Contribution of Exogenous Proline to Abiotic Stresses Tolerance in Plants: A Review

Abstract

Abiotic stresses are the major environmental factors that play a significant role in decreasing plant yield and production potential by influencing physiological, biochemical, and molecular processes. Abiotic stresses and global population growth have prompted scientists to use beneficial strategies to ensure food security. The use of organic compounds to improve tolerance to abiotic stresses has been considered for many years. For example, the application of potential external osmotic protective compounds such as proline is one of the approaches to counteract the adverse effects of abiotic stresses on plants. Proline level increases in plants in response to environmental stress. Proline accumulation is not just a signal of tension. Rather, according to research discussed in this article, this biomolecule improves plant resistance to abiotic stress by rising photosynthesis, enzymatic and non-enzymatic antioxidant activity, regulating osmolyte concentration, and sodium and potassium homeostasis. In this review, we discuss the biosynthesis, sensing, signaling, and transport of proline and its role in the development of various plant tissues, including seeds, floral components, and vegetative tissues. Further, the impacts of exogenous proline utilization under various non-living stresses such as drought, salinity, high and low temperatures, and heavy metals have been extensively studied. Numerous various studies have shown that exogenous proline can improve plant growth, yield, and stress tolerance under adverse environmental factors.

Improvement of Drought Tolerance by Exogenous Spermidine in Germinating Wheat (Triticum aestivum L.) Plants Is Accompanied with Changes in Metabolite Composition

“…Among amino acids, the role of proline in stress acclimation has been widely studied and described. It may also serve as osmoprotectant and signalling molecule inducing other protective mechanisms under various abiotic stress conditions [ 39 , 40 , 41 ].…”

MsTHI1 overexpression improves drought tolerance in transgenic alfalfa (Medicago sativa L.)

“…Consequently, ROS scavenging in transgenic plants might correlate with MsTHI1 upregulation, which triggered the thiamine metabolism and the aggregation of chlorophyll to decrease the amount of ROS. The soluble protein and free Pro are key osmotic regulators, which can raise the osmotic potential of cells and boost plant tolerance to stressful conditions (Hosseinifard et al, 2022 ). In the present research, the soluble protein level in transgenic alfalfa was mainly greater than that in WT alfalfa during control or drought settings.…”

Zinc Oxide Nanoparticles: Physiological and Biochemical Responses in Barley (Hordeum vulgare L.)

“…Under stress conditions, there is a decrease in the reserves of proline used by the plant to neutralize ROS. It is believed that proline’s protective effect is related to its ability to detoxify ROS [ 10 ], inhibit lipid peroxidation [ 41 ], and act as an osmoprotectant in the case of metal toxicity [ 42 ]. Several studies have shown that exposure to metals in micro-and nano-form has revealed changes in proline content in various plant species [ 24 , 43 , 44 ].…”

“…Since both δ-ALA and proline are synthesized from a common precursor, glutamic acid, their role as antistressors can be interchangeable in vegetation periods and various plant conditions such as salinity, drought, and oxidative stress [ 2 , 42 , 46 ]. The present study showed an increase in δ-ALA, possibly due to barley’s enzymatic changes and ROS production.…”