Mutants in the Fe-S biogenesis component AtDRE2 develop twin embryos and are defective in DNA demethylation in the vegetative phase

Iron is assembled inside cells into cofactors, essential for biological functions. Two types of cofactors, Iron Sulfur clusters and diferric tyrosyl radicals, share a conserved assembly complex containing the DRE2 enzyme, essential for cell viability in eukaryotes. In the model plant Arabidopsis thaliana, dre2 mutants are lethal, having a maternal defect related to active DNA demethylation in the central cell gamete and a zygotic defect leading to embryo arrest. However, neither of these defects is fully penetrant. We were able to recover the first dre2 viable mutants ever reported in plants by expressing DRE2 from a central cell specific promoter in a dre2 heterozygote background. The viable dre2 mutants developed twin embryos infrequently and were defective in DNA demethylation in the vegetative phase. These mutants represent a valuable tool to uncover further processes dependent on Iron containing cofactors from plants that may also be universal.