Researchers of the radiotherapy group at institute of Modern Physics, Chinese Academy of Sciences (IMP) revealed the mechanism involved in the IR-induced mtDNA replication in Scientific Reports, a new multidisciplinary publication from Nature Publishing Group. 

Reports have shown that certain level of reactive oxygen species (ROS) could promote mitochondrial DNA (mtDNA) replication. However, whether it’s the mitochondrial ROS that stimulates mtDNA replication needs further investigation. To address this issue the researchers employed a photodynamic system to achieve controlled mitochondrial singlet oxygen generation. HeLa cells incubated with 5-aminolevulinic acid (ALA) were exposed to laser irradiation to induce singlet oxygen generation within mitochondria. Increased mtDNA copy number was detected after low dose laser irradiation in ALA-treated cells. The stimulated mtDNA replication was directly linked to mitochondrial singlet oxygen generation, as verified by specific ROS scavenger (figure 1). MtDNA control region modifications were induced by mitochondrial singlet generation (figure 2). In summary, the researchers provide a controllable way to induce mtDNA replication in vitro, which may help to elucidate the role of ROS in mtDNA genetics. In addition, the independent replication of mtDNA triggered by mitochondrial singlet oxygen indicated the semi-autonomous feature of mitochondria. 

This work was supported by grants from the Key Program of National Natural Science Foundation of China (U1432248), National Natural Science Foundation of China (No.10835011; No.11205219), and the Western Talent Program of Chinese Academy of Sciences (Y260230XB0). 

The article can be linked as follows: http://www.nature.com/articles/srep16925 .

Figure 1. Singlet oxygen in mitochondria promotes mtDNA replication. (Image by IMP) 

Figure 2. Generation of singlet oxygen in mitochondria leads to D-loop modifications. (Image by IMP)