title: GmNAC30 and GmNAC81 integrate the endoplasmic reticulum stress- and osmotic stress-induced cell death responses through a vacuolar processing enzyme.
abstract: Prolonged endoplasmic reticulum and osmotic stress synergistically activate the stress-induced N-rich protein-mediated signaling that transduces a cell death signal by inducing GmNAC81 (GmNAC6) in soybean. To identify novel regulators of the stress-induced programmed cell death (PCD) response, we screened a two-hybrid library for partners of GmNAC81. We discovered another member of the NAC (NAM-ATAF1,2-CUC2) family, GmNAC30, which binds to GmNAC81 in the nucleus of plant cells to coordinately regulate common target promoters that harbor the core cis-regulatory element TGTG[TGC]. We found that GmNAC81 and GmNAC30 can function either as transcriptional repressors or activators and cooperate to enhance the transcriptional regulation of common target promoters, suggesting that heterodimerization may be required for the full regulation of gene expression. Accordingly, GmNAC81 and GmNAC30 display overlapping expression profiles in response to multiple environmental and developmental stimuli. Consistent with a role in PCD, GmNAC81 and GmNAC30 bind in vivo to and transactivate hydrolytic enzyme promoters in soybean protoplasts. A GmNAC81/GmNAC30 binding site is located in the promoter of the caspase-1-like vacuolar processing enzyme (VPE) gene, which is involved in PCD in plants. We demonstrated that the expression of GmNAC81 and GmNAC30 fully transactivates the VPE gene in soybean protoplasts and that this transactivation was associated with an increase in caspase-1-like activity. Collectively, our results indicate that the stress-induced GmNAC30 cooperates with GmNAC81 to activate PCD through the induction of the cell death executioner VPE.
authors.affiliation: Departamento de Bioquímica e Biologia Molecular/Bioagro, Instituto Nacional de Ciência e Tecnologia em interacoes planta-praga, Universidade Federal de Viçosa, 36570-000 Viçosa MG, Brazil.
authors.forename: Giselle C
authors.initials: GC
authors.lastname: Mendes
authors.forename: Pedro A B
authors.initials: PA
authors.lastname: Reis
authors.forename: Iara P
authors.initials: IP
authors.lastname: Calil
authors.forename: Humberto H
authors.initials: HH
authors.lastname: Carvalho
authors.forename: Francisco J L
authors.initials: FJ
authors.lastname: Aragão
authors.forename: Elizabeth P B
authors.initials: EP
authors.lastname: Fontes
mesh_terms: D016923:Cell Death / Q000502:physiology*; D047369:Chromatin Immunoprecipitation; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D059865:Endoplasmic Reticulum Stress / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D018613:Microscopy, Confocal; D064587:Osmoregulation / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction; D013025:Glycine max / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D014157:Transcription Factors; D003546:Cysteine Endopeptidases; C089278:vacuolar processing enzyme
keywords: ER stress; NAC transcriptional factors; abiotic stresses; cell death signaling