For mitochondrial DNA content analysis, total DNA was extracted using DNAzol Reagent (Invitrogen, CA, USA) according to the manufacturer's instructions. Mitochondrial DNA was amplified using primers specific for the mitochondrial cytochrome c oxidase subunit 2 (COX2) gene and normalized to genomic DNA by amplification of the ribosomal protein s18 (rps18) nuclear gene65.
