In a general screen for XX females in C. briggsae, we found three mutants that cause hermaphrodites to develop as females, but do not affect males. These alleles define a single gene,
glf-1. We isolate another four alleles in a non-complementation screen. Because all 7 alleles are temperature sensitive, we believe that loss of
glf-1 reveals an underlying temperature-sensitivity in sex determination. Since
glf-1 is only required for XX animals to develop as hermaphrodites, but plays no role in males, it functions much like
fog-2 in C. elegans. In C. elegans, FOG-2 contains both an F-box and an FTH domain, which is required to bind GLD-1, and GLD-1 binds the 3UTR of
tra-2 mRNA to inhibit translation. However, Tim Schedls group show that there is no a homolog of
fog-2 in C. briggsae, and that
gld-1 RNAi in C. briggsae has an unexpected Mog phenotype. Thus,
glf-1 probably controls germ cell fates by a novel mechanism. Since
glf-1 appears to be the key to hermaphroditic development in C. briggsae, we have been using SNP mapping to clone it. We narrowed its location down to a region between
cb17324 and
cb17358 on
cb25.
fpc2501. Three F-box genes are included in this region, RNAi against CBG11663 produce 95% Fog animals at 25C, but only 26% Fog at 15C. Furthermore, this RNAi phenotype can be suppressed by
tra-2(lf)/+, just like
glf-1 mutations. Thus, CBG11663 is likely to be
glf-1. We have sequenced cDNA and genomic DNA from
glf-1 mutants, and found a C to T transition in
v35 that causes a missense mutation, and another C to T transition in
v49 that creates a TAA stop condon. Both lesions occur in the F-box coding region. We cloned CBG11663 transcripts, and found that they are smaller than predicted by the Genome Sequencing Consortium, and that its 5-end is trans-spliced to SL1. Northern blots and RT-PCR show that
glf-1 expression level increases during development, and is strongest in adults, even though it is only required in L4 larvae. We propose that GLF-1 binds other proteins and catalyzes their degrading to down-regulate TRA-2 to allow spermatogenesis in XX L4 larvae.