Alarms and diversions: the biochemistry of development.

In considering biochemical aspects of development over a range of different organisms--plants, animals, fungi and bacteria--some ubiquitous themes emerge. Many of the regulatory mechanisms being discovered in higher organisms have already been found in yeast, and there are examples of similar mechanisms in bacteria, notably, analogies and even homologies in multistep cascades involving phosphorylation and negatively acting steps; interplay between development and the cell cycle; and emerging evidence that metabolic pathways can be important developmental agents. On the other hand, those topics that remain resolutely organism-specific may serve as a warning to those who tend to overgeneralize, or as the nucleus for the next generation of general insights.