The potential of the WRKY gene family for phylogenetic reconstruction: an example from the Malvaceae.

The WRKY gene family of transcription factors is involved in several diverse pathways and includes components of plant-specific, ancient regulatory networks. WRKY genes contain one or two highly conserved DNA binding domains interrupted by an intron. We used partial sequences of five independent WRKY loci to assess their potential for phylogeny reconstruction. Loci were originally isolated from Theobroma cacao L. by PCR with a single pair of degenerate primers; loci-specific primers were subsequently designed. We tested those loci across the sister genera Herrania Goudot and Theobroma L., with Guazuma ulmifolia Lam. as the outgroup. Overall, the combined WRKY matrices performed as well or better than other genes in resolving the intrageneric phylogeny of Herrania and Theobroma. The ease of isolating numerous, independent WRKY loci from diverse plant species with a single pair of degenerate primers designed to the highly conserved WRKY domain, renders them extremely useful tools for generating multiple, single or low copy nuclear loci for molecular phylogenetic studies at lower taxonomic levels. This is the first demonstration of the potential for members of the WRKY gene family for phylogenetic reconstruction.