Auxin-induced K+ channel expression represents an essential step in coleoptile growth and gravitropism.
Auxin-induced growth of coleoptiles depends on the presence of potassium and is suppressed by K+ channel blockers. To evaluate the role of K+ channels in auxin-mediated growth, we isolated and functionally expressed ZMK1 and ZMK2 (Zea mays K+ channel 1 and 2), two potassium channels from maize coleoptiles. In growth experiments, the time course of auxin-induced expression of ZMK1 coincided with the kinetics of coleoptile elongation. Upon gravistimulation of maize seedlings, ZMK1 expression followed the gravitropic-induced auxin redistribution. K+ channel expression increased even before a bending of the coleoptile was observed. The transcript level of ZMK2, expressed in vascular tissue, was not affected by auxin. In patch-clamp studies on coleoptile protoplasts, auxin increased K+ channel density while leaving channel properties unaffected. Thus, we conclude that coleoptile growth depends on the transcriptional up-regulation of ZMK1, an inwardly rectifying K+ channel expressed in the nonvascular tissue of this organ.
Philippar
K
K
Julius-von-Sachs-Institut, Lehrstuhl Molekulare Pflanzenphysiologie und Biophysik, Wurzburg, Germany.
Fuchs
I
I
Luthen
H
H
Hoth
S
S
Bauer
C S
CS
Haga
K
K
Thiel
G
G
Ljung
K
K
Sandberg
G
G
Bottger
M
M
Becker
D
D
Hedrich
R
R
D000818:Animals; D018548:Cotyledon / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D018522:Gravitropism / Q000502:physiology*; D007210:Indoleacetic Acids / Q000378:metabolism* / Q000494:pharmacology; D009280:Naphthaleneacetic Acids / Q000378:metabolism / Q000494:pharmacology; D009865:Oocytes; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology; D018520:Plant Shoots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D014981:Xenopus; D003313:Zea mays / Q000235:genetics / Q000254:growth & development
D007210:Indoleacetic Acids; D009280:Naphthaleneacetic Acids; D010937:Plant Growth Regulators; D015221:Potassium Channels; C034182:1-naphthaleneacetic acid; C030737:indoleacetic acid