It has been reported that low temperatures and the plant hormone abscisic acid (ABA) induce the expression of CBF/DREB1 transcription factors in vegetative tissues and seedlings of Vitis vinifera and Vitis riparia and that foliar applications of ABA to V. vinifera increase the freezing tolerance or cold-hardiness of dormant buds. However, the combined effect of ABA and low temperatures on the expression of CBF/DREB1 transcription factors and on the acquisition of freezing tolerance in dormant grapevine buds has not been investigated. Rubio et al. analysed the combined effect of ABA and low temperature treatments on the expression of CBF/DREB transcription factors and the acquisition of freezing tolerance.
The low temperature treatment and exogenous application of ABA to grapevine dormant buds increased the expression of the CBF/DREB1 transcription factors VvCBF2, VvCBF3, VvCBF4 and VvCBF6. The joint application of low temperature and ABA produced a huge increase in the expression of these transcription factors, which was greater than the sum of the increases produced by them individually, which indicates the existence of a synergistic effect between ABA and low temperatures on the activation of these transcription factors. This synergic effect was also observed on the increase in bud cold-hardiness and on the expression of antioxidant and dehydrin genes.
The synergy between ABA and low temperatures on the expression of CBF/DREB1 transcription factors VvCBF2, VvCBF3, VvCBF4 and VvCBF6 plays a key role in cold acclimatization of grapevine buds. The results highlight the importance of the combination of stimuli in the improvement of genetic and physiological responses and help us to understand the adaption of plants to complex environments.