Overexpression of a peanut NAC gene, AhNAC4, confers enhanced drought tolerance in tobacco

NAC is one of the most abundant plant-specific groups of transcription factors, which play important roles in plant growth and development regulation, as well as in biotic and abiotic stress responses. In the present study, a stress-responsive NAC gene, AhNAC4, was isolated from a cDNA library of peanut (Arachis hypogaea L.) immature seeds, and characterized for its role in drought tolerance. AhNAC4 shared high amino acid similarity with NAC proteins belonging to the ATAF subfamily. The expression analysis indicated that AhNAC4 was highly induced by drought, salinity and ABA treatments. Transient expression analysis showed the AhNAC4-GFP fusion protein was exclusively localized in the nucleus of onion epidermal cells. Transactivation assays in yeast cells demonstrated that AhNAC4 functioned as a transcription activator and its C-terminus contained the activation domain. Overexpression of AhNAC4 confers enhanced drought tolerance in transgenic tobacco plants. The improved drought tolerance was associated with more stomatal closure and higher water use efficiency. Collectively, our results indicated that AhNAC4 functions as an important regulator in response to drought stress.