Reduced expression of mitochondrial targeted RecA causes phenotypic differences in Arabidopsis

Abstract

Animals, yeast, and plants have similar numbers and types of genes expressed in their mitochondrial genomes. One difference, however, is that plants, specifically Arabidopsis, contain highly branched linear DNA whereas animals have circular DNA and yeast have both linear and circular mitochondrial DNA (mtDNA). We propose that mitochondrial targeted RecA is essential for mtDNA recombination and is responsible for forming the observed branching of mtDNA. We have observed differences in growth rate and plant morphology in Arabidopsis mutants that contain either a transfer DNA insertion or single base mutation in the nuclear encoded mitochondrial targeted RecA gene. The organization of the mitochondrial cristae is decreased when these mutants are observed by transmission electron microscopy. These morphological differences correspond to a decrease in RecA protein expression observed by western blot. The relative abundance of DNA in the mitochondrion is decreased when examined with quantitative PCR. When these mutant plants are challenged under DNA damaging conditions the differences are magnified. We conclude that mitochondrial RecA is essential for normal plant and mitochondrion morphology and may be involved in mtDNA replication and repair. This research was funded by the NIH.