Different subcellular localization and trafficking properties of KNOX class 1 homeodomain proteins from rice

Plant Mol Biol. 2004 Aug;55(6):781-96. doi: 10.1007/s11103-004-1967-3.


Genes of the KN1-like homeobox (KNOX) class 1 encode transcription factors involved in shoot apical meristem development and maintenance. We studied the subcellular localization of Green Fluorescent Protein-tagged rice KNOX proteins (Oskn1-3) after particle bombardment of onion and rice cells and after transformation of Arabidopsis and rice with constitutive and inducible expression constructs. In all test systems, the three rice KNOX proteins showed nuclear and cytoplasmic localization patterns. However, Oskn1 additionally showed in some cells a distribution over punctae moving randomly in the cytosol. Use of an inducible expression system indicated a nuclear presence of Oskn1 in cells of the shoot apical meristem and post-transcriptional down-regulation in early leaf primordia. Arabidopsis and rice test systems were used to study effects of plant hormones and auxin transport inhibition on KNOX protein localization. Application of GA3 or 1-NAA shifted protein localization completely to the cytoplasm and resulted in loss of the punctae formed by Oskn1. Conversely, NPA application induced a complete nuclear localization of the KNOX proteins. To study intercellular movement of the KNOX proteins we set up a novel co-bombardment assay in which trafficking of untagged KNOX proteins was visualized through the co-trafficking of green fluorescent or blue fluorescent marker proteins. In multiple independent experiments Oskn1 trafficked more extensively to neighboring cells than Oskn2 and Oskn3. Differences in the localization and trafficking properties of Oskn1, Oskn2 and Oskn3 correlate with differences in mRNA localization patterns and functional differences between the rice KNOX genes and their putative orthologues from other species.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 2,4-Dichlorophenoxyacetic Acid / pharmacology
  • Amino Acid Sequence
  • Arabidopsis / genetics
  • Arabidopsis / metabolism
  • Benzyl Compounds / pharmacology
  • Gibberellins / pharmacology
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Homeodomain Proteins / genetics
  • Homeodomain Proteins / metabolism*
  • Molecular Sequence Data
  • Naphthaleneacetic Acids / pharmacology
  • Onions / cytology
  • Onions / genetics
  • Onions / metabolism
  • Oryza / genetics
  • Oryza / metabolism*
  • Plant Epidermis / cytology
  • Plant Epidermis / genetics
  • Plant Epidermis / metabolism
  • Plant Growth Regulators / pharmacology
  • Plant Leaves / cytology
  • Plant Leaves / genetics
  • Plant Leaves / metabolism
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*
  • Plants, Genetically Modified
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Protein Transport / drug effects
  • Purines / pharmacology
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Transfection


  • Benzyl Compounds
  • Gibberellins
  • Homeodomain Proteins
  • Knox1 protein, plant
  • Naphthaleneacetic Acids
  • Plant Growth Regulators
  • Plant Proteins
  • Protein Isoforms
  • Purines
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • 2,4-Dichlorophenoxyacetic Acid
  • 1-naphthaleneacetic acid
  • benzylaminopurine