Comprehensive analysis of ankyrin repeat gene family revealed SbANK56 confers drought tolerance in sorghum

Ankyrin repeat (ANK) proteins are crucial for cell growth, development, and response to hormones and environmental stress. However, there has been little research done to clarify the roles of ANK proteins in sorghum. In this study, 142 ANK genes of sorghum were identified and classified into 12 subfamilies according to the conserved domains. The cis-elements analysis revealed a substantial presence of stress-responsive elements within the promoter region of SbANK genes. After treated with drought, salt, and abscisic acid, SbANK56 showed the highest expression levels among family members by using quantitative real-time PCR (qRT-PCR) analysis. The survival rate was significantly improved by the overexpression of SbANK56 compared to wild type (WT) under drought conditions. SbANK56 overexpressing plants displayed lower malondialdehyde and higher proline contents compared to WT plants under drought conditions. Additionally, the expression levels of drought-associated genes were significantly increased in SbANK56 transgenic plants. Importantly, the analysis of natural variation in SbANK56 revealed a significant positive correlation between SbANK56_Hap4 and both its differential expression and drought stress tolerance. Taken together, our results provide some evidence for improving drought tolerance in sorghum through breeding initiatives while also advancing our knowledge of the evolutionary trends and functional mechanisms underlying ANK genes.