Studies in Floricaula/LEAFY Gene Phylogeny in Basal Angiosperms and Spore Bearing Plants

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9964374FrohlichOur work has shown that the homeotic gene Floricaula/LEAFY (LFY) can provide very strong evidence on phylogenetic relationships of major plant taxonomic groups. This is due mostly to the slow rate of change of the amino acid sequence of the gene, and partly because a gene duplication cut a "long branch" early in the evolution of seed plants. We will obtain LFY sequences to address relationships among 1) the major spore bearing groups (leptosporangiate ferns, Botrychium (of the Eusporangiate ferns), horsetails, Psilotum and seed plants, and perhaps also liverworts, mosses and lycopods and 2) the basal flowering plant groups, including such plants as waterlily, Magnolia, Drimys Ceratophyllum, etc. Our most parsimonious gene tree shows the duplication event preceding the separation of the flowering plant lineage. If true, this would mean flowering plants originally had a second copy of the LFY gene, which was subsequently lost. This observation suggests an alternative theory of flower evolution, based on developmental genetics. This part of the gene tree is uncertain, however, making the theory weakly supported. The same sequence data needed for phylogenetic analysis of the major plant groups should also more firmly establish the order of splittings in the gene tree. This may show, with more certainty, whether the duplication preceded the divergence of flowering plants, and so whether flowering plants had a second LFY gene that was lost.