Closely related MADS-box genes in club moss (Lycopodium) show broad expression patterns and are structurally similar to, but phylogenetically distinct from, typical seed plant MADS-box genes

Abstract

The relation between the duplication history of the MADS-box gene family of transcription factors and the evolution of plant development is investigated here. The lycopsids, for example the club mosses, constitute the sister group of all other vascular plants, and are therefore interesting from this perspective. PCR-based methods were used to isolate MADS-box genes from the club moss, Lycopodium annotinum. In contrast to the previously isolated L. annotinum MADS-box gene LAMB1 (which also contains a so-called K-box), the new L. annotinum genes LAMB2, LAMB4, LAMB6 are structurally similar to most MADS-K-box genes. These genes, and two L. annotinum MADS-box genes, not encoding K-domains, LAMB3 and LAMB5, form a clade distinct from LAMB1. LAMB1 is expressed exclusively in the strobilus unlike LAMB2, LAMB4, LAMB5 and LAMB6, which are expressed in a broad range of organs. The results imply that the diversification of organ identity MADS-box genes occurred after the split of the lycopsids from the other vascular plants, and that lycopsids have a MADS-box gene family of a type primitive for land plants.