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DEVELOPMENT AND HORMONE ACTION

The SPOROCYTELESS/NOZZLE Gene Is Involved in Controlling Stamen Identity in Arabidopsis^1,[W],[OA]

Department of Biological Sciences, University of Wisconsin, Milwaukee, Wisconsin 53211 (X.L., J.H., B.S., M.A., A.R., G.J., H.A.O., D.Z.); and Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604 (S.P., T.I.)

The stamen, which consists of an anther and a filament, is the male reproductive organ in a flower. The specification of stamen identity in Arabidopsis (Arabidopsis thaliana) is controlled by a combination of the B genes APETALA3 (AP3) and PISTILLATA, the C gene AGAMOUS (AG), and the E genes SEPALLATA1 (SEP1) to SEP4. The "floral organ-building" gene SPOROCYTELESS/NOZZLE (SPL/NZZ) plays a central role in regulating anther cell differentiation. However, much less is known about how "floral organ identity" and floral organ-building genes interact to control floral organ development. In this study, we report that ectopic expression of SPL/NZZ not only affects flower development in the wild-type background but also leads to the transformation of petal-like organs into stamen-like organs in flowers of ap2-1, a weak ap2 mutant allele. Moreover, our loss-of-function analysis indicates that the spl/nzz mutant enhances the phenotype of the ag weak allele ag-4. Furthermore, ectopic expression and overexpression of SPL/NZZ altered expression of AG, SEP3, and AP2 in rosette leaves and flowers, while ectopic expression of SPL/NZZ resulted in ectopic expression of AG and SEP3 in the outer whorls of flowers. Our results indicate that the SPL/NZZ gene is engaged in controlling stamen identity via interacting with genes required for stamen identity in Arabidopsis.

² Present address: Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.

³ Present address: Department of Genetics, University of Wisconsin, Madison, WI 53706–1574.

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: Dazhong Zhao (dzhao{at}uwm.edu).

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

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.109.145896

^* Corresponding author; e-mail dzhao{at}uwm.edu.

Received August 6, 2009; accepted August 28, 2009; published September 2, 2009.