BdDREB2A is involved in responses to heat and drought stress

Dehydration Responsive Element Binding (DREB) transcription factors play a pivotal role in abiotic stress responses. However, the functions of most Brachypodium distachyon DREB proteins remain unclear. As a model plant, B. distachyon exhibits high genomic collinearity with temperate crops. Functional characterization of BdDREBs may help to understand the molecular mechanism of Brachypodium distachyon in response to environmental stress and provide gene resources for crop improvement. Here, 58 DREB proteins, belonging to six subgroups (A1-A6), were identified at genome level. BdDREB expression was tissue-specific, e.g., seven of the 12 selected genes were predominantly expressed in roots, two genes were highly expressed in stems, and one gene was mainly expressed in leaves. These results indicate that the functions of different genes might be differentiated. Most BdDREB genes respond to abiotic stresses or exogenous phytohormones. Meanwhile, BdDREB2A was identified, and its involvement in the response to heat and drought at seedling stage was investigated by generating and analyzing RNA interference and over-expression lines. Furthermore, the underlying molecular mechanism was revealed to some extent, by performing RNA-seq, electrophoretic mobility shift assay and yeast one hybrid experiment. The results of RNA-seq and qRT-PCR indicated that BdDREB2A targets a series of downstream genes. In particular, we found that BdDREB2A specifically bound to the DRE core elements in BdERF12 and BdLEA2 promoters, indicating that they are key downstream genes of BdDREB2A in response to heat stress. Our findings enhance the understanding of DREBs, and provide clues for further research on BdDREBs.