Temporal and Spatial Regulation Analysis of Four DREBs Cloned from Phaseolus vulgaris Under Three Abiotic Stresses

DREBs are transcription factors broadly distributed in higher plants, responsive to several abiotic stresses. There is a lack of information about sequence, structure and expression of DREBs in Phaseolus vulgaris. Thus, a comprehensive analysis of four DREB genes (PvDREB2A, PvDREB5A, PvDREB5B and PvDREB6A) cloned from P. vulgaris was carried out. In silico analysis of nucleotide and deduced aminoacid sequences revealed that PvDREB2A has a repeat (GAA) that differs from others Phaseolus species and PvDREB6A has a signal peptide for chloroplast localization. Expression levels of the four genes in plants under drought, salt and cold treatments were obtained by RT-qPCR. In control conditions, their transcripsts were high in leaves and roots and very low in stems. Under stress, the four genes presented low changes in leaves, being more responsive in stems and roots. PvDREB2A was repressed in all tissues under cold stress, but was up-regulated in stems and roots under drought and salt treatment. PvDREB5A, PvDREB5B and PvDREB6A were induced in stems and roots under all stresses. The dinamics of gene regulation was analyzed from 12 to 96 hours of drought stress and after re-hydration. In leaves, they are repressed at the first 12h; then a shift was detected at 24 and 48h, decreasing again with dorught severity. In roots, a pattern of complementarity was observed mainly for PvDREB5A and PvDREB5B, but also for PvDREB6A, the most expressed gene during the stress. The PvDREB2B pattern was opposite from PvDREB6A and is suggested to have a role after re-hydration of plants.