Functional Evolution of a cis-Regulatory Module
Figure 3
Developmental Series of EVE Abundance
(A–E) Immunofluorescence labeling of time-staged early EVEΔS2E homozygous embryos. This developmental sequence, which corresponds roughly from the initialization of cellularization (A) to its completion (E), takes approximately 45 min at 25 oC in wild-type flies [41].
(F) Expression of en in same genotype at stage 10. Arrows mark third and fourth en stripes. Note the short interval between en stripes 3 and 4 (parasegment 3) and the reduced fourth stripe.
(G) EVE expression in stripe 2 during the developmental series around cellularization, where times 1–5 correspond to pictures in A–E. Stage 1 is early cellularization, while the process has been completed for embryos in class 5. The series is comparable to time classes 4–8 on the FlyEx Web site (http://flyex.ams.sunysb.edu/flyex/) [34]. Estimated least square means (± SE) for EVEΔS2E/Cy stock and wild-type line w1118; note the Cy/Cy homozygote is essentially wild-type. Early eve pair-rule expression is not known to be autoregulated (as occurs in postcellularization stages), and we observe a 2-fold difference in early stripe expression, with an additive component (a) of 0.62 and negligible dominance deviation (d/a) = 0.01, for the first two stages. This dosage dependency is lost after the cellularization stage (3), presumably because all embryos carry two copies of the autoregulatory element.