The ABC model of floral organ development proposes combinatorial interaction of A, B, and C class genes whereby these three classes of genes specifies the four floral organs, sepals, petals, stamens, and carpels. A class genes specify sepal identity, A plus B class genes specify petal identity, B plus C class genes specify stamen identity, and C class genes specify carpel identity. Many of the genes involved in the ABC model are members of the MADS box gene family. The ABC model has been primarily characterized in Arabidopsis and Antirrhinum. Significantly, the B and C functions of this model also extend to maize (Zea), although functional conservation of the A function remains to be demonstrated. Nevertheless, the strong genetic and molecular evidence for the conservation of at least portions of the ABC model suggests that this is an ancient regulatory network, perhaps applicable to most angiosperms. However, various modifications of the specific components of the ABC model may have occurred in different lineages of angiosperms. We have developed a protocol that permits the extraction of quality RNA from small amounts of tissue from a wide range of angiosperms. Using this approach, we have extracted RNA from young flowers, as well as floral organs at various stages of development from the basal angiosperms Nuphar (Nymphaeaceae) and Illicium (Illiciaceae). We have isolated MADS-box genes from Nuphar and Illicium and present phylogenetic analyses as well as preliminary expression analyses of these genes.

Key words: ABC model, basal angiosperms, MADS-box genes, RNA isolation