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DEVELOPMENT AND HORMONE ACTION

The turnip Mutant of Arabidopsis Reveals That LEAFY COTYLEDON1 Expression Mediates the Effects of Auxin and Sugars to Promote Embryonic Cell Identity^1,[W]

Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, Durham DH1 3LE, United Kingdom

The transition from embryonic to vegetative growth marks an important developmental stage in the plant life cycle. The turnip (tnp) mutant was identified in a screen for modifiers of POLARIS expression, a gene required for normal root growth. Mapping and molecular characterization of tnp shows that it represents a gain-of-function mutant of LEAFY COTYLEDON1 (LEC1), due to a promoter mutation. This results in the ectopic expression of LEC1, but not of other LEC genes, in vegetative tissues. The LEC class of genes are known regulators of embryogenesis, involved in the control of embryonic cell identity by currently unknown mechanisms. Activation of the LEC-dependent pathway in tnp leads to the loss of hypocotyl epidermal cell marker expression and loss of SCARECROW expression in the endodermis, the ectopic accumulation of starch and lipids, and the up-regulation of early and late embryonic genes. tnp also shows partial deetiolation during dark growth. Penetrance of the mutant phenotype is strongly enhanced in the presence of exogenous auxin and sugars, but not by gibberellin or abscisic acid, and is antagonized by cytokinin. We propose that the role of LEC1 in embryonic cell fate control requires auxin and sucrose to promote cell division and embryonic differentiation.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Keith Lindsey (keith.lindsey{at}durham.ac.uk).

^[W] The online version of this article contains Web-only data.

www.plantphysiol.org/cgi/doi/10.1104/pp.106.080895

^* Corresponding author; e-mail keith.lindsey{at}durham.ac.uk; fax 44–191–334–1201.

Received March 26, 2006; accepted July 31, 2006; published September 1, 2006.

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