Oxidative and Glycation Damage to Mitochondrial DNA and Plastid DNA during Plant Development

Abstract

Oxidative damage to plant proteins, lipids, and DNA caused by reactive oxygen species (ROS) has long been studied. The damaging effects of reactive carbonyl groups (glycation damage) to plant proteins and lipids have also been extensively studied, but only recently has glycation damage to the DNA in plant mitochondria and plastids been reported. Here, we review data on organellar DNA maintenance after damage from ROS and glycation. Our focus is maize, where tissues representing the entire range of leaf development are readily obtained, from slow-growing cells in the basal meristem, containing immature organelles with pristine DNA, to fast-growing leaf cells, containing mature organelles with highly-fragmented DNA. The relative contributions to DNA damage from oxidation and glycation are not known. However, the changing patterns of damage and damage-defense during leaf development indicate tight coordination of responses to oxidation and glycation events. Future efforts should be directed at the mechanism by which this coordination is achieved.

Keywords: AGEs; DNA repair; ROS; antioxidants; maize; mtDNA; ptDNA.

Figure 1

Damage in maize organelles during development. Cellular and organellar development in maize proceeds from the basal meristem to the fully expanded leaf blade. For light-grown maize seedlings, samples from lower 1/3 stalk (includes basal meristem), upper 2/3 stalk, and first leaf (L1) were assayed for ROS, glycation, and orgDNA damage [27,48]. Similar assays were performed for seedlings grown in light or in continuous dark using tissue from the first three leaf blades (L1, L2, and L3). Levels of antioxidants and the deglycase DJ-1 protein were higher in promitochondria and proplastids than in mature organelles. In contrast, levels of ROS and glycation products were higher in mature mitochondria and chloroplasts, where greater orgDNA damage was evident. Less ROS, glycation, and DNA damage were also found in dark-grown, etiolated leaves than in leaves grown under normal light conditions. The developmental changes from ROS and glycation damage to orgDNA result in a lower number of functional genome copies among the number typically scored as “copies” using methods such as standard qPCR [27,45,46,48].