Temporal and Spatial Expression of MADS Box Genes, FBP7 and FBP11, During Initiation and Early Development of Ovules in Wild Type and Mutant Petunia hybrida

Abstract: The temporal and spatial distribution of the Petunia Floral Binding Proteins 7 and 11 (FBP7/11) were determined immunocytochemically during ovule initiation and development. In wild type plants, FBP7/11 were first detected in the placenta before ovule primordia were formed. At ovule primordium stage, FBP7/11 levels increased in the placenta and appeared in ovule primordia at the sites where integument primordia developed. At the megagametogenesis stage, FBP7/11 were present at high levels in the placenta, funicle and integument, but not in the nucellus or gametophyte. Transgenics with cosuppression of FBP7/11 formed normal ovule primordia on the placenta from which both normal ovules and carpel-like structures developed. The amount of FBP7/11 was low in the ovules and undetectable in the carpel-like structures. Plants with ectopic expression of FBP7/11 developed normal ovules on the placenta and, in addition, ovule- and carpel-like structures on sepals. Placental and sepal ovules showed the same labeling pattern as observed in wild type ovules. FBP7/11 levels were, however, low or undetectable in the carpel-like structures. The results indicate that FBP7/11 only have indirect roles in ovule primordium initiation. However, at least small quantities are needed for proper ovule differentiation. Thus, the amount of FBP7/11 is related to the type of development after primordium formation, i.e., towards the formation of real ovules or carpel-like structures.