Morphogen signaling contributes to the patterned spatiotemporal expression of genes
during development. One mode of regulation of signaling-responsive genes is at the
level of transcription. Single-cell quantitative studies of transcription have revealed
that transcription occurs intermittently, in bursts. Although the effects of many
gene regulatory mechanisms on transcriptional bursting have been studied, it remains
unclear how morphogen gradients affect this dynamic property of downstream genes.
Here we have adapted single molecule fluorescence in situ hybridization (smFISH) for
use in the Drosophila wing imaginal disc in order to measure nascent and mature mRNA
of genes downstream of the Wg and Dpp morphogen gradients. We compared our experimental
results with predictions from stochastic models of transcription, which indicated
that the transcription levels of these genes appear to share a common method of control
via burst frequency modulation. Our data help further elucidate the link between developmental
gene regulatory mechanisms and transcriptional bursting.