Ovule-specific MADS-box proteins have conserved protein-protein interactions in monocot and dicot plants

Abstract

OsMADS13 is a rice MADS-box gene that is specifically expressed in developing ovules. The amino acid sequence of OsMADS13 shows 74% similarity to those of FLORAL BINDING PROTEIN 7 (FBP7) and FBP11, the products of two MADS-box genes that are necessary and sufficient to determine ovule identity in Petunia. To assess whether OsMADS13, the putative rice ortholog of FBP7 and FBP11, has an equivalent function, several analyses were performed. Ectopic expression of FBP7 and FBP11 in Petunia results in ectopic ovule formation on sepals and petals. Here we show that ectopic expression of OsMADS13 in rice and Arabidopsis does not result in the formation of such structures. Furthermore, ectopic expression of FBP7 and FBP11 in Arabidopsis also fails to induce ectopic ovule formation. To determine whether protein-protein interactions involving putative class D MADS-box proteins have been conserved, yeast two-hybrid assays were performed. These experiments resulted in the identification of three putative partners of OsMADS13, all of them encoded by AGL2-like genes. Interestingly the Petunia FBP7 protein also interacts with AGL2-like proteins. The evolutionary conservation of the MADS-box protein partners of these ovule-specific factors was confirmed by exchange experiments which showed that the protein partners of OsMADS13 interact with FBP7 and vice versa.

The AGL6-like gene OsMADS6 regulates floral organ and meristem identities in rice

“…It is possible that OsMADS6 interacts with other MADSbox protein(s) controlling rice flower development. In agreement with this hypothesis, OsMADS6 interacts with four SEP-like genes (OsMADS1, OsMADS5, OsMADS7 and OsMADS8), a B class gene (OsMADS16) and a D class gene (OsMADS13) in yeast cells [46][47][48]. Further genetic and biochemical analyses of the interaction of these genes with OsMADS6 will help to elucidate the mechanism of rice flower development.…”

“…In addition, OsMADS6 has a similar expression pattern to that of SEP genes [5,6]. Furthermore, OsMAS6 is able to form protein complexes with rice B and D proteins in yeast cells [47,48], resembling the complex formation of SEP proteins with A, B and C in Arabidopsis and other eudicot species [9,54]. Moreover, a physical interaction between BDE and ZAG1 (Zea AGAMOUS 1, a C class protein) in maize has also been shown recently [40].…”

Identification and Characterization of Four Chrysanthemum MADS-Box Genes, Belonging to the APETALA1/FRUITFULL and SEPALLATA3 Subfamilies

“…Similar higher order complexes were proposed for other MADS-box proteins involved in flower development (Honma and Goto, 2001), which recently led to the Quartet model for flower organ specification (Theissen, 2001). These complexes add a new dimension to the combinatorial ABCDE model and recent studies with petunia MADS-box proteins show that these interactions are conserved among angiosperm species (Favaro et al, 2002;Ferrario et al, 2003).…”

MADS-Box Protein Complexes Control Carpel and Ovule Development in Arabidopsis

“…Yeast two-hybrid protein interaction assays showed that the petunia proteins FBP7 and FBP11 interact with the SEP-like (AGL2-like) proteins FBP2, FBP5, and FBP9 . Interestingly, the rice MADS-box protein OsMADS13 also interacts with two SEP-like proteins, OsMADS24 and OsMADS45 (Favaro et al, 2002). The evolutionary conservation of the MADS-box protein partners was confirmed by yeast twohybrid exchange assays, which showed that the protein partners of FBP7 interact with OsMADS13 and vice versa (Favaro et al, 2002).…”