Lineage motifs and reuse of anterior-posterior expression logic. (A) ceh-16 and pax-3 reporters are expressed in multiple sublineages. The diagrams are organized according to the conventions of Sulston et al. (1983), with time on the vertical axis, divisions represented by horizontal lines, and the anterior daughter placed in the left position of each division. Red intensity is displayed proportional to the measured fluorescence signal. Arrowheads mark inferred commitment points (Color of arrowheads: [red] identified using the fivefold difference in lineage average criterion used for Supplemental Table 5 and described in detail in the methods; [blue] lineages below the fivefold cutoff identified by manual inspection, actual fold difference for these cases was between threefold and fivefold). In one of three pax-3 replicates, additional weak expression below our threshold was observed in the (posterior-derived) ABarp lineage, and the ceh-16 reporter was expressed at low levels (also well below the threshold) in the additional posterior-derived lineage ABprappp. (B) Three dimensional projections of confocal micrographs show the terminal positions of expressing cells for the reporters shown in A are distributed over the full length of the embryo. (C) Histogram showing that reporters differentially expressed in three or more lineages (black bars, using the fivefold lineage-based cutoff) are biased toward mostly anterior or mostly posterior lineages relative to randomized control (white bars). (D) Identification of lineage motifs. (Left) Example showing mapping of egl-5 reporter expression (top) onto a binary two-division pattern (bottom). (Right) Frequency of 2-division and 3-division lineage patterns. (E) Examples of A–P patterns in the lineage derived from the C founder cell. In some cases lineage patterns are correlated with tissue identity (nhr-171) or position (lin-39). (F) Changes in reporter expression after pop-1 RNAi. tlp-1 and ceh-27 show ectopic expression in the anterior lineage (a→p conversion), tlp-1 and elt-6 show both gain of anterior expression and loss of posterior expression.
