Figure 7. Divergence-driving words for principal components.

We identified divergence-driving words for each of the principal components in Figure 6A. Few words are shared by the different principal components, suggesting that distinct sets of motifs and A-P regulators govern the different patterns of variation revealed by PCA. The CAGGTAG binding site for the early zygotic activator Zelda drives divergence of coherent binding of all factors (principal component 1). A red box in a (row, column) entry indicates that the corresponding word (row) was identified as a DDW for a particular principal component (column); a solid circle in a (row, column) indicates that a word (row) matches the DNA-binding specificity of a factor analyzed here, plus Zelda (column). In contrast to Figure 4, where empty circles are used to indicate matches to A-P factors other than the six analyzed here, no empty circles are shown here because all words match the specificities of one or more additional A-P regulators, as characterized by [29]. Sequence motifs and their reverse complements are shown in the row labels.