Plant and Cell Physiology Advance Access originally published online on January 6, 2007
Plant and Cell Physiology 2007 48(2):278-286; doi:10.1093/pcp/pcm002
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Dissection of Enhanced Cell Expansion Processes in Leaves Triggered by a Defect in Cell Proliferation, with Reference to Roles of Endoreduplication
1National Institute for Basic Biology, Myodaiji-cho Nisigo Naka 38, Okazaki, Aichi, 444-8585 Japan
2Graduate University for Advanced Studies, Hayama, Kanagawa, 240-1930 Japan
3Graduate School of Science, University of Tokyo, Science Building #2, 7-3-1 Hongo, Tokyo 113-0033 Japan
*Corresponding author: E-mail, ghori{at}nibb.ac.jp; Fax, +81-564-55-7512.
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Abstract |
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Leaf development relies on cell proliferation, post-mitotic cell expansion and the coordination of these processes. In several Arabidopsis thaliana mutants impaired in cell proliferation, such as angustifolia3 (an3), leaf cells are larger than normal at their maturity. This phenomenon, which we call compensated cell enlargement, suggests the presence of such coordination in leaf development. To dissect genetically the cell expansion system(s) underlying this compensation seen in the an3 mutant, we isolated and utilized 10 extra-small sisters (xs) mutant lines that show decreased cell size but normal cell numbers in leaves. In the xs single mutants, the palisade cell sizes in mature leaves are about 20–50% smaller than those of wild-type cells. Phenotypes of the palisade cell sizes in all combinations of xs an3 double mutants fall into three classes. In the first class, the compensated cell enlargement was significantly suppressed. Conversely, in the second class, the defective cell expansion conferred by the xs mutations was significantly suppressed by the an3 mutation. The residual xs mutations had effects additive to those of the an3 mutation on cell expansion. The endopolyploidy levels in the first class of mutants were decreased, unaffected or increased, as compared with those in wild-type, suggesting that the abnormally enhanced cell expansion observed in an3 could be mediated, at least in part, by ploidy-independent mechanisms. Altogether, these results clearly showed that a defect in cell proliferation in leaf primordia enhances a part of the network that regulates cell expansion, which is required for normal leaf expansion.
Keywords: Angustifolia3 - Cell expansion - Compensated cell enlargement - Extra-small sisters - Leaf - Ploidy
Abbreviations: an3, angustifolia3; rhl1, root hairless1; xs, extra-small sisters
4 Present address: Graduate School of Science, University of Tokyo, Science Building #7, 7-3-1 Hongo, Tokyo, 113-0033 Japan.
(Received November 16, 2006; Accepted December 21, 2006)
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