Floral Organs of the Same Type but at Different Positions within the Flower of Sinapis alba (Brassicaceae) Display Identical Protein Patterns

Different interpretations of the flower of the Brassicaceae exist, suggesting the presence of either 4, 5 or 6 whorls of floral organs. In these models, the 2 short and 4 long stamens account for either 1or 2 whorls, as do the lateral and median sepals. We have searched for inside-whorl differences in gene expression in the Brassicaceae through 2D-PAGE analysis of the total protein pattern of short and long stamens, as well as lateral and median sepals, in Sinapis alba. No detected polypeptide is specific to one type of stamen, none is specific to one type of sepal. On the other hand, about 10% of the polypeptides are specific of one stage of development when long stamens from 4-mm flower buds are compared with long stamens sampled at anthesis. These results suggest that at the molecular level only 4 whorls are detectable and that subtle quantitative variations may account for inside-whorl differences in morphology.