Mechanistic understanding of photorespiration paves the way to a new green revolution

Photorespiration is frequently considered a wasteful and inefficient process. However, mutant analysis demonstrated that photorespiration is essential for recycling of 2-phosphoglycolate in C₃ and C₄ land plants, in algae, and even in cyanobacteria operating carboxysome-based carbon (C) concentrating mechanisms. Photorespiration links photosynthetic C assimilation with other metabolic processes, such as nitrogen and sulfur assimilation, as well as C₁ metabolism, and it may contribute to balancing the redox poise between chloroplasts, peroxisomes, mitochondria and cytoplasm. The high degree of metabolic interdependencies and the pleiotropic phenotypes of photorespiratory mutants impedes the distinction between core and accessory functions. Newly developed synthetic bypasses of photorespiration, beyond holding potential for significant yield increases in C₃ crops, will enable us to differentiate between essential and accessory functions of photorespiration.