title: Drought-Up-Regulated TaNAC69-1 is a Transcriptional Repressor of TaSHY2 and TaIAA7, and Enhances Root Length and Biomass in Wheat.
abstract: A well-known physiological adaptation process of plants encountering drying soil is to achieve water balance by reducing shoot growth and maintaining or promoting root elongation, but little is known about the molecular basis of this process. This study investigated the role of a drought-up-regulated Triticum aestivum NAC69-1 (TaNAC69-1) in the modulation of root growth in wheat. TaNAC69-1 was predominantly expressed in wheat roots at the early vegetative stage. Overexpression of TaNAC69-1 in wheat roots using OsRSP3 (essentially root-specific) and OsPIP2;3 (root-predominant) promoters resulted in enhanced primary seminal root length and a marked increase in maturity root biomass. Competitive growth analysis under water-limited conditions showed that OsRSP3 promoter-driven TaNAC69-1 transgenic lines produced 32% and 35% more above-ground biomass and grains than wild-type plants, respectively. TaNAC69-1 overexpression in the roots down-regulated the expression of TaSHY2 and TaIAA7, which are from the auxin/IAA (Aux/IAA) transcriptional repressor gene family and are the homologs of negative root growth regulators SHY2/IAA3 and IAA7 in Arabidopsis. The expression of TaSHY2 and TaIAA7 in roots was down-regulated by drought stress and up-regulated by cytokinin treatment, which inhibited root growth. DNA binding and transient expression analyses revealed that TaNAC69-1 bound to the promoters of TaSHY2 and TaIAA7, acted as a transcriptional repressor and repressed the expression of reporter genes driven by the TaSHY2 or TaIAA7 promoter. These data suggest that TaNAC69-1 is a transcriptional repressor of TaSHY2 and TaIAA7 homologous to Arabidopsis negative root growth regulators and is likely to be involved in promoting root elongation in drying soil.
authors.affiliation: College of Agronomy, Northwest Agriculture and Forestry University, Yangling, Shaanxi 712100, PR China.|CSIRO Agriculture, 306 Carmody Rd., St Lucia, Qld 4067, Australia.
authors.forename: Dandan
authors.initials: D
authors.lastname: Chen
authors.affiliation: CSIRO Agriculture, Clunies Ross Street, Canberra, ACT 2601, Australia.
authors.forename: Terese
authors.initials: T
authors.lastname: Richardson
authors.affiliation: College of Agronomy, Northwest Agriculture and Forestry University, Yangling, Shaanxi 712100, PR China gang-ping.xue@csiro.au chaishoucheng@126.com.
authors.forename: Shoucheng
authors.initials: S
authors.lastname: Chai
authors.affiliation: CSIRO Agriculture, 306 Carmody Rd., St Lucia, Qld 4067, Australia.
authors.forename: C
authors.initials: C
authors.lastname: Lynne McIntyre
authors.affiliation: CSIRO Agriculture, 306 Carmody Rd., St Lucia, Qld 4067, Australia.
authors.forename: Anne L
authors.initials: AL
authors.lastname: Rae
authors.affiliation: CSIRO Agriculture, 306 Carmody Rd., St Lucia, Qld 4067, Australia gang-ping.xue@csiro.au chaishoucheng@126.com.
authors.forename: Gang-Ping
authors.initials: GP
authors.lastname: Xue
mesh_terms: D018533:Biomass; D019921:Biotinylation; D002467:Cell Nucleus / Q000378:metabolism; D003583:Cytokinins / Q000494:pharmacology; D018744:DNA, Plant / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics; D055864:Droughts; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000033:anatomy & histology* / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D012097:Repressor Proteins / Q000378:metabolism; D013312:Stress, Physiological / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D014908:Triticum / Q000033:anatomy & histology / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics*
chemical_list: D003583:Cytokinins; D018744:DNA, Plant; D010940:Plant Proteins; D012097:Repressor Proteins; D049452:Green Fluorescent Proteins
keywords: 
  Triticum aestivum
  ; Drought stress; NAC transcription factor; Root elongation; Root expression; Transcriptional repressor