Fig. 1. Pigmentation phenotypes and enzymatic pathway in the Sophophora subgenus.

(A) Extant species that represent the inferred diversification of abdominal pigmentation from an ancestral monomorphic state to a derived dimorphic state in the Sophophora subgenus. The tergites covering the A5 and A6 abdominal segments of D. melanogaster and D. biarmipes are sexually dimorphic for a melanic pigment color, with the male tergites being fully pigmented and pigmentation limited to posterior stripes in females. The more distantly related species such as D. pseudoobscura and D. willistoni are monomorphic, though differ greatly in the extent of their melanization. (B) The production of yellow and black cuticle depends on the activity of a metabolic pathway converting Tyrosine into NβAD sclerotin or Dopa/Dopamine melanin. (C and C’) The wild type abdomen pigmentation pathway includes a male-specific pattern of fully melanic A5 and A6 segment tergites. (D and D’) RNA-interference for pale results in a near complete absence of black cuticle and a reduction in yellow cuticle color. (E and E’) RNA-interference for Ddc results in a stark reduction in black cuticle color and a reduction in yellow color. (F and F’) The null allele phenotype for yellow is a loss of black cuticle color. (G and G’) The hypomorphic allele phenotype for tan is a reduction in black cuticle color though the stripe and midline spot region pigmentation remains. (H and H’) The null allele phenotype for ebony is a broadening of black cuticle to all abdomen segments. RNA-interference was achieved by driving a UAS-regulated dsRNA transgene for pale and Ddc by the GAL4 transcription factor that was expressed in the dorsal-medial pattern of the pnr gene.