Fig. 6. GLD-1 restricts MEX-3 expression to the distalmost germ cells, where MEX-3 represses translation of RME-2. (A) Control heterozygous gld-1/+ animal showing MEX-3 restricted to the distalmost, mitotic region, as in wild-type gonads (compare with Fig. 5E). (B) gld-1 mutant gonad showing MEX-3 in both the distal and medial regions of the gonad. In tumorous gld-1 gonads, germ cells that leave the distalmost region enter pachytene and then re-enter mitosis. MEX-3 is expressed throughout the gld-1 germline, including in the pachytene cells, suggesting that its broad expression is not due simply to re-entry of germ cells into mitosis. Similarly, gld-1;atx-2(RNAi) gonads are not tumorous and express MEX-3 inappropriately in meiotic germ cells (D). (E) Model showing rme-2 mRNA at very low levels (gray) in the distalmost gonad and increasingly high levels (black) in the medial gonad. GLD-1 restricts MEX-3 expression to the distalmost gonad, where MEX-3 prevents the low levels of rme-2 mRNA from being translated. (F) RME-2 is translated in the distalmost part of masculinized gld-1;atx-2(RNAi) germline, but not in the control fem-3(gf) masculinized germline. Removal of GLD-1 alone from either male germlines or from masculinized hermaphrodite germlines, does not result in the distalmost expression of RME-2. Depletion of GLD-1 from atx-2(RNAi) germline restores the distalmost, mitotic region of the germline. (G) Masculinized germlines of gld-1;atx-2(RNAi) and fem-3(gf) animals have similar, low levels of rme-2 mRNA in the distalmost germline (brackets). (H-J) Gonad from a glp-1(gf);atx-2(RNAi) animal stained with DAPI (H), for MEX-3 (I) and RME-2 (J). MEX-3 is present throughout the gonad, but is unable to repress RME-2. Scale bars: 50 µm.