Interaction between the GROWTH-REGULATING FACTOR and KNOTTED1-LIKE HOMEOBOX families of transcription factors

Plant Physiol. 2014 Apr;164(4):1952-66. doi: 10.1104/pp.113.222836. Epub 2014 Feb 14.

Abstract

KNOTTED1-LIKE HOMEOBOX (KNOX) genes are important regulators of meristem function, and a complex network of transcription factors ensures tight control of their expression. Here, we show that members of the GROWTH-REGULATING FACTOR (GRF) family act as players in this network. A yeast (Saccharomyces cerevisiae) one-hybrid screen with the upstream sequence of the KNOX gene Oskn2 from rice (Oryza sativa) resulted in isolation of OsGRF3 and OsGRF10. Specific binding to a region in the untranslated leader sequence of Oskn2 was confirmed by yeast and in vitro binding assays. ProOskn2:β-glucuronidase reporter expression was down-regulated by OsGRF3 and OsGRF10 in vivo, suggesting that these proteins function as transcriptional repressors. Likewise, we found that the GRF protein BGRF1 from barley (Hordeum vulgare) could act as a repressor on an intron sequence in the KNOX gene Hooded/Barley Knotted3 (Bkn3) and that AtGRF4, AtGRF5, and AtGRF6 from Arabidopsis (Arabidopsis thaliana) could repress KNOTTED-LIKE FROM ARABIDOPSIS THALIANA2 (KNAT2) promoter activity. OsGRF overexpression phenotypes in rice were consistent with aberrant meristematic activity, showing reduced formation of tillers and internodes and extensive adventitious root/shoot formation on nodes. These effects were associated with down-regulation of endogenous Oskn2 expression by OsGRF3. Conversely, RNA interference silencing of OsGRF3, OsGRF4, and OsGRF5 resulted in dwarfism, delayed growth and inflorescence formation, and up-regulation of Oskn2. These data demonstrate conserved interactions between the GRF and KNOX families of transcription factors in both monocot and dicot plants.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / metabolism*
  • DNA, Plant / metabolism
  • Down-Regulation / genetics
  • Gene Expression Regulation, Plant
  • Gene Silencing
  • Glucuronidase / metabolism
  • Hordeum / metabolism*
  • Organ Specificity / genetics
  • Oryza / genetics
  • Oryza / metabolism*
  • Oryza / ultrastructure
  • Phenotype
  • Plant Leaves / metabolism
  • Plant Leaves / ultrastructure
  • Plant Proteins / chemistry
  • Plant Proteins / metabolism*
  • Plant Roots / growth & development
  • Plant Shoots / growth & development
  • Promoter Regions, Genetic / genetics
  • Protein Binding
  • Protein Structure, Tertiary
  • Saccharomyces cerevisiae / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Two-Hybrid System Techniques
  • Up-Regulation

Substances

  • DNA, Plant
  • Plant Proteins
  • Transcription Factors
  • Glucuronidase