Available online: explore how the maternal-to-zygotic transition unfolds across brown algae with contrasting reproductive strategies. In this study, we profile early development in three species spanning the isogamy–oogamy continuum — Dictyota dichotoma, Undaria pinnatifida, and Scytosiphon promiscuus — using allele-specific expression across reciprocal crosses. Contrary to expectations from animal systems, we find that maternal provisioning does not delay zygotic genome activation. Instead, oogamous species activate their genomes rapidly after fertilisation in a single continuous wave, while the near-isogamous species shows a biphasic activation with a delayed major wave. Our results reveal that the timing of the maternal-to-zygotic transition is evolutionarily flexible and shaped by reproductive strategy rather than maternal investment alone.
https://doi.org/10.64898/2026.04.21.719843