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First published online June 4, 2004; 10.1104/pp.104.038711 Plant Physiology 135:959-968 (2004) © 2004 American Society of Plant Biologists Interaction between Wall Deposition and Cell Elongation in Dark-Grown Hypocotyl Cells in Arabidopsis1Laboratoire de Biologie Cellulaire, Institut National de la Recherche Agronomique, 78026 Versailles Cedex, France (G.R., S.P., H.H.); and Centre Commun de Microscopie Electronique, Correspondant Formation CNRS, UMR 8080, Université Paris XI, 91 405 Orsay Cedex, France (D.J.)
A central problem in plant biology is how cell expansion is coordinated with wall synthesis. We have studied growth and wall deposition in epidermal cells of dark-grown Arabidopsis hypocotyls. Cells elongated in a biphasic pattern, slowly first and rapidly thereafter. The growth acceleration was initiated at the hypocotyl base and propagated acropetally. Using transmission and scanning electron microscopy, we analyzed walls in slowly and rapidly growing cells in 4-d-old dark-grown seedlings. We observed thick walls in slowly growing cells and thin walls in rapidly growing cells, which indicates that the rate of cell wall synthesis was not coupled to the cell elongation rate. The thick walls showed a polylamellated architecture, whereas polysaccharides in thin walls were axially oriented. Interestingly, innermost cellulose microfibrils were transversely oriented in both slowly and rapidly growing cells. This suggested that transversely deposited microfibrils reoriented in deeper layers of the expanding wall. No growth acceleration, only slow growth, was observed in the cellulose synthase mutant cesA6prc1-1 or in seedlings, which had been treated with the cellulose synthesis inhibitor isoxaben. In these seedlings, innermost microfibrils were transversely oriented and not randomized as has been reported for other cellulose-deficient mutants or following treatment with dichlorobenzonitrile. Interestingly, isoxaben treatment after the initiation of the growth acceleration in the hypocotyl did not affect subsequent cell elongation. Together, these results show that rapid cell elongation, which involves extensive remodeling of the cell wall polymer network, depends on normal cellulose deposition during the slow growth phase.
1 This work was supported by the Ministère de la Recherche et Technologie (Ph.D. fellowship to G.R.), the Action Concertée Incitative, Développement et Physiologie intégrative (grant no. 47 to H.H.), and the European Economic Commission Framework 5 Program (GEMINI to H.H.). Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.038711. * Corresponding author; e-mail herman.hofte{at}versailles.inra.fr; fax 33–1–30833099. Received January 6, 2004; returned for revision March 1, 2004; accepted March 1, 2004. This article has been cited by other articles:
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