Genome-wide identification of calmodulin-binding protein 60 gene family and function of SmCBP60A1 in eggplant response to salt stress

Calmodulin-binding protein 60 (CBP60) members are essential in plant response to pathogen attack, and growth and development. Salt stress is one of the main abiotic stress affecting growth, development, and production in plants. However, the functions of CBP60 gene family members in plant response to abiotic stresses, especial salt stress, are largely unknown. Herein, we identified 10 CBP60 members in the eggplant (Solanum melongena) genome (SmCBP60) and analyzed their corresponding sequences and structures to explore their expression patterns. Further analysis showed that all 10 SmCBP60 proteins located in nuclei in the epidermic cells of Nicotiana benthamiana leaves, and the transcript expression levels of SmCBP60s including SmCBP60A1, SmCBP60A3, SmCBP60C1, and SmCBP60C2 were significantly up-regulated in the root of eggplant treated with salt stress. The silencing of SmCBP60A1 by virus-induced gene silencing enhanced eggplant susceptibility to salt stress, accompanied by down-regulation of transcript expression levels of salt stress defense-related marker genes Dehydrin 1 (SmDHN1), SmABA8'HO, SmDHNX1, and SmGSTU10, and decreased the content of proline and catalase (CAT) enzyme activity. These results suggest that SmCBP60A1 acts as a positive regulator in eggplant response to salt stress, and may be valuable for the improvement of eggplant varieties to improve its tolerance to salt stress.