Origin and Diversification of Flowers
A few of the things we have learned from the Floral Genome Project include: 1) The floral transcriptome is large - estimated to contain over 10,000 expressed genes in basal as well as more derived dicot and monocot model organisms. Surprisingly, statistical estimates (Wang et al., 2005) suggest that the transcriptome may even be larger in basal angiosperms than in more derived monocot and eudicot species that have a fixed pattern of flower development. 2) Most key genes playing known roles in flower development have homologs present in basal angiosperm lineages (Albert et al., 2005) and may be inferred to be part of the ancestral flower transcriptome. The ancestral features of these gene families and proteins can be inferred. 3) Genome doubling (polyploidy) appears to be a common process in plant genomes, including these most basal lineages (Cui et al. 2006). 4) Consistent with the above, specific genes of known function, including the MADS box development regulators (Zahn et al., 2006), are often the product of one or more gene duplications that separate basal lineages from more derived eudicot and grass models. 5) New statistical approaches that have allowed us to dissect the pattern of expression change following gene duplication show that virtually all retained paralogous pairs of regulatory genes do show altered gene expression patterns (Duarte et al., 2006) of a kind that would support gene retention. 6) Despite the fact that plant genomes have undergone many genome doubling events and complex gene families are typical, a few hundred genes have consistently remained single copy and have common and often highly predictable roles across angiosperms and seed plants. This set of genes is not only interesting from a molecular and functional perspective, they are valuable genetic markers for studying plant phylogeny. To learn more about the entire FGP project, our collaborators, and students, please visit the FGP project homepage (http://www.floralgenome.org).
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