JXB Advance Access published online on September 18, 2009
Journal of Experimental Botany, doi:10.1093/jxb/erp279
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© 2009 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.5/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)
RESEARCH PAPER |
Functional characterization of B class MADS-box transcription factors in Gerbera hybrida



Department of Applied Biology, PO Box 27, University of Helsinki, FIN-00014 Finland
To whom correspondence should be addressed. E-mail: teemu.teeri{at}helsinki.fi
According to the classical ABC model, B-function genes are involved in determining petal and stamen development. Most core eudicot species have B class genes belonging to three different lineages: the PI, euAP3, and TM6 lineages, although both Arabidopsis and Antirrhinum appear to have lost their TM6-like gene. Functional studies were performed for three gerbera (Gerbera hybrida) B class MADS-box genes—PI/GLO-like GGLO1, euAP3 class GDEF2, and TM6-like GDEF1—and data are shown for a second euAP3-like gene, GDEF3. In phylogenetic analysis, GDEF3 is a closely related paralogue of GDEF2, and apparently stems from a duplication common to all Asteraceae. Expression analysis and transgenic phenotypes confirm that GGLO1 and GDEF2 mediate the classical B-function since they determine petal and stamen identities. However, based on assays in yeast, three B class heterodimer combinations are possible in gerbera. In addition to the interaction of GGLO1 and GDEF2 proteins, GGLO1 also pairs with GDEF1 and GDEF3. This analysis of GDEF1 represents the first functional characterization of a TM6-like gene in a core eudicot species outside Solanaceae. Similarly to its relatives in petunia and tomato, the expression pattern and transgenic phenotypes indicate that GDEF1 is not involved in determination of petal identity, but has a redundant role in regulating stamen development.
Key words: Asteraceae, evo–devo, flower development, organ identity
* Present address: Department of Health Sciences, PO Box 35, University of Jyväskylä, FIN-40014, Finland.
Present address: Department of Biological and Environmental Sciences, PO Box 56, University of Helsinki, Finland.
Present address: Department of Biological Sciences, University at Buffalo (SUNY), Buffalo, NY 14260, USA.
Received 26 June 2009; Revised 21 August 2009 Accepted 24 August 2009