During the maternal-to-zygotic transition (MZT), multiple mechanisms precisely control massive decay of maternal mRNAs. N⁶-methyladenosine (m⁶A) is known to regulate mRNA decay, yet how this modification promotes maternal transcript degradation remains unclear. Here, we find that m⁶A promotes maternal mRNA deadenylation. Yet, genetic loss of m⁶A readers Ythdf2 and Ythdf3 did not impact global maternal mRNA clearance, zygotic genome activation, or the onset of gastrulation, challenging the view that Ythdf2 alone is critical to developmental timing. We reveal that Ythdf proteins function redundantly during zebrafish oogenesis and development, as double Ythdf2 and Ythdf3 deletion prevented female gonad formation and triple Ythdf mutants were lethal. Finally, we show that the microRNA miR-430 functions additively with methylation to promote degradation of common transcript targets. Together these findings reveal that m⁶A facilitates maternal mRNA deadenylation and that multiple pathways and readers act in concert to mediate these effects of methylation on RNA stability.

在母体到合子的转变 （MZT） 期间，多种机制精确控制母体 mRNA 的大量衰变。已知 N⁶-甲基腺苷 （m⁶A） 可调节 mRNA 衰变，但这种修饰如何促进母体转录本降解仍不清楚。在这里，我们发现 m⁶A 促进母体 mRNA 脱腺苷化。然而，m⁶A 读者 Ythdf2 和 Ythdf3 的基因丢失并不影响整体母体 mRNA 清除、合子基因组激活或原肠胚形成的发生，挑战了 Ythdf2 单独对发育时间至关重要的观点。我们揭示了 Ythdf 蛋白在斑马鱼卵子发生和发育过程中发挥冗余作用，因为双 Ythdf2 和 Ythdf3 缺失阻止了雌性性腺的形成，而三重 Ythdf 突变体是致命的。最后，我们表明 microRNA miR-430 与甲基化相加功能，以促进常见转录靶标的降解。总之，这些发现揭示了 m⁶A 促进母体 mRNA 脱腺苷化，并且多个通路和读取器协同作用以介导甲基化对 RNA 稳定性的这些影响。