Computational characterization of structural and functional roles of DREB1A, DREB1B and DREB1C in enhancing cold tolerance in rice plant.

Rice serves as the major food for almost half of the world population. Because of its origin in the tropical and subtropical area, rice is more sensitive towards cold stress. Three homologs of DREB1, namely DREB1A, DREB1B and DREB1C are induced Queryduring cold stress and after binding with GCC-box in the promoter region of the target gene, they enhance cold tolerance in rice plants. Though the majority of DREBs bind GCC-box, the degree of activation varies among DREBs. The protein encoded via these three transcription factors contains a common domain, namely AP2/ERF. In silico method was utilised to predict 3D structure of each AP2/ERF domain. The molecular dynamic analysis suggests, under the normal environmental condition, in each AP2/ERF domain, a positive correlation exists between β-strands and the movement of C-α is constrained. However, during cold stress, when AP2/ERF domain binds with GCC-box present in the promoter region of the target gene, mean pressure of each three AP2/ERF domain gets lowered and final potential energy increases. A positive correlation between β-strands gets disrupted and C-α experiences random movement suggesting enhanced activity of DREB1A, DREB1B and DREB1C during cold stress and enhancement of cold tolerance in plants. Further, MM/PBSA calculations for protein-DNA affinities reveal that, due to lack of α2 in DREB1C, the binding affinity of GCC-box with AP2/ERF domain of DREB1A > DREB1B > DREB1C. Thus, due to a better binding affinity with GCC-box, DREB1A and DREB1B can be utilised in near future for increasing cold tolerance of rice plant and increasing yield.