Overexpression of the GmNAC2 Gene, an NAC Transcription Factor, Reduces Abiotic Stress Tolerance in Tobacco

NAC (NAM, ATAF1, 2, and CUC2) proteins play important roles in plant development and stress responses. Glycine max NAC-like gene 2 (GmNAC2) is the first ATAF1-like NAC transcription factor identified in soybean. In this study, GmNAC-2-overexpressing tobacco lines were developed and found to be hypersensitive to drought, high salinity, and cold stress. Under abiotic stress, the transgenic tobacco leaves had higher malondialdehyde (MDA) levels compared with wild-type plants. An elevated MDA level is used frequently as an indicator of reactive oxygen species (ROS) and associated cell membrane degradation or dysfunction. To determine the mechanism of GmNAC2-mediated stress intolerance, leaf transcriptome analyses were performed comparing GmNAC2-overexpressing tobacco with wild-type tobacco. Identified downregulated genes included genes related to ROS scavenging in GmNAC2-overexpressing tobacco. These results indicate that GmNAC2 functions as a negative regulator during abiotic stress, and participates in ROS signaling pathways through modulation of the expression of genes related to ROS-scavenging.