DOWN-REGULATION OF OVULE-SPECIFIC MADS BOX GENES FROM PETUNIA RESULTSIN MATERNALLY CONTROLLED DEFECTS IN SEED DEVELOPMENT

A maternally determined seed defect has been obtained by downregulatio n of the petunia MADS box genes Floral Binding Protein7 (FBP7) and FBP 11. These genes have been previously shown to play central roles in th e determination of ovule identity. Aberrant development of the seed co at and consequent degeneration of the endosperm have been observed in transgenic plants in which these two genes are downregulated by cosupp ression. Analysis of the expression pattern of FBP7 and FBP11 and gene tic analysis confirmed the maternal inheritance of the phenotype. The FBP7 promoter was cloned and fused to reporter genes. One of these rep orter genes was the BARNASE gene for targeted cell ablation. Our resul ts indicate that FBP7 promoter activity is restricted to the seed coat of developing seeds and that it is completely silent in the gametophy tically derived tissues. The mutants used in this study provided a uni que opportunity to investigate one of the poorly understood aspects of seed development: the interaction of embryo, endosperm, and maternal tissues.