Figure 4.—
Silencing or misexpression of Mdtra causes complete sex transformations in the housefly. Experiments were conducted with the MIII bwb+/ bwb strain to allow rapid and easy phenotypic distinction between M-bearing individuals (bwb+) and no-M individuals (bwb) (see materials and methods). Phenotypically, males can be recognized by a significantly narrower interocular distance. Also, males display a darkly pigmented copulatory apparatus (arrowhead) and exhibit characteristic horn-like structures (h) at the tip of sternite 5. The external female genitalia are characterized by the presence of an ovipositor (op). (A–H) Female–male sex reversion caused by injections of Mdtra dsRNA into syncytial embryos. (A) Head and (B) genital region of a control female (bwb) and (G and H) of a control male (bwb+), respectively, are shown. (C and D) Intersexual no-M individual (bwb) treated with Mdtra RNAi displaying a male-like interocular distance and sexually mixed genitalia composed of an almost complete ovipositor and a male-like sternite 5 with hornlike structures. (E and F) Completely sex-reverted no-M individual treated with Mdtra RNAi displaying normal male morphology in the head and genital region. (I–L) Male–female sex reversion caused by transgenic expression of MdtraF1. (I and J) Head and genital region of a nontransgenic control male (bwb+). (K and L) Complete feminization of an M-bearing individual (bwb+) after heat-induced induction of MdtraF1 expression. This fertile individual displays normal female morphology in the head and genital region. (M) Mddsx splicing patterns in sex-reverted individuals. Transcripts of Mddsx are analyzed by RT–PCR with primer pairs specific for the male splice variants (lanes 1, 3, 5, and 7) and the female splice variants (lanes 2, 4, 6, and 8). Total RNA was extracted from single flies: control female (lanes 1 and 2), control male (lanes 3 and 4), no-M individual (bwb) treated with Mdtra RNAi (lanes 5 and 6; see also E and F), and M-bearing individual (bwb+) expressing the MdtraF1 transgene (lanes 7 and 8; see also K and L).