SummaryOverexpression of bacterial c-glutamylcysteine synthetase in the cytosol of Populus tremula 9 P. alba produces higher glutathione (GSH) concentrations in leaves, thereby indicating the potential for cadmium (Cd)

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Summary. During Petunia hybrida seed development, the MADSbox genes encoding the floral binding proteins (FBP) 7 and 11 are expressed in the seed coat and not in the endosperm or embryo. These proteins are thought to function as transcription factors and are essential for ovule formation in Petunia spp. Immunocytochemical methods were used to analyze the distribution of FBP7 and FBPll after fertilization in wild type and ectopic and cosuppression mutants. During the first nine days of seed development the protein was found in the nuclei of seed coat cells, of both wild-type plants and plants which ectopically expressed FBPll. The signal for FBP7 and -11 proteins diminished during seed development, was first lost in the outer epidermis of the seed coat, then in the endothelium, and finally, at 9 days after pollination (DAP), the protein could not be detected anymore in the parenchyma ceils of the seed coat. Although the distribution patterns in wild-type and FBPll ectopically expressing plants are similar, the latter exhibited higher protein levels. A mild-cosuppression mutant of FBP7 and FBPll, having only a total of 5% FBP7 and -11 mRNA, showed hardly any FBP7 and -11 proteins.The lack of FBP7 and -11 caused endosperm degeneration in the mutant at a moment when the protein had already decreased to an undetectable level in the wild type and ectopic expression mutant (i.e., at 13 DAP). It is suggested that till about 9 DAP a minimal amount of FBP7 and -11 is needed for the normal functioning of the seed coat during later stages, i.e., for transfer of nutrients to endosperm and embryo. Besides the immunocytochemical data on the FBP7 and FBPll MADS-box gene products, the morphological analysis of wild type and mutants contributes details on early seed development in Petunia hybrida.