Oxidative stress can occur in plants and other organisms in response to environmental factors. The term “oxidative stress” encompasses all cellular damage caused by the over-accumulation of reactive oxygen species (ROS). Preventing oxidative stress can improve plant performance, making this an interesting trait for exploring environmental stress tolerance in plants. However, high-throughput measurement of oxidative stress is difficult due to the complexity of cell biology and current limitations of methods for quantifying ROS and ROS-related damage. This limits the examination of this trait at a population level.
Plant cells enlist various mechanisms for ROS prevention and scavenging, involving different organelles. Peroxisomes are well-known for their role in metabolising ROS via catalase activity. Peroxisomal abundance has been suggested as a proxy measurement for ROS-scavenging activity, based on positive associations between peroxisomal abundance and ROS levels in plants. Mitochondrial ROS production, which mostly occurs via the respiratory electron transport chain, can be mitigated by activity of the alternative pathway of respiration. Increased expression of alternative respiration components has led to improved stress tolerance in model plants.
A new, high-throughput method for quantifying peroxisome abundance was used to screen 60 Australian wheat cultivars. Intraspecific variation in peroxisomal abundance and the expression of mitochondrial alternative pathway components were observed in field-grown plants and in response to combined drought and heat stress treatments in greenhouse trials. Peroxisomal abundance and mitochondrial alternative respiration components may therefore be useful “oxidative stress” indicators, for identifying genetic markers of stress tolerance in crops.