The Biological and Agronomic Nexus Behind Protoporphyrinogen IX Oxidase (PPO)-Inhibiting Herbicide Resistance in Crops

Abstract The repeated use of a single herbicide over many years results in the emergence of resistant weeds, posing a significant danger to food security. Current attempts to prevent herbicide-resistant weeds from evolving and spreading rely mostly on the creation of genetically engineered herbicide-resistant crops and the implementation of herbicide rotation strategies with varied modes of action. In recent years, protoporphyrinogen oxidase (PPO)-inhibiting herbicides have gained popularity for weed management in fields as a result of the slow evolution of PPO-inhibitor resistance and the widespread emergence of weed resistance to acetolactate synthase-inhibitor and glyphosate. The slowly emerging resistance to PPO herbicides enables long-term weed control and ensures the efficiency of PPO inhibitors in managing herbicide-resistant weeds. Recognizing its importance for food security, this review explores innovative strategies for developing crops resistant to PPO-inhibiting herbicides. The review in particular attempts to provide a more detailed explanation of strategies including conventional tissue culture, prokaryotic, amino acid substitution, Fe-chelatase, and circadian clock-controlled gene regulation. All of which contributes to our understanding of how these strategies maintain sufficient PPO enzymatic activity while moderating the herbicide's inhibitory effects and supporting the cells’ continued growth and survival under herbicide application.