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DEVELOPMENT AND HORMONE ACTION

Arabidopsis Genes AS1, AS2, and JAG Negatively Regulate Boundary-Specifying Genes to Promote Sepal and Petal Development^1,[W]

National Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (B.X., H.W., H.H.); State Key Laboratory of Genetic Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200433, China (Z.L., Y.Z., A.D.); and Department of Biology and the Huck Institute for the Life Sciences, Pennsylvania State University, University Park, Pennsylvania 16802 (H.M.)

Boundary formation is crucial for organ development in multicellular eukaryotes. In higher plants, boundaries that separate the organ primordia from their surroundings have relatively low rates of cell proliferation. This cellular feature is regulated by the actions of certain boundary-specifying genes, whose ectopic expression in organs can cause inhibition of organ growth. Here, we show that the Arabidopsis thaliana ASYMMETRIC LEAVES1 and 2 (AS1 and AS2) and JAGGED (JAG) genes function in the sepal and petal primordia to repress boundary-specifying genes for normal development of the organs. Loss-of-function as1 jag and as2 jag double mutants produced extremely tiny sepals and petals. Analysis of a cell-cycle marker HISTONE4 revealed that cell division in sepal primordia of the double mutant was inhibited. Moreover, these abnormal sepals and petals exhibited ectopic overexpression of the boundary-specifying genes PETAL LOSS (PTL) and CUP-SHAPED COTYLEDONS1 and 2 (CUC1 and CUC2). Loss of PTL or CUC1 and CUC2 functions in the as1 jag background could partially rescue the tiny sepal and petal phenotypes, supporting the model that the tiny sepal/petal phenotypes are caused, at least in part, by ectopic expression of boundary-specifying genes. Together, our data reveal a previously unrecognized fundamental regulation by which AS1, AS2, and JAG act to define sepal and petal from their boundaries.

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: Hai Huang (hhuang{at}sippe.ac.cn).

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

www.plantphysiol.org/cgi/doi/10.1104/pp.107.113787

^* Corresponding author; e-mail hhuang{at}sippe.ac.cn.

Received November 23, 2007; accepted December 13, 2007; published December 21, 2007.