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

Abstract

A maternally determined seed defect has been obtained by downregulation of the petunia MADS box genes Floral Binding Protein7 (FBP7) and FBP77, 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 FBP 7 and FBP 7 7 and genetic analysis confirmed the matemal inheritance of the phenotype. The FBP 7 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 FBP 7 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.

Redefining C and D in the Petunia ABC

“…Nevertheless, we found that female fertility was dramatically decreased in these lines. However, repeated pollinations occasionally do lead to seed set, but the seeds that developed are fewer and larger and always have a shriveled/wrinkled seed coat ( Figure 6B), as observed earlier in milder FBP7/FBP11 cosuppression lines (Colombo et al, 1997). This indicates that the FBP7/11 gene pair does have a unique function in seed development that cannot be taken over by the other AG clade members.…”

“…Likewise, the seed development phenotype in our fbp7 fbp11 mutants and in the weaker cosuppression lines (Colombo et al, 1997) indicates a unique function for the petunia D-clade genes during seed development. Thus, MADS13, the rice ortholog of STK and FBP7/11, seems to be so far the only D-clade gene that is absolutely required for ovule identity (Dreni et al, 2011).…”

“…The two petunia D-clade genes FBP7 and FBP11 have been studied via cosuppression and ectopic expression Colombo et al, 1995Colombo et al, , 1997. Based on those studies, an extension of the ABC model with a D-function was proposed, in which the D-function genes are required for ovule identity specification.…”

“…Cosuppression lines in which both D-clade genes FBP7 and FBP11 are knocked down show a transformation of ovules into carpellike organs , leading to the addition of a Dfunction to the ABC model, for ovule identity specification. Later analyses suggested that the role of FBP7 and FBP11 may not be restricted to ovule identity specification; they also play a role in ovule differentiation and seed development (Colombo et al, 1997). Arabidopsis has one D-function gene, SEEDSTICK (STK), which plays a role in seed abscission and funiculus development (Pinyopich et al, 2003), while all AG subfamily members from Arabidopsis have (partially) redundant functions in ovule development. In the original ABC model, maintenance of B-gene expression was thought to be independent of the C-function.…”

Isolation and characterization of the papaya MADS-box E-class genes, CpMADS1 and CpMADS3, and a TM6 lineage gene CpMADS2

“…B-and C-class genes control anther development, and C-class genes also determine carpel differentiation (Weigel and Meyerowitz, 1994). In addition to the ABC model of floral control, a D-class MADS-box genes was found to control ovule differentiation, as in Petunia hybrida (Angenent et al, 1995a,b;Colombo et al, 1995Colombo et al, , 1997. Recent studies revealed that SEPALLATA1/2/3 (SEP1/2/3) may interact with members of other MADS-box genes to regulate petal, stamen, and pistil development; therefore, these were grouped into Eclass genes.…”