The molecular cloning and functional characterization of ChNAC1, a NAC transcription factor in Cerasus humilis

Plant-specific NAM, ATAF, and CUC (NAC) transcription factors (TFs) play clear roles in plant development and abiotic stress responses. Chinese dwarf cherry (Cerasus humilis) is an economically important shrub, that has strong resistance to drought. In this study, we isolated and functionally characterized a novel NAC TF from C. humilis. The ChNAC1 ORF contained 894 nucleotides, encoding 297 amino acid residues. ChNAC1 amino acid sequences had the highest similarity with homologous petunia (Petunia hybrida) and tomato (Solanum lycopersicum) NAM proteins. The ChNAC1 transcripts were most abundant in the leaves of seedlings and significantly up-regulated by drought stress. The nuclear localization and transcriptional activity of the C-terminal domain further confirmed that ChNAC1 functions as a TF. Yeast two-hybrid results showed that ChNAC1 can homodimerize in yeast cells. Next, we transformed ChNAC1 into wild-type Arabidopsis thaliana and found that the ectopic expression of ChNAC1 increased chlorophyll, water, proline, and protein contents as well as higher peroxidase (POD) and superoxide dismutase (SOD) activities while decreasing electrolyte conductivity and reactive oxygen species (ROS) contents compared to wild-type and mutant lines. Further, overexpression of ChNAC1 positively regulated ABA-responsive genes under drought stress and increased ABA sensitivity during root growth. Collectively, these results demonstrate the key role of ChNAC1 in drought stress tolerance.