Transcriptional regulators and the evolution of plant form

Abstract

The modern or neo-Darwinian theory of evolution was formulated well over half a century ago at a time when genes were abstractions and development was understood only as the transition between a series of phenotypic states. Since that time, our knowledge of the gene, the diversity of types of genes, the interactions among genes, and the organization of genes into the networks and hierarchies that regulate development has grown enormously. Although still incomplete, this burgeoning knowledge of the molecular mechanisms that regulate ontogeny compels a continual reassessment of the question: How did the diversity of forms of life on earth evolve? Darwin resolved this question at the ecological level by explaining how natural selection would favor the “fittest” forms within a specific environmental context. The neo-Darwinian synthesis resolved this question at the genetic level by showing how the mechanisms of mutation, selection, and drift produce the directional changes in gene frequencies that underlie the evolution of novel forms (Huxley, 1963). The challenge facing the current generation of evolutionary biologists is to resolve this question at the molecular and developmental levels.