How do genomes encode developmental time?

It is a pleasure to contribute this short perspective to commemorate Terri Grodzicker's remarkable 35 years as Editor of Genes & Development, one of the foremost journals at the interface of gene regulation and developmental biology. The Levine lab has published 30 papers in G&D during Terri's tenure, and her generous stewardship of these papers attests to her patience, humor, and breadth of scholarship. These studies span gene expression in the early Drosophila melanogaster embryo, post-transcriptional processes such as alternative polyadenylation, and the role of gene regulatory networks in the specification of different cell types in the tadpoles of the sea squirt Ciona intestinalis. Our heartfelt thanks to Terri for her hard work in improving the quality of our papers over the years.

We can't let Terri skedaddle without bugging her one last time. Most of our earlier papers focused on the spatial control of gene expression in development (e.g., Doyle et al. 1989; Small et al. 1991). In addition to summarizing some of this work, we wish to share a couple of thoughts about an enduring challenge in developmental biology; namely, the temporal control of gene activity. We briefly summarize three potential genome structural mechanisms that modulate the timing of transcription during development: gene length, enhancer proximity, and tethering elements.