The NAC domain-containing protein, GmNAC6, is a downstream component of the ER stress- and osmotic stress-induced NRP-mediated cell-death signaling pathway

In the present investigation, we discovered an NAC domain-containing protein from soybean, GmNAC6 (Glycine max NAC6), to be a downstream component of the integrated pathway. Similar to NRP-A and NRP-B, GmNAC6 is induced by ER stress and osmotic stress individually, but requires both signals for full activation. Transient expression of GmNAC6 promoted cell death and hypersensitive-like responses in planta. GmNAC6 and NRPs also share overlapping responses to biotic signals, but the induction of NRPs peaked before the increased accumulation of GmNAC6 transcripts. Consistent with the delayed kinetics of GmNAC6 induction, increased levels of NRP-A and NRP-B transcripts induced promoter activation and the expression of the GmNAC6 gene.Collectively, our results biochemically link GmNAC6 to the ER stress- and osmotic stress-integrating cell death response and show that GmNAC6 may act downstream of the NRPs.Plants do not passively accept abiotic stresses, such as drought, salinity and variations of temperature, or biotic aggressors, such as viruses, bacteria, insects and fungi. To cope with these environmental stressors, plant cells have developed coordinated and integrated molecular networks for stress signal perception, transduction and adaptation mechanisms under adverse conditions of growth. In general, some adaptive cellular responses to a specific stress condition are interconnected with other environmental responses [1-3]. For instance, conditions of water stress result in both nutritional and osmotic stress, which can also be caused by salt stress. Similarly, increasing evidence in the literature has demonstrated the interconnection among the responses to pathogen attack and developmental signals [4-6]. In this complex interplay of physiological stresses, plant cells have evolved both anterograde and retrograde transduction pathways among the organelles to respond to environmental signals in an integrated and coordinated manner. One such major signaling organelle is