Figure 1.

Sequence comparison among M-domain proteins from plants, indicating the conserved domain structures. Conceptual amino acid sequences of MADS-box genes from Ceratopteris (CRM) were aligned to one representative of each of the different subfamilies of M-domain proteins from plants that have been identified up to now (4). A “<” sign at the beginning of some sequences indicates that they are incomplete at the N terminus because of the cloning procedures used. The M-, I-, K-, and C-domains are indicated. In the region of the K-domain, hydrophobic amino acids (L, I, V, and M) are shown in bold, and positions in which more than 75% of the sequences have a hydrophobic residue are marked by a star. The complete names of the fern genes are CRM1;Ce.ric, CRM3;Ce.ric, CRM2;Ce.pte, CRM4;Ce.pte, CRM5;Ce.pte, CRM6;Ce.pte, and CRM7;Ce.pte, which indicate their origin from different Ceratopteris species (richardii and pteroides, respectively) in accordance with recent guidelines to naming sequenced plant genes (14).