Abiotic stress factors, such as drought and salinity, are known to negatively affect plant growth and development. To cope with these adverse conditions, plants have utilized certain defense mechanisms involved in various aspects, including morphological, biochemical and molecular alterations. Particularly, a great deal of evidence for the biological importance of the plant-specific NAM, ATAF1/2, CUC2 (NAC) transcription factors (TFs) in plant adaptation to abiotic stress conditions has been reported. A previous in planta study conducted by our research group demonstrated that soybean (Glycine max) GmNAC085 mediated drought resistance in transgenic Arabidopsis plants. In this study, further characterization of GmNAC085 function in association with salt stress was performed. The findings revealed that under this condition, transgenic soybean plants overexpressing GmNAC085 displayed better germination rates than wild-type plants. In addition, biochemical and transcriptional analyses showed that the transgenic plants acquired a better defense system against salinity-induced oxidative stress, with higher activities of antioxidant enzymes responsible for scavenging hydrogen peroxide or superoxide radicals. Higher transcript levels of several key stress-responsive genes involved in the proline biosynthetic pathway, sodium ion transporter and accumulation of dehydrins were also observed, indicating better osmoprotection and more efficient ion regulation capacity in the transgenic lines. Taken together, these findings and our previous report indicate that GmNAC085 may play a role as a positive regulator in plant adaptation to drought and salinity conditions.

Climate change has made abiotic stresses such as drought and salinity bigger threats to ecosystem and global food security. In response to unfavorable conditions, physiological, biochemical and molecular activities in plants are altered. Particularly, various members of NAC (NAM, ATAF1/2, CUC2) transcriptional factor family have been reported to be the key regulators in modulating multiple biological processes of plant responses to osmotic stress conditions caused by drought and salinity. Previously, transgenic studies have shown the positive regulatory role of GmNAC085, a NAC transcription factor from soybean (Glycine max), in plant resistance against drought stress. Therefore, in this study, we extended the investigation on its contribution to salinity stress. According to our RT-qPCR analyses, expression of several important stress-related genes was significantly induced in the transgenic soybean plants in comparison with the wild-type plants, including antioxidant enzyme-encoding genes (GmSOD, GmAPX and GmCAT), sodium-proton antiporter encoding gene (GmNHX1) and proline metabolic gene (GmP5CS). Furthermore, biochemical results were also in agreement with the molecular data, with enhanced antioxidant enzyme activities of peroxidase and catalase, and in couple with lower cellular content of the reactive oxygen species hydrogen peroxide in the transgenic plants. Taken these altogether, the transgenic plants might acquire advantages in dealing with oxidative stress using enzymes and proline, as well as cellular Na+ removal under salinity stress conditions. Therefore, underlying mechanisms of GmNAC085 associated with salinity stress should be fully elaborated to find out its potential utility in crop improvement.