Downregulation of ovule-specific MADS box genes from petunia results in maternally controlled defects in seed development.

A maternally determined seed defect has been obtained by downregulation of the petunia MADS box genes Floral Binding Protein 7 (FBP7) and FBP11. These genes have been previously shown to play central roles in the determination of ovule identity. Aberrant development of the seed coat and consequent degeneration of the endosperm have been observed in transgenic plants in which these two genes are downregulated by cosuppression. Analysis of the expression pattern of FBP7 and FBP11 and genetic analysis confirmed the maternal inheritance of the phenotype. The FBP7 promoter was cloned and fused to reporter genes. One of these reporter genes was the BARNASE gene for targeted cell ablation. Our results indicate that FBP7 promoter activity is restricted to the seed coat of developing seeds and that it is completely silent in the gametophytically derived tissues. The mutants used in this study provided a unique opportunity to investigate one of the poorly understood aspects of seed development: the interaction of embryo, endosperm, and maternal tissues.