Abstract:

The activity of cytochrome c oxidase (COX) and the expression levels of mitochondrial DNA (mtDNA)-encoded
COX subunits in two peach (Prumus persica) cultivars ‘Yuhuasanhao’ and ‘Jianayan’ were determined for analyzing their
relationship with peach fruit ripening and senescence. The results showed that COX activities in the two peach cultivars
increased in the early stages of maturity (Ⅰ–Ⅲ), followed by a decrease. COX activities were higher in ‘Jianayan’ peach
fruit than in ‘Yuhua 3’ peach fruit. The expression levels of mtDNA- encoded COX subunits were higher in the early stage
than in the later stage of maturity. MtDNA-encoded COX subunits played a major role in the early maturity stage of peach
fruit and provided the energy needed for peach growth and metabolism. In the later maturity stage, the decreases in the
abundance of catalytic subunits of mtDNA-encoded COX could underlie the senescence-associated loss of enzyme activity,
which could change a component of the mitochondrial electron transport chain and underlie the senescence-related decrease
in mitochondrial respiratory activity and reactive oxygen species accumulation.

Key words: peach, mitochondria, respiration rate, cytochrome c oxidase