Genome-Wide Identification and Expression Analysis of the CsCAMTA Gene Family in Tieguanyin Tea Plants Under Heat Stress

Tieguanyin (Camellia sinensis cv. Tieguanyin) is an important oolong tea cultivar in China, and heat stress has become a major environmental constraint affecting its growth and productivity. Calmodulin-binding transcription activators (CAMTAs) are important transcription factors involved in calcium/calmodulin-mediated signaling and plant responses to environmental stresses. However, systematic knowledge of the CAMTA gene family in Tieguanyin remains limited. In this study, 20 CsCAMTA genes were identified from the Tieguanyin genome and characterized based on their physicochemical properties, phylogenetic relationships, conserved motifs, gene structures, chromosomal distribution, collinearity, promoter cis-acting elements, and functional annotation. The 20 CsCAMTA genes were unevenly distributed across eight chromosomes, and collinearity analysis suggested that segmental duplication may have contributed to the expansion of this gene family. Conserved motif and domain analyses indicated that CsCAMTA proteins retained typical structural features of CAMTA transcription factors, including CG-1, ANKYR, TIG, and CaMBD/IQ-related regions. Promoter analysis showed that CsCAMTA genes harbored multiple cis-acting elements related to hormone responsiveness, stress response, light response, and growth regulation. Furthermore, qRT-PCR analysis of 18 representative CsCAMTA genes under 40 °C heat treatment revealed distinct temporal expression patterns, suggesting that different CsCAMTA members may respond to heat stress at different stages. Several genes, such as CsCAMTA2, CsCAMTA10, and CsCAMTA16, showed marked transcriptional changes and may represent candidate heat-responsive genes in Tieguanyin. These results provide a systematic overview of the CsCAMTA gene family and lay a foundation for further functional studies of heat stress responses in Tieguanyin.