A recent volume of this series (Signals and Signal Transduction Pathways in Plants (K. Palme, ed.) Plant Molecular Biology 26, 1237-1679) described the relay races by which signals are transported in plants from the sites of stimuli to the gene expression machinery of the cell. Part of this machinery, the transcription apparatus, has been well studied in the last two decades, and many important mechanisms controlling gene expression at the transcriptional level have been elucidated. However, control of gene expression is by no means complete once...