FGM1/rPPR4-dependent female gamete maturation is essential for seed development initiation in Arabidopsis

Gamete maturation is critical for fertility of both animals and plants; however, the molecular mechanisms underlying these processes remain poorly understood in plants. Here, we report the Female Gamete Maturation 1 (FGM1/rPPR4), a component of mitoribosome large subunit in Arabidopsis directly interacts with the mitochondrial protein GAMETE CELL DEFECTIVE 1 (GCD1) and plays an essential role in female gamete maturation and subsequent zygote-embryo transition and endosperm development. We reveal that FGM1/rPPR4, assisted by GCD1, is an essential factor for female gamete maturation. We also confirm that female gamete maturation is necessary for the capacity of post-fertilization zygote-embryo transition and endosperm development, but not for double fertilization, indicating that essential mechanisms are established during female gamete maturation to provide a molecular basis for seed development initiation and plant fertility.