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First published online June 4, 2004; 10.1104/pp.104.040022 Plant Physiology 135:1050-1058 (2004) © 2004 American Society of Plant Biologists Cell Cycle Modulation in the Response of the Primary Root of Arabidopsis to Salt Stress1Department of Plant Systems Biology, University of Ghent/Vlaams Interuniversitair Instituut voor Biotechnologie (VIB), 9052 Ghent, Belgium
Salt stress inhibits plant growth and development. We investigated the importance of cell cycle regulation in mediating the primary root growth response of Arabidopsis to salt stress. When seedlings were transferred to media with increasing concentrations of NaCl, root growth rate was progressively reduced. At day 3 after transfer of seedlings to growth medium containing 0.5% NaCl the primary roots grew at a constant rate well below that prior to the transfer, whereas those transferred to control medium kept accelerating. Kinematic analysis revealed that the growth reduction of the stressed roots was due to a decrease in cell production and a smaller mature cell length. Surprisingly, average cell cycle duration was not affected. Hence, the reduced cell production was due to a smaller number of dividing cells, i.e. a meristem size reduction. To analyze the mechanism of meristem size adaptation prior to day 3, we investigated the short-term cell cycle events following transfer to saline medium. Directly after transfer cyclin-dependent kinase (CDK) activity and CYCB1;2 promoter activity were transiently reduced. Because protein levels of both CDKA;1 and CDKB1;1 were not affected, the temporary inhibition of mitotic activity that allows adaptation to the stress condition is most likely mediated by posttranslational control of CDK activity. Thus, the adaptation to salt stress involves two phases: first, a rapid transient inhibition of the cell cycle that results in fewer cells remaining in the meristem. When the meristem reaches the appropriate size for the given conditions, cell cycle duration returns to its default.
1 This work was supported by the Instituut voor de aanmoediging van Innovatie door Wetenschap en Technologie in Vlaanderen (predoctoral fellowship to G.W.), by grants from the Interuniversity Poles of Attraction Programme (Belgian State, Prime Minister's Office-Federal Office for Scientific, Technical and Cultural Affairs; P5/13), and by the European Commission Quality of Life and Management of Living Resources program (QLK5–CT–2001–01871). Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.040022. * Corresponding author; e-mail dirk.inze{at}psb.ugent.be; fax 32–9–331–39–09. Received January 30, 2004; returned for revision April 8, 2004; accepted April 10, 2004. This article has been cited by other articles:
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