Expression of the Arabidopsis DREB1A gene in transgenic chrysanthemum enhances tolerance to low temperature

The gene DREB1A, encoding a stress-inducible transcription factor, driven by the cauliflower mosaic virus 35S (CaMV) promoter or by the stress-inducible rd29A promoter, was transferred into chrysanthemum plants [Dendranthema grandiflorum (Ramat.) Kitamura] cv. 'Fall Color' by Agrobacterium-mediated transformation. Integration of the target gene, DREB1A was confirmed by PCR and Southern blotting. When exposed to 2 degrees C, expression of DREB1A was enhanced in the roots of young transgenic 35S:DREB1A plant lines, and induced in transgenic rd29A:DREB1A lines. Electrolyte leakage in leaves of rd29A:DREB1A plant lines was significantly lower than in 35S:DREB1A lines. Compared to control plants, superoxide dismutase activities and proline contents increased slowly in transgenic plants at the start of the cold stress treatment and remained at high levels during later periods, especially in rd29A:DREB1A transgenic lines. Young plants of the rd29A:DREB1A line could tolerate -8 degrees C for 12 h, with a survival rate of 37.5 %. No survival was observed in 35S:DREB1A lines or in wild- type plants. These results indicate that a combination of the stress-inducible rd29A promoter and the DREB1A gene enhanced the tolerance of ground-cover chrysanthemum plants to cold stress through a transgenic approach.