Redox regulation in C₃ and C₄ plants during climate change and its implications on food security

Achieving food security and sustainable food production is a major challenge for plant scientists. To accomplish this, the global food production needs not only to be remarkably boosted, but it has to be achieved under harsh environmental conditions. Moreover, the climate change scenarios estimate an enhanced pressure on crop yields in the upcoming decades. C-4 photosynthesis is highly promising to meet these challenges to global food production. Under current CO2 levels, C-4 photosynthesis is more efficient than C-3 photosynthesis, but more data is needed to map out its response under elevated CO2 (eCO(2)) conditions. Growing evidence also suggests that C-4 photosynthesis could be more efficient in water use under eCO(2). Production of reactive oxygen species (ROS) is an inevitable consequence of oxygenic photosynthesis and is also one of the first responses to environmental stresses. C-3 and C-4 plants have different ROS profiles, mainly because of reduced photorespiration in the latter. Moreover, the effects of eCO(2) on C-3 and especially C-4 plants remain poorly understood. Since C-3 and C-4 plants have different ROS production patterns, it is likely that ROS signalling and downstream effects on growth and development differ between C-3 and C-4 plants, which may result in different response to eCO(2). This would also be reflected in reproductive success and crop yields. Here we evaluate the recent literature on C-3 and C-4 plant responses to climate change conditions from the abiotic stress tolerance and food security perspectives, with redox connections. Current body of knowledge suggests engineering C-4 photosynthesis into major crops to be a viable way to increase yield, but such attempts have failed because of a lack of basic knowledge in this area. Therefore, this article also aims to fill this gap from the redox perspective.