The over-expression of calmodulin from Antarctic notothenioid fish increases cold tolerance in tobacco

Abstract Genes involved in the calcium signalling pathway have a relationship with cold tolerance in many plants. The primary reaction to many different environmental stresses is an increase in the cytoplasmic Ca 2 + concentration. Such variations in the Ca 2 + concentration could change the activity of Ca 2 + -dependent protein functions, further regulating the expression of stress-related genes; therefore, the Ca 2 + signalling pathway is involved in the biological stress reaction. The expression of the calcium-modulated protein gene, calmodulin, in Antarctic notothenioid fish ( Dissostichus mawsoni ) accounts for 0.23% of all transcripts, which is a very high level of expression in this cold-water fish. To elucidate the function of calmodulin ( CaM ) from Antarctic notothenioid fishes, we introduced the calmodulin ( CaM ) gene into tobacco plants using a viral vector based on pea early browning virus (PEBV). RT-PCR and Western blot results confirmed that the CaM gene was over-expressed in tobacco. Under low-temperature stress, the CaM transgenic plants exhibited faster growth than wild-type plants. The physiological and biochemical effects of the high-level expression of CaM in tobacco were analysed, and the changes in the electrolyte leakage activity and malondialdehyde content showed that CaM over-expression in tobacco increased the cold tolerance of the plants. These results demonstrate that CaM can possibly be used to enhance the low-temperature tolerance of plants.