**Acknowledgement**

DNA binding (called NAC domain) and a C-terminal region highly divergent in sequence and length that functions as the activation domain. The NAC domain was derived from comparison of consensus sequences among NAM from Petunia, ATAF1/2 and CUC2 from Arabidopsis (Souer et al., 1996.). It comprises nearly 160 amino acid residues, divided into five subdomains (A–E) exhibiting a negative net charge and a nuclear localization signal (Xie et al., 1999; Seoet al., 2008). The subdomains A, C and D are conserved among plant species whereas B and E subdomains are variable (Ooka et al., 2003). The C- terminus har‐ bors a protein-protein interaction domain in some NAC-containing proteins while a trans‐ membrane domain is present in other transcriptional factors (Seo et al., 2008). Therefore, the NAC family is comprised by both soluble, nuclear transactivators and membrane proteins.

A Comprehensive Survey of International Soybean Research - Genetics, Physiology, Agronomy and Nitrogen

The members of the NAC gene family are involved in a variety of developmental events and defense responses, such as shoot apical meristem formation and maintenance (SAM; Aida et al., 1997; Souer et al.,1996; Weir et al., 2004), hormone signaling (Fujita et al., 2004; Xie et al., 2000), response to pathogen infection (Ren et al., 2000; Selth et al., 2005; Xie et al., 1999), leaf senescence (John et al., 1997) and response to different abiotic stresses (Hegedus et al., 2003;

The soybean NAC family is comprised by 180 putative sequences of NAC domain-contain‐ ing proteins, which display different expression profiles in response to distinct environmen‐ tal stress conditions and developmental signals (Mochida et al.,2009; Mochida et al., 2010; Wang et al., 2010). Frequently, the stress-induced expression profile of the soybean NAC genes reflects the functional profile of the encoded protein (Pinheiro et al., 2009). GmNAC6 was identified by its synergistic induction in response to a combined treatment of inducers of osmotic stress (polyethylene glycol) and ER stress (tunicamycin) and was functionally linked to the NRP-mediated cell death response (Faria et al., 2011). Transient expression of GmNAC6 promotes cell death and hypersensitive-like responses *in planta*. GmNAC6 and NRPs also share overlapping responses to biotic signals, but the induction of NRPs peaks before the increased accumulation of GmNAC6 transcripts. Consistent with the delayed ki‐ netics of GmNAC6 induction, increased levels of NRP-A and NRP-B transcripts induce pro‐ moter activation and the expression of the GmNAC6 gene. Therefore, GmNAC6 is biochemical and functionally linked to the ER stress- and osmotic stress-integrating cell

GmNAC6 encodes a 33kDa protein that belongs to the TERN (Tobacco elicitor-responsive gene encoding NAC domain protein) group of the NAC family, which is induced by elici‐ tors of the pathogen response (Ooka et al.,2003). Likewise, GmNAC6 is induced by the pathogenic bacteria *Pseudomonas syringaepatovar tomato* which elicits an incompatible interac‐ tion in soybean and by cell wall-degrading enzymes, which mimic bacterial pathogen attack. Like GmNAC6, the other components of the ER- and osmotic-stress induced cell death sig‐ naling pathway, GmERD15 and NRPs, are also induced by other biotic and abiotic signals, such drought and pathogen incompatible interactions. Therefore, the activation of the NRPmediated senescence-like response is not specific to ER stress or osmotic stress but is, rather,

death response, in which it acts downstream of the NRPs.

a shared branch of general environmental adaptive pathways.

Tran et al.,2004).

Relationships

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This research was supported by the Brazilian Government Agencies CNPq grants 559602/2009-0, 573600/2008-2 and 470878/2006-1 (to E.P.B.F.), the FAPEMIG grant CBB-APQ-00070-09, and the FINEP grant 01.09.0625.00 (to E.P.B.F.). P.A.B.R. is supported by CNPq graduate fellowships.
