Proline Alleviates Abiotic Stress Induced Oxidative Stress in Plants

Oxidative stress is common in plants growing under extreme environments, such as water shortage, salinity, heavy metals, and temperature extremes. To overcome oxidative stress, plants employ various endogenous strategies, including the oxidative defense system and osmolyte accumulation. Proline (Pro), a key organic osmolyte, generally accumulates in plants under harsh environmental stress. The over-accumulation of Pro in most plants under abiotic stress has been linked to elevated activities of vital enzymes and the expression of corresponding Pro metabolism genes or inhibition in Pro catabolism. Moreover, accumulating knowledge of Pro regulation has shown that this potential osmolyte can scavenge free radicals generated by plants under various stressors. Thus, efforts are underway to enhance plant tolerance to oxidative stress either by applying exogenous Pro or transforming the genes involved in Pro metabolism. This review discusses how and to what extent Pro is involved in relieving oxidative stress to regulate plant survival under extreme environments. It also presents an overview on adopting advanced genome-editing technologies, such as CRISPR, for editing appropriate genes of Pro metabolism aiming to develop stress-resistant crop plants. This information is crucial for developing oxidative-stress-resistant crops by tailoring Pro metabolism genes to overcome the future food security challenges under the changing climate scenario.