StCIPK2–StCBL11 complex negatively modulates drought tolerance in potato plant by regulating oxidative resistance and ABA biosynthesis

Calcineurin B-like (CBL) proteins and CBL-interacting protein kinases (CIPK) play essential roles in regulating plant responses to various stresses. However, the molecular and functional properties of CBL–CIPK in drought response have been rarely characterised in potato plants. In this study, we subjected the potato ‘Atlantic’ cultivar (wild type [WT], ami-StCIPK2, and overexpression [OE] lines) to stress through ABA treatment, osmotic stress, and drought stress. We characterised the potato CBL-interacting protein kinase StCIPK2. We measured the relative water content, superoxide dismutase and peroxidase activities, and H2O2, proline, malondialdehyde, and soluble sugar levels as these are indices of drought tolerance. We estimated the stomatal movement and root growth phenotype (length of plant roots). Finally, we performed a protein interaction assay. We found that StCIPK2 was effectively induced by multiple stressors and is highly homologous to AtCIPK1. Accordingly, StCIPK2 overexpression decreased drought tolerance and ABA sensitivity in potato, whereas StCIPK2 knock-down increased these responses. Moreover, StCIPK2 interacted with StCBL11 on the plasma membrane. Additionally, the drought tolerance indices showed that drought resistance and ABA sensitivity did not differ between StCBL11-OE and WT plants, and StCBL11 overexpression in StCIPK2 knock-down plants negated their drought resistance and ABA sensitivity. Overall, this study shows that the StCBL11–StCIPK2 module negatively regulates drought stress tolerance in potatoes, and it could be used in novel ways to improve stress regulation in potato plant.