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

Gamete maturation are 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) 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. FGM1/rPPR4 binds to mitochondrial ribosome 26S ribonucleic acid (RRN26) to fine-tuneensure mitochondrial translation and further impacts nuclear transcription, which is required for female gamete maturation. Thus, 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 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.