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Fig. 1. Evolutionary divergence of eggshell morphology and rho
expression pattern between D. melanogaster and
D. virilis. (A) The egg of D.
virilis has four DAs, an ancestral trait, as found in the
Hirtodrosophila outgroup of the genus Drosophila. The two
DAs found in D. melanogaster is a more recently evolved trait. D.
virilis and D. melanogaster diverged 40-60 million years ago
(mya). (B,C) The eggshells of D. melanogaster (B) and
D. virilis (C) are shown with anterior to the left (dorsal view).
(D,E) Schematic comparison of the rho expression
patterns between D. melanogaster and D. virilis during
oogenesis. Dorsal lateral views of stage 10A- to 12-egg chambers are shown
with rho expression (blue). Anterior is to the left. (D) D.
melanogaster rho was expressed in a saddle-shaped zone at the dorsal
anterior at stage 10A. This expression was refined into an L-shaped stripe on
either side of the dorsal midline at stage 10B. Expression was then restricted
to the anterior row lacking the midline region at stage 11, as it continued
until stage 12. (E) D. virilis rho was expressed in two domains at
the dorsal-lateral sides at stage 10A. No expression occurred in the midline,
unlike in D. melanogaster. The expression was repressed at the
posterior region and refined into a Vshaped stripe missing its apex at stage
10B. Expression was upregulated at the front and rear of each stripe, and
expression in the rear moved anteriorly at stage 11. Subsequently, the
expression was divided into four domains at stage 12, corresponding to the
positions of the four DAs.
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