Understanding the Specification Mechanism of the Megaspore Mother Cell in Arabidopsis.

The megaspore mother cell (MMC) is the founding cell of the plant female germline, and its specification is a critical step in sexual reproduction of flowering plants. Recent advances in single-cell transcriptomics, live imaging, and gene editing have significantly advanced our understanding of the molecular mechanisms underlying MMC specification in Arabidopsis thaliana. Here, we systematically review the latest findings from three integrated perspectives. Cell-autonomous regulatory mechanisms that establish MMC fate; non-cell-autonomous signals originating from somatic cells that position and permit MMC specification; and mechanisms by which neighboring somatic cells maintain their own fate and restrict MMC number. We also outline key open questions and offer perspectives on future research directions. This review provides a comprehensive reference for understanding the molecular-level mechanisms governing female germ cell fate determination in plants.