title: Plant cells must pass a K+ threshold to re-enter the cell cycle.
abstract: Potassium is an inevitable component of plant life, and potassium channels play a pivotal role in plant growth and development. The role of potassium and of K(+) channels in plant cell division and cell-cycle progression, however, has not been determined so far. K(+) channel blocker studies with synchronized tobacco BY-2 cells revealed that K(+) uptake is required for proper cell-cycle progression during the transition from G(1) to S phase. Electrophysiological studies (patch-clamp and voltage-clamp techniques) showed a cell-cycle dependency of K(+) channel activities and reduced driving force for K(+) uptake in dividing cells. Among the four Shaker-like K(+) channel genes expressed in BY-2 cells, NKT1 represents an inwardly rectifying K(+) channel that mediates K(+) uptake. NKT1 is transcriptionally induced during G(1) phase, while transcripts of the outward-rectifier NTORK1 dominate S phase. Elongating BY-2 cells appeared hyperpolarized (-101 +/- 11 mV), and had elevated osmotic pressure and approximately twice the turgor pressure when compared with depolarized (-64 +/- 8 mV) dividing cells. This indicates that cells have to gain a threshold K(+) level to re-enter the cell cycle. Based on these findings, turgor regulation through modulation of K(+) channel density in plant cell division and cell-cycle progression is discussed.
authors.affiliation: Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute, University of Würzburg, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany.
authors.forename: Toshio
authors.initials: T
authors.lastname: Sano
authors.forename: Dirk
authors.initials: D
authors.lastname: Becker
authors.forename: Natalya
authors.initials: N
authors.lastname: Ivashikina
authors.forename: Lars H
authors.initials: LH
authors.lastname: Wegner
authors.forename: Ulrich
authors.initials: U
authors.lastname: Zimmermann
authors.forename: M Rob G
authors.initials: MR
authors.lastname: Roelfsema
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Nagata
authors.forename: Rainer
authors.initials: R
authors.lastname: Hedrich
mesh_terms: D002453:Cell Cycle / Q000502:physiology*; D002478:Cells, Cultured; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000166:cytology* / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011188:Potassium