title: Overexpression of PaNAC03, a stress induced NAC gene family transcription factor in Norway spruce leads to reduced flavonol biosynthesis and aberrant embryo development.
abstract: The NAC family of transcription factors is one of the largest gene families of transcription factors in plants and the conifer NAC gene family is at least as large, or possibly larger, as in Arabidopsis. These transcription factors control both developmental and stress induced processes in plants. Yet, conifer NACs controlling stress induced processes has received relatively little attention. This study investigates NAC family transcription factors involved in the responses to the pathogen Heterobasidion annosum (Fr.) Bref. sensu lato.
  
  
  
  The phylogeny and domain structure in the NAC proteins can be used to organize functional specificities, several well characterized stress-related NAC proteins are found in III-3 in Arabidopsis (Jensen et al. Biochem J 426:183-196, 2010). The Norway spruce genome contain seven genes with similarity to subgroup III-3 NACs. Based on the expression pattern PaNAC03 was selected for detailed analyses. Norway spruce lines overexpressing PaNAC03 exhibited aberrant embryo development in response to maturation initiation and 482 misregulated genes were identified in proliferating cultures. Three key genes in the flavonoid biosynthesis pathway: a CHS, a F3'H and PaLAR3 were consistently down regulated in the overexpression lines. In accordance, the overexpression lines showed reduced levels of specific flavonoids, suggesting that PaNAC03 act as a repressor of this pathway, possibly by directly interacting with the promoter of the repressed genes. However, transactivation studies of PaNAC03 and PaLAR3 in Nicotiana benthamiana showed that PaNAC03 activated PaLAR3A, suggesting that PaNAC03 does not act as an independent negative regulator of flavan-3-ol production through direct interaction with the target flavonoid biosynthetic genes.
  
  
  
  PaNAC03 and its orthologs form a sister group to well characterized stress-related angiosperm NAC genes and at least PaNAC03 is responsive to biotic stress and appear to act in the control of defence associated secondary metabolite production.
authors.affiliation: Department of Forest Mycology and Plant Pathology, Uppsala Biocenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.|Department of Chemistry and Biotechnology, Uppsala Biocenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Dalman
authors.affiliation: KTH Biotechnology, Royal Institute of Technology, AlbaNova University Centre, Stockholm, Sweden.
authors.forename: Julia Johanna
authors.initials: JJ
authors.lastname: Wind
authors.affiliation: Department of Forest Mycology and Plant Pathology, Uppsala Biocenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Miguel
authors.initials: M
authors.lastname: Nemesio-Gorriz
authors.affiliation: Department of Biochemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.|Department of Microbiology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa.
authors.forename: Almuth
authors.initials: A
authors.lastname: Hammerbacher
authors.affiliation: Department of Forest Mycology and Plant Pathology, Uppsala Biocenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Karl
authors.initials: K
authors.lastname: Lundén
authors.affiliation: KTH Biotechnology, Royal Institute of Technology, AlbaNova University Centre, Stockholm, Sweden.
authors.forename: Ines
authors.initials: I
authors.lastname: Ezcurra
authors.affiliation: Department of Forest Mycology and Plant Pathology, Uppsala Biocenter, Swedish University of Agricultural Sciences, Uppsala, Sweden. Malin.Elfstrand@slu.se.|Department of Forest Mycology and Plant Pathology, SLU, PO. Box 7026, Uppsala, 75007, Sweden. Malin.Elfstrand@slu.se.
authors.forename: Malin
authors.identifier: 0000-0002-0214-5284
authors.initials: M
authors.lastname: Elfstrand
mesh_terms: D005419:Flavonoids / Q000096:biosynthesis*; D018506:Gene Expression Regulation, Plant; D005810:Multigene Family; D009664:Norway; D010802:Phylogeny; D028222:Picea / Q000145:classification / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D005419:Flavonoids; D010940:Plant Proteins; D014157:Transcription Factors; C041477:3-hydroxyflavone
keywords: ATAF (Arabidopsis transcription activation factor); ATAF1; Bark; CUC (cup-shaped cotyledon)]; Flavonoids; Homeodomain proteins; Leucoanthocyanidin reductase (LAR); NAC [for NAM (no apical meristem); Picea; Resistance to Heterobasidion annosum; Transcriptome