The evolution of plant regulatory networks: what Arabidopsis cannot say for itself

Genetic and molecular analyses in the dicot model plant Arabidopsis thaliana have begun to shed some light on regulatory networks in plants. However, comparisons with other species are necessary to validate networks identified in model species on the evolutionary scale. Many key regulatory proteins are encoded by members of transcription factor gene families. Orthologous genes can be identified by phylogenetic reconstructions based on conserved protein domains and functionally substantiated by gene expression patterns and mutant analyses. Recent comparative analyses of different pathways involved in shoot meristem development reveal not only conservation from basal land plants to angiosperms but also evolutionary freedom for significant adaptations in the course of plant speciation.