Expression of gynoecium patterning transcription factors in (Aristolochiaceae) and their contribution to gynostemium development.

BACKGROUND

In (Aristolochiaceae) flowers, the congenital fusion of the anthers and the commissural, stigmatic lobes forms a gynostemium. Although the molecular bases associated to the apical-basal gynoecium patterning have been described in eudicots, comparative expression studies of the style and stigma regulatory genes have never been performed in early divergent angiosperms possessing a gynostemium.

RESULTS

In this study, we assess the expression of five genes typically involved in gynoecium development in . We found that all five genes (, , , and ) are expressed in the ovary, the placenta, the ovules and the transmitting tract. In addition, only , and are temporarily expressed during the initiation of the stigma, while none of the genes studied is maintained during the elaboration of the stigmatic surfaces in the gynostemium.

CONCLUSIONS

Expression patterns suggest that , , and homologs establish ovary and style identity in Only , and genes may play a role in the early differentiation of the stigmatic lobes, but none of the genes studied seems to control late stigma differentiation in the gynostemium. The data gathered so far raises the possibility that such transient expression early on provides sufficient signal for late stigma differentiation or that unidentified late identity genes are controlling stigma development in the gynostemium. Our data does not rule out the possibility that stigmas could correspond to staminal filaments with convergent pollen-receptive surfaces.