Journal
PLANT JOURNAL
Volume 57, Issue 1, Pages 55-64Publisher
WILEY
DOI: 10.1111/j.1365-313X.2008.03672.x
Keywords
cell division; cell elongation; cell osmotic pressure; cytoplasmic pH; tobacco BY-2; K+ channel
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Funding
- Ministry of Education, Culture, Sports, Science and Technology [19039008, 20061008]
- Institute for Bioinformatics Research and Development (BIRD) of the Japan Science and Technology Agency
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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 (NH4)(2)SO4 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.
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