Ectopic Expression of Cold Responsive LlaCIPK Gene Enhances Cold Stress Tolerance in Nicotiana tabacum .

Low-temperature stress severely affects the growth, development, and geographical distribution of various crop plants, resulting in significant economic loss to producers. In a quest to identify cold-regulated genes, we constructed a cDNA suppression subtractive library from a high altitude adapted ecotype of Lepidium . We cloned a cold-induced gene Lla CIPK from the subtracted cDNA library which gave homology to Arabidopsis CIPK15 gene. The predicted 3D structure of Lla CIPK protein also showed homology with Arabidopsis CIPK protein. Quantitative real-time PCR analysis in Lepidium seedlings exposed to 6 h of cold stress shows a 3-fold increase in the expression of Lla CIPK transcript. The expression of Lla CIPK was also differentially regulated by ethylene, CaCl ₂ , ABA, and SA treatments. Ethylene and CaCl2 treatments up regulated Lla CIPK expression, whereas ABA and SA treatments down regulated the Lla CIPK expression. Transgenic plants overexpressing Lla CIPK gene under constitutive promoter show an increased level of proline and cell membrane stability. Taken together, our results suggest that the Lla CIPK contributes to the cold-response pathway in Lepidium plants.