Plant MADS‐box genes encode transcriptional regulators that are critical for a number of developmental processes. In the angiosperms (the flowering plants), these include the specification of floral organ identities, flowering time and fruit development. It appears that the MADS box gene family has undergone considerable gene duplication and sequence divergence within the angiosperms. Here I discuss the possibility that these events have allowed the recruitment of these genes to new developmental pathways in particular angiosperm lineages. Recent analyses of sequence changes, (...) expression patterns and, in a few cases, gene function are beginning to provide tantalizing evidence for deciphering when and how such genetic diversification has led to particular morphological innovations. In the future, comparative studies of large numbers of species will be required to assess the extent of such variation as well as to fully understand the mechanisms by which evolution of these developmental regulators has played a role in shaping new morphologies. BioEssays 25:637–646, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

There is increasing evidence for the wide‐spread existence of functionally redundant genetic pathways in developmental processes. However, both their significance and manner of evolution are still matters of debate. I will argue here that redundancy of gene actions may, in fact, be a necessary requirement for the development and evolution of complex life forms. One can view development as a process that transmits information from the egg to the adult organism. Transmission of information is, however, always an error‐prone process, which (...) can only be safeguarded by including redundancies in the message. Molecular examples for well analysed redundant processes indicate that redundancies may best be understood within a conceptual framework of overlaps between different gene functions. (shrink)

The phenomenon of ‘canalization’ ‐ the genetic capacity to buffer developmental pathways against mutational or environmental perturbations ‐ was first characterized in the late 1930s and early 1940s. Despite enormous subsequent progress in understanding the nature of the genetic material and the molecular basis of gene expression, there have been few attempts to interpret the classical work on canalization in molecular genetic terms. Some recent findings, however, bear on one form of canalization, ‘genetic canalization’, the stabilization of development against mutational (...) effects. These data indicate that co‐expressed paralogous genes can function as mutual ‘back‐up’ elements in developmental processes. Paralogues, however, are far from the only basis of canalization: other genetic sources can be readily envisaged and some of these are described here. The evolutionary questions about genetic canalization and the mechanistic questions about developmental instability that still need to be addressed are also briefly discussed. (shrink)