Worm Breeder's Gazette 9(2): 94

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Some Surprising Sexual Suppression by Morphogenetic Mab Mutations

J. Hodgkin

Mutations of the gene tra-3 IV cause partial masculinization of XX 
animals.  A total of 42 extragenic suppressors of tra-3 have been 
isolated and analyzed (see WBG 8-2: 46; Genetics 111: 287).  Most of 
these cause feminization of XX or XO animals when crossed into a tra-3(
+) background.  These feminizing suppressors are all mutations of sex-
determining genes: gain-of-function alleles of tra-1 (11 alleles) or 
tra-2 (one allele), or loss-of-function alleles of fem-1 (4 alleles), 
fem-2 (4 alleles) or fem-3 (18 alleles).
The remaining suppressors are recessive weak suppressors without 
obvious feminizing effects.  They identify four new 
1) sup(e1992) IV maps between unc-30 and tra-3; ts sterile phenotype.
2) sup(e2042) IV maps between dpy-20 and unc-30; no other phenotype. 
3) egl-48(e1952) II is tightly linked to sqt-3; XX animals Egl-4) 
008) I is close to bli-3; XO animals Mab.
The last suppressor, e2008, has a 'morphogenetic Mab' (male abnormal)
phenotype; mab-11 XO males have swollen bursae, reduced fans and 
shortened rays.  Nevertheless, all male structures (e.g.  copulatory 
spicules) are present and the abnormal males can sometimes mate 
successfully.  Mab-11 XX hermaphrodites have swollen vulvae, and are 
sometimes Egl.  These phenotypes are very similar to those of some 
other mab mutations, particularly mab-1 alleles.  A double mutant, mab-
1(e1228); onstructed and found to show 
similar suppression to mab-11.  This makes it likely that mab-11(e2008)
is a pleiotropic single mutation, rather than a double mutant.  Both 
amber (e1107) and non-amber (e1767) alleles of tra-3 are suppressed by 
mab-11.  Also, tra-2(e1209) (a weak tra-2 allele with a phenotype 
similar to tra-3) is partly suppressed by mab-11.The egl-48 suppressor 
may be related to mab-11 and mab-1, in that egl-48 XO males sometimes 
have swollen bursae, and the Egl phenotype in the XX hermaphrodite 
seems to result from a vulval morphogenesis defect.  Several other mab 
mutations affect morphogenesis (as opposed to lineage) of the bursa, 
and sometimes of the vulva too: mab-4, mab-7, 
ere tested for the ability to 
suppress tra-3; none of them had any effect (nor did the 'lineage 
mabs', mab-3 and mab-9).These suppression effects are minor, but 
striking.  I don't have any attractive explanations at the moment.