plx-2(
ev773) enhances the embryonic lethality of
vab-1(
dx31) mutants (Table S2). "The genetic interactions of
plx-2 and
mab-20 with
vab-1 mutations in preventing pocket closure defects are more complex. For example, the
vab-1 null mutation enhances both the
plx-2 null and the
mab-20 null synergistically for embryonic lethality (this enhancement is largely synthetic) (Figure 5C)... The pattern of redundancies governing prevention of lethality (last four gray data bars to the right in Figure 5C) is nearly identical to the pattern of redundancies governing the prevention of gaps between sister plexin band cells (last four black data bars to the right in Figure 5B). This strongly suggests that the synergistic enhancement of
vab-1 mutant embryonic lethality by
plx-2 mutations is caused by the persistence of gaps between sister plexin band cells, which block migrating P9/10 cells from completing pocket closure. This interpretation is supported by cell-type-specific rescue data presented below and considered further in the Discussion."