Plant Molecular Biology

, Volume 61, Issue 4–5, pp 757–768 | Cite as

The auxin-induced K+ channel gene Zmk1 in maize functions in coleoptile growth and is required for embryo development

  • Katrin Philippar
  • Kai Büchsenschütz
  • David Edwards
  • Julia Löffler
  • Hartwig Lüthen
  • Erhard Kranz
  • Keith J. Edwards
  • Rainer HedrichEmail author


The transcript level and in turn protein density of the K+-uptake channel ZMK1 in maize (Zea mays) coleoptiles is controlled by the phytohormone auxin. ZMK1 is involved in auxin-regulated coleoptile elongation as well as gravi- and phototropism. To provide unequivocal evidence for the role of ZMK1 in these elementary processes we screened for maize plants containing a Mutator-tagged Zmk1 gene. In a site-selected approach, we were able to identify three independent alleles of Mutator-transposon insertions in Zmk1. zmk1-m1::Mu1 plants were characterised by a Mu1 transposon inside intron 1 of ZMK1. When we analysed the Zmk1-transcript abundance in growing coleoptiles of these homozygous mutants, however, we found the K+-channel allele overexpressed. In consequence, elevated levels of K+-channel transcripts resulted in a growth phenotype as expected from more efficient K+-uptake, representing a central factor for turgor formation. Following Zmk1 expression during maize embryogenesis, we found this K+-channel gene constitutively expressed throughout embryo development and upregulated in late stages. In line with a vital role in embryogenesis, the mutations of exon 2 and intron 2 of Zmk1-zmk1-m2::Mu8 and zmk1-m3::MuA2-caused a lethal, defective-kernel phenotype. Thus, these results demonstrate the central role of the auxin-regulated K+-channel gene Zmk1 in coleoptile growth and embryo development.


Auxin Coleoptile growth Embryo development K+ channel Maize Mutator transposons 



Zea mays K+ channel 1




indole-3-acetic acid




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Copyright information

© Springer Science+Business Media B.V. 2006

Authors and Affiliations

  • Katrin Philippar
    • 1
    • 5
  • Kai Büchsenschütz
    • 1
  • David Edwards
    • 2
  • Julia Löffler
    • 3
  • Hartwig Lüthen
    • 3
  • Erhard Kranz
    • 3
  • Keith J. Edwards
    • 4
  • Rainer Hedrich
    • 1
    Email author
  1. 1.Julius-von-Sachs-Institut, Lehrstuhl Molekulare Pflanzenphysiologie und BiophysikUniversität WürzburgWuerzburgGermany
  2. 2.Primary Industries Research Victoria, Department of Primary IndustriesLa Trobe UniversityBundooraAustralia
  3. 3.Biozentrum Klein Flottbek und Botanischer GartenUniversität HamburgHamburgGermany
  4. 4.School of Biological SciencesUniversity of BristolBristolUK
  5. 5.Department für Biologie 1, Botanik IIILudwig-Maximilians-Universität MünchenMunichGermany

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