Molecular characterization of His-Asp phosphorelay signaling factors in maize leaves: implications of the signal divergence by cytokinin-inducible response regulators in the cytosol and the nuclei

Plant Mol Biol. 2003 May;52(2):331-41. doi: 10.1023/a:1023971315108.


Genes for histidyl-aspartyl (His-Asp) phosphorelay components (His-containing phosphotransfer proteins, HP, and response regulators, RR) were isolated from Zea mays L. to characterize their function in cytokinin signaling. Six type-A RRs (ZmRR1, ZmRR2, ZmRR4-ZmRR7), 3 type-B RRs (ZmRR8-ZmRR10), and 3 HPs (ZmHP1-ZmHP3) were found in leaves. All type-A RR genes expressed in leaves were up-regulated by exogenous cytokinin. Transient expression of fusion products of the signaling modules with green fluorescent protein in epidermal leaf cells suggested cytosolic and nuclear localizations of ZmHPs, whereas type-B ZmRR8 was restricted to the nucleus. Type-A RRs were localized partly to the cytosol (ZmRR1, ZmRR2, and ZmRR3) and partly to the nucleus (ZmRR4, ZmRR5, and ZmRR6). In the yeast two-hybrid assay, ZmHP1 and ZmHP3 interacted with both cytosolic ZmRR1 and nuclear type-B ZmRRs. In vitro experiments demonstrated that ZmHPs function as a phospho-donor for ZmRRs; turnover rates of the phosphorylated state were tenfold lower in ZmRR8 and ZmRR9 than in ZmRR1 and ZmRR4. These results suggest that the His-Asp phosphorelay signaling pathway might diverge into a cytosolic and a nuclear branch in leaves of maize, and that the biochemical nature of ZmRRs is different in terms of stability of the phosphorylated status.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aspartic Acid / metabolism*
  • Cell Nucleus / genetics
  • Cloning, Molecular
  • Cytokinins / pharmacology
  • Cytosol / metabolism
  • DNA, Complementary / chemistry
  • DNA, Complementary / genetics
  • Gene Expression Regulation, Plant / drug effects
  • Genetic Variation
  • Green Fluorescent Proteins
  • Histidine / metabolism*
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Microscopy, Confocal
  • Molecular Sequence Data
  • Phosphorylation
  • Phylogeny
  • Plant Leaves / genetics*
  • Plant Proteins / genetics
  • Plant Proteins / metabolism
  • Protein Binding
  • RNA, Plant / drug effects
  • RNA, Plant / genetics
  • RNA, Plant / metabolism
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Saccharomyces cerevisiae / genetics
  • Sequence Analysis, DNA
  • Signal Transduction / drug effects
  • Signal Transduction / genetics*
  • Two-Hybrid System Techniques
  • Zea mays / genetics*


  • Cytokinins
  • DNA, Complementary
  • Luminescent Proteins
  • Plant Proteins
  • RNA, Plant
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • Aspartic Acid
  • Histidine

Associated data

  • GENBANK/AB060130
  • GENBANK/AB062095
  • GENBANK/AB071695
  • GENBANK/AB089191