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

The temporal and spatial distribution of the Petunia Floral Binding Protein s 7 and 11 (FBP7/11) were determined immunocytochemically during ovule init iation 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 in tegument, but not in the nucellus or gametophyte. Transgenics with cosuppre ssion of FBP7/11 formed normal ovule primordia on the placenta from which b oth normal ovules and carpel-like structures developed. The amount of FBP7/ 11 was low in the ovules and undetectable in the carpel-like structures. Pl ants with ectopic expression of FBP7/11 developed normal ovules on the plac enta and, in addition, ovule- and carpel-like structures on sepals. Placent al and sepal ovules showed the same labeling pattern as observed in wild ty pe 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 nee ded for proper ovule differentiation. Thus, the amount of FBP7/11 is relate d to the type of development after primordium formation, i.e., towards the formation of real ovules or carpel-like structures.