Practice question

SKN-1, maternally provided bZIP transcription factor related to Nrf, accumulates in P1 and later EMS blastomere due to PAR polarity and SKR-mediated regulation. It directly binds promoters of med-1, med-2 GATA factors, initiating mesendoderm program that subsequently activates end-1, end-3 and tbx-35 for E versus MS divergence. skn-1 mutants lack pharynx and intestine derived from EMS, with EMS transforming to C-like muscle fate. It does not regulate LIN-39 or vulval signaling, but serves as earliest zygotic activator connecting maternal polarity to zygotic endomesoderm specification, upstream of Wnt-modified POP-1 decision mechanism.