The durum wheat NAC transcription factor TtNAC2A enhances drought stress tolerance in Arabidopsis

Plant specific NAC transcription factors play diverse roles in plant development and stress responses. However, their biological roles in crop plants such as wheat remain poorly described. Here, we report the isolation and functional characterization of novel durum wheat TtNAC2A gene which acts as a transcription activator in yeast. Expression profiling analyses revealed that TtNAC2A gene is expressed in several wheat tissues and at different stages of seed development. Moreover, TtNAC2A was up-regulated in leaves and roots after exposure to salt, PEG and exogenous abscisic acid treatments, and this up-regulation was confirmed by functional promoter analysis in Arabidopsis. Furthermore, transgenic Arabidopsis plants overexpressing TtNAC2A showed enhanced drought tolerance and hypersensitivity to ABA. This phentotype was accompanied by a greater water retention capacity, attenuated oxidative stress, lower electrolyte leakage and higher proline contents, compared to wild type plants. The TtNAC2A-mediated drought tolerance also corroborated with an activation of a subset of stress-responsive genes, including AtRD22, AtRD29A and AtRD29B. Thus, TtNAC2A functions as a positive regulator of drought stress tolerance and constitutes an attractive candidate for stress breading in wheat crops.