Variation in gene expression may underlie many important evolutionary traits. However, it is not known at what stage in organismal development changes in gene expression are most likely to result in changes in phenotype. One widely held belief is that changes in early development are more likely to results in changes in downstream phenotypes. In order to discover how much genetic variation for transcript level is present in natural populations, we studied zygotic gene expression in nine inbred lines of Drosophila melanogaster at two time points in development. We find abundant variation for transcript level both between lines and over time: close to half of all expressed genes show a significant line effect at either time point. We examine the contribution of maternally-loaded genes to this variation, as well as the contribution of variation in upstream genes to variation in their downstream targets in two well-studied gene regulatory networks. Finally, we estimate the dimensionality of gene expression in these two networks and find that—despite large numbers of varying genes—there only appear to be two factors controlling this variation. Keywords: Genetic variation and time course
Overall design
Two chips for each of nine isogenic lines sampled at two time points (=36 arrays).
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