Expression Profile of Three DREB (Dehydration Responsive Element-Binding) Genes under Abiotic Stresses in Common Bean (Phaseolus vulgaris L.)

Common bean (Phaseolus vulgaris L.) is strongly affected by drought seasons, high soil salinity, heating or cold, factors that lower its productivity. Several studies have been focused to understand gene regulation under such stresses. DREBs (dehydration responsive element-binding) are key factors capable to bind and regulate expression of several stress responsive genes. Few reports are available for DREB genes in common bean. Three PvDREBs (PvDREB1, PvDREB2A and PvDREB6B) were analyzed under drought (PEG 10%), salt (200 mM NaCl), cold (4^oC) and abscisic acid (ABA 100 µM) treatments in different time points in a drought tolerant genotype, BAT 477. A spatial scale expression analysis was performed including more genotypes: the Andean Jalo EEP558 (drought susceptible); and Mesoamericans BAT 93 (tolerant), IAC-Carioca 80SH (moderately tolerant) and RAB 96 (susceptible). Our qPCR results showed PvDREB1 was strongly activated (up to 8,000 fold-change for BAT 477) in all treatments in roots, stems and leaves. Low basal transcript levels were found to this gene in untreated plants, but with strong activation immediately after stress induction. PvDREB2A was induced by drought in stems (8 fold-change) and PvDREB6B showed activation by drought in roots (2 fold-change) and leaves (up to 3.4 fold-change). PvDREB1 seems to be ABA-dependent and PvDREB2A and PvDREB6B may be independent to this hormone. Expression levels were different among genotypes and revealed that the tolerant ones were more responsive than the susceptible ones. These genes are strong candidates for breeding strategies for tolerance to drought and other abiotic stresses.