Floral MADS box genes and homeotic gender dimorphism in Thalictrum dioicum (Ranunculaceae) – a new model for the study of dioecy

doi:10.1111/j.1365-313X.2005.02336.x

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Wiley InterScience

The Plant Journal

Volume 41 Issue 5, Pages 755 - 766

Published Online: 17 Jan 2005

Published in association with the Society for Experimental Biology

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Floral MADS box genes and homeotic gender dimorphism in Thalictrum dioicum (Ranunculaceae) – a new model for the study of dioecy

Verónica S. Di Stilio ¹*^†, Elena M. Kramer ¹ and David A. Baum ^1,2

¹ Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA , and
² Department of Botany, University of Wisconsin, Madison, WI 53706, USA

^* For correspondence (fax +206 616 2011; e-mail distilio@u.washington.edu).

^† Present address: Department of Biology, University of Washington, Seattle, WA 98195, USA.

KEYWORDS

dioecy • homeosis • MADS box genes • APETALA3 • PISTILLATA • AGAMOUS

ABSTRACT

In most dioecious angiosperm species, flowers are initially perfect but abort either stamens or carpels during their development, indicating that sex determination occurs after floral organ identity has been established. Dioecious members of the genus Thalictrum (meadow-rue), however, produce flowers that lack aborted organs. Examination of early flower development of T. dioicum confirms that flowers are male or female from inception, raising the possibility that genetic mechanisms working at or above the level of organ identity promote sex determination through a homeotic-like mechanism. In order to investigate this possibility, we identified homologs of the organ identity genes PISTILLATA (PI), APETALA3 (AP3) and AGAMOUS (AG) from T. dioicum and the hermaphroditic species T. thalictroides. A combination of early and late duplication events was uncovered in these gene lineages and expression analyses indicate that these events are generally associated with divergence in gene regulation. In light of these findings, we discuss the potential of T. dioicum as a new model for the study of sex determination in the basal eudicots.