CGF1 and CGF2 jointly participate in iron homeostasis in chloroplasts.

Iron (Fe) plays a crucial role in chloroplast function, and its deficiency results in Fe chlorosis, a syndrome characterized by reduced biomass production and plant mortality. In this study, Fe supplementation rescued the dwarfism and chlorotic phenotype of cgf1 cgf2 mutant, suggesting that CGF1 and CGF2 are essential regulators of Fe homeostasis. Subcellular localization analysis revealed that both CGF1 and CGF2 localize to the chloroplast envelope. Their absence led to a decreased photosynthetic protein abundance and reduced photosynthetic supercomplex levels, demonstrating that CGF1 and CGF2 are important for photosynthetic protein accumulation and the assembly or stabilization of photosystem complexes. Furthermore, cgf1 cgf2 leaves exhibited hydrogen peroxide (H2O2) accumulation and upregulated expression of oxidative stress-responsive genes, confirming oxidative stress occurrence in the mutant. Interaction assays revealed that CGF1 and CGF2 interact with PIC1, a chloroplast Fe importer, suggesting their cooperative function in maintaining chloroplast Fe homeostasis. These findings indicate that CGF1 and CGF2 mediate Fe transport at the chloroplast envelope, supporting photosynthesis, plant growth, and development.