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Fig. 1. tra-1 controls gonadal symmetry. (A-D) Left, DIC images; right, immunofluorescence of same gonad in which (A,B) lag-2::GFP marks SGPs (Blelloch et al., 1999) and (C,D) GFP::POP-1 marks SGPs and their daughters. (A) Gonadal primordium in wild-type XO male with SGPs (Z1 and Z4) at poles and PGCs located centrally. (B) Gonadal primordium in tra-1(e1099) XX pseudomale, Z4 is dorsal and more anterior than normal. (C) Wild-type XO male, Z1 divides asymmetrically to produce Z1.a, which is smaller and has less nuclear GFP::POP-1 (small arrowhead); and Z1.p, which is larger and has more GFP::POP-1 (large arrowhead), a phenomenon also seen in hermaphrodites (Siegfried et al., 2004). In this gonad, Z4 has not divided. (D) tra-1(RNAi) XX pseudomale, polarity of Z1 division is reversed: Z1.a is larger and has more nuclear GFP::POP-1 (large arrowhead), while Z1.p, which is smaller, has less GFP::POP-1 (small arrowhead). In this gonad, Z4 has not divided and is located more dorsal and anterior than normal. (E,F) Z1/Z4 asymmetric divisions. (E) In wild-type males, central daughters (Z1.p/Z4.a, dark) are larger than polar daughters (Z1.a/Z4.p, light). (F) In tra-1 mutants, the polarity of Z1 division is reversed, so its polar daughter is larger (Z1.a, dark) than its central daughter (Z1.p, light), but the Z4 division has its normal polarity. (G,H) Laser ablation experiments test the fate of SGP daughters. In each experiment, three out of four SGP daughters were ablated (X), leaving one daughter to be assessed for fate. (G) In wild-type males, isolated Z1.p generated a linker cell (LC, n=1), while isolated Z1.a generated a distal tip cell (DTC, n=1). (H) In tra-1 mutants, isolated Z1.p generated a DTC (n=2), while isolated Z1.a generated a LC (n=6).

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