Practice question

SKN-1 specifies mesendodermal progenitors central to nematode gastrulation and gut formation. Maternal SKN-1 accumulates in EMS nucleus where it directly binds promoters of med-1,2 GATA factors, which activate end-1,3 and tbx-35 to segregate endoderm versus mesoderm lineages differentially. Null skn-1 alleles lack pharynx derived from MS, body wall muscle from MS, intestine derived from E, causing embryonic lethality with excess skin, neurons but no gut markers. Rescue shows autonomous requirement in EMS not P2. Thus loss mirrors mesendoderm deletion rather than vulval defects highlighting master regulator role.