In wild-type germlines, SYP-1 is dependent on HIM-3 for association to chromosomes and first appears as aggregates and bright stretches in the same leptotene-zygotene nuclei in which HIM-3-marked axes are assembling. SYP-1 localizes to both stretches of HIM-3 and to a subset of HIM-3 foci, but is always less abundant than HIM-3 at chromosome axes at this stage. In the absence of HIM-3, the precocious association of SYP-1 to chromosome cores during leptotene zygotene in
htp-1 mutants was abrogated.