title: The barley HvNAC6 transcription factor affects ABA accumulation and promotes basal resistance against powdery mildew.
abstract: Barley HvNAC6 is a member of the plant-specific NAC (NAM, ATAF1,2, CUC2) transcription factor family and we have shown previously that it acts as a positive regulator of basal resistance in barley against the biotrophic pathogen Blumeria graminis f. sp. hordei (Bgh). In this study, we use a transgenic approach to constitutively silence HvNAC6 expression, using RNA interference (RNAi), to investigate the in vivo functions of HvNAC6 in basal resistance responses in barley in relation to the phytohormone ABA. The HvNAC6 RNAi plants displayed reduced HvNAC6 transcript levels and were more susceptible to Bgh than wild-type plants. Application of exogenous ABA increased basal resistance against Bgh in wild-type plants, but not in HvNAC6 RNAi plants, suggesting that ABA is a positive regulator of basal resistance which depends on HvNAC6. Silencing of HvNAC6 expression altered the light/dark rhythm of ABA levels which were, however, not influenced by Bgh inoculation. The expression of the two ABA biosynthetic genes HvNCED1 and HvNCED2 was compromised, and transcript levels of the ABA conjugating HvBG7 enzyme were elevated in the HvNAC6 RNAi lines, but this effect was not clearly associated with transgene-mediated resistance. Together, these data support a function of HvNAC6 as a regulator of ABA-mediated defence responses for maintenance of effective basal resistance against Bgh.
authors.affiliation: Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Denmark.
authors.forename: Yan-Jun
authors.initials: YJ
authors.lastname: Chen
authors.forename: Venura
authors.initials: V
authors.lastname: Perera
authors.forename: Michael W
authors.initials: MW
authors.lastname: Christiansen
authors.forename: Inger B
authors.initials: IB
authors.lastname: Holme
authors.forename: Per L
authors.initials: PL
authors.lastname: Gregersen
authors.forename: Murray R
authors.initials: MR
authors.lastname: Grant
authors.forename: David B
authors.initials: DB
authors.lastname: Collinge
authors.forename: Michael F
authors.initials: MF
authors.lastname: Lyngkjær
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism / Q000502:physiology*; D001203:Ascomycota / Q000472:pathogenicity*; D060467:Disease Resistance / Q000235:genetics / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D055785:Gene Knockdown Techniques; D017343:Genes, Plant / Q000502:physiology; D001467:Hordeum / Q000235:genetics / Q000502:physiology*; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology / Q000382:microbiology*; D010937:Plant Growth Regulators / Q000378:metabolism / Q000502:physiology*; D016133:Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
chemical_list: D010937:Plant Growth Regulators; D014157:Transcription Factors; D000040:Abscisic Acid
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