The C. elegans XX Hermaphrodite Germline Sex Determination Pathway

<div><p>(A) Genetic pathway for gene activity, where arrows represent positive regulation and bars represent negative regulation. The key genes <i>tra-2</i> and <i>fem-3</i> and the upstream regulators of <i>tra-2</i> that are the focus of this work, <i>fog-2</i> and <i>gld-1,</i> are in large bold font. The upstream genes <i>fog-2</i> and <i>gld-1,</i> which are key regulators of <i>tra-2</i> and addressed in this work, are also in large bold font. The gene activities at each level in the hierarchy are indicated below as “ACTIVE” in bold or “inactive” in grey. In L3 and L4 hermaphrodites the activities of <i>fog-2</i> and <i>gld-1</i> are high, leading to repression of <i>tra-2</i> activity (also see [B]) and the de-repression of <i>fem-3,</i> resulting in the onset of spermatogenesis. In L4 and adult hermaphrodites the activity of <i>fog-2</i> and <i>gld-1</i> are low, leading to high <i>tra-2</i> activity and the repression of <i>fem-3,</i> resulting in oogenesis. The shift in <i>tra-2</i>/<i>fem-3</i> balance allows for the switch from spermatogenesis to oogenesis in an otherwise female somatic gonad in the hermaphrodite.</p> <p>(B) C. elegans FOG-2/GLD-1/<i>tra-2</i> mRNA ternary complex. Current data indicates that FOG-2 and GLD-1 are required for the translational repression of the <i>tra-2</i> mRNA [<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0030006#pbio-0030006-b25" target="_blank">25</a>]. GLD-1 binds as a dimer to the <i>tra-2</i> mRNA 3′UTR at two 28 nucleotide direct repeat elements (TGE/DRE, blocks) and FOG-2 makes contact with GLD-1 [<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0030006#pbio-0030006-b32" target="_blank">32</a>,<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0030006#pbio-0030006-b34" target="_blank">34</a>]. All three components are required for the proper specification of hermaphrodite spermatogenesis.</p>