A CBL-Interacting Protein Kinase TaCIPK2 Confers Drought Tolerance in Transgenic Tobacco Plants through Regulating the Stomatal Movement

<div><p>In plants, the CBL-CIPK signaling pathways play key roles in the response to abiotic stresses. However, functional studies of CIPKs in the important staple crop wheat are very rare. In this study, we identified a <i>CIPK</i> gene from wheat, designated <i>TaCIPK2</i>. Expression analysis results showed that <i>TaCIPK2</i> could be up-regulated in wheat leaves by polyethylene glycol, abscisic acid and H₂O₂ treatments. Subcellular localization analyses revealed that TaCIPK2 was present in whole wheat epidermal cells. A yeast two-hybrid assay indicated that TaCIPK2 interacted with TaCBL1, 2, 3 and 4 in vitro. Transgenic tobacco plants over-expressing <i>TaCIPK2</i> exhibited increased drought tolerance, indicated by a larger proportion of green cotyledons and higher survival rates under the osmotic and drought stress conditions compared with control plants. Additionally, physiological index analyses revealed that the transgenic tobacco plants had lower water loss rates and ion leakage, accumulated less malondialdehyde and H₂O₂, and had higher catalase and superoxide dismutase activities than the control plants. The transgenic plants also exhibited faster stomatal closure following exposure to osmotic stress conditions. The seed germination rates and stomatal aperture of <i>TaCIPK2</i>-overexpressing tobacco plants decreased after exogenous abscisic acid treatment was applied, implying that the transgenic tobacco plants were more sensitive to exogenous abscisic acid than the control plants. Our results indicate that TaCIPK2 plays a positive regulatory role in drought stress responses in transgenic tobacco plants.</p>