title: Outward-rectifying K+ channel activities regulate cell elongation and cell division of tobacco BY-2 cells.
abstract: Potassium ions (K+) are required for plant growth and development, including cell division and cell elongation/expansion, which are mediated by the K+ transport system. In this study, we investigated the role of K+ in cell division using tobacco BY-2 protoplast cultures. Gene expression analysis revealed induction of the Shaker-like outward K+ channel gene, NTORK1, under cell-division conditions, whereas the inward K+ channel genes NKT1 and NtKC1 were induced under both cell-elongation and cell-division conditions. Repression of NTORK1 gene expression by expression of its antisense construct repressed cell division but accelerated cell elongation even under conditions promoting cell division. A decrease in the K+ content of cells and cellular osmotic pressure in dividing cells suggested that an increase in cell osmotic pressure by K+ uptake is not required for cell division. In contrast, K+ depletion, which reduced cell-division activity, decreased cytoplasmic pH as monitored using a fluorescent pH indicator, SNARF-1. Application of K+ or the cytoplasmic alkalizing reagent (NH(4))(2)SO(4) increased cytoplasmic pH and suppressed the reduction in cell-division activity. These results suggest that the K+ taken up into cells is used to regulate cytoplasmic pH during cell division.
authors.affiliation: Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Sano
authors.forename: Natsumaro
authors.initials: N
authors.lastname: Kutsuna
authors.forename: Dirk
authors.initials: D
authors.lastname: Becker
authors.forename: Rainer
authors.initials: R
authors.lastname: Hedrich
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Hasezawa
mesh_terms: D002455:Cell Division; D049108:Cell Enlargement; D002478:Cells, Cultured; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D009997:Osmotic Pressure; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D011523:Protoplasts / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D051637:Shaker Superfamily of Potassium Channels / Q000235:genetics / Q000378:metabolism*; D014026:Nicotiana / Q000166:cytology* / Q000235:genetics / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D018749:RNA, Plant; D051637:Shaker Superfamily of Potassium Channels; D011188:Potassium