Expression Of A Carrot 36KD Antifreeze Protein Gene In Tobacco And The Cold Tolerance Of The Transgenic Plants

Low temperature is an important environmental stress that affects the growth and development of plants. It is the major limiting factor in agricultural productivity and quality, thus preventing crop plants from realizing their full genetic potential. Antifreeze proteins (AFPs) enable organisms to survive under cold conditions. AFPs have a great potential in improving cold tolerance of cold-sensitive plants. In order to determine whether expression of the carrot 36kD antifreeze protein gene confers improved cold properties to plant tissue, we tried to produce transgenic tobacco plants which expressed the antifreeze protein. Cold, salt, and drought induced promoter Prd29A was cloned using PCR from Arabidopsis. Two plant expression vectors based on pBI121 were constructed with CaMV35S-AFP and Prd29A-AFP. Tabacco plantlets were transformed by Agrobacterium-medicated transformation. It was demonstrated by PCR and Southern blotting that the carrot 36kD afp gene was successfully integrated into the genomes of transformed plantlets. We show here that expression of the afp gene in transgenic plants resulted in improved tolerance to cold stress. However, use of the strong constitutive 35S cauliflower mosaic virus (CaMV) promoter to drive expression of afp also resulted in growth retardation under normal growing conditions. In contrast, expression of afp driven by the stress inducible Prd29A promoter from Arabidopsis gave rise to minimal effects on plant growth while providing an increased tolerance to cold stress condition (2℃) . The results demonstrated the prospect of using Prd29 A- AFP transgenic plants in cold- stressed conditions which will in turn benefit agriculture.