Enhanced tolerance to low temperature in tobacco by over-expression of a new maize protein phosphatase 2C, ZmPP2C2

Low temperature is one of the most common environmental stresses affecting plant growth and agricultural production. Serine/threonine protein phosphatases 2C (PP2Cs) have been suggested to play an important role in stress signaling. To identify potential new member of the PP2C proteins in maize and investigate its functions for stress responses, the ZmPP2C2 gene, encoding a new PP2C protein from maize roots, was cloned by RT-PCR and RACE-PCR. Its constitutive expression in roots, stems and leaves of maize seedlings was detected by RNA gel blot, and its regulation in response to cold stress was also examined. To further evaluate its function in the cold stress response, we over-expressed the ZmPP2C2 gene in tobacco under the control of the Cauliflower Mosaic Virus (CaMV) 35S promoter, and assessed a series of physiological changes in wild type and transgenic plants under low temperatures. Compared with wild type tobacco under cold stress, plants that over-expressed ZmPP2C2 displayed higher germination speed and rate, higher antioxidant enzyme (SOD, POD, CAT) activities, with lower cold-induced electrolyte leakage and malondialdehyde (MDA) contents. These results show that over-expression of ZmPP2C2 in tobacco enhanced tolerance to cold stress, suggesting that this new gene, ZmPP2C2, may act as a positive regulator of cold resistance in plants.