.

CCT transcription factors are important for photoperiod and abiotic stress regulation in Arabidopsis and rice. However, the CCT gene family has not been reported in tomato. Here, we systematically analyzed this. Thirty-one SlCCT genes were identified and divided into five groups (CMF, TIFY, PRR, S8, and COL), with members unevenly distributed across 12 chromosomes and the third chromosome exhibiting the most distribution. SlCCT was found to interact with an interacting protein (SlGI), transcription factor (MYB), and non-coding RNA (sly-miR156-5p) to jointly regulate the tomato stress response. cis-Acting element analysis of the SlCCT promoter region indicated large stress- and hormone-response elements in this family. Real-time PCR results indicated that SlPRR subfamily genes respond to various abiotic stresses and hormones. Tissue expression analysis revealed that several PRR subfamily genes are highly expressed in flowers, and subcellular localization analysis indicated an SlCCT6 nuclear location. Notably, SlCCT6 expression was significantly induced by drought, and its silencing reduced drought stress tolerance. Moreover, SlCCT6 overexpression enhanced tomato drought resistance by increasing antioxidant enzyme activity and activating stress-related genes, whereas SlCCT6 knockout decreased drought resistance. In conclusion, this provides valuable insights for future research on SlCCT functions.