Proline Metabolism in Plant Stress Responses

Proline is a multifunctional amino acid that accumulates in plants exposed to a wide range of abiotic and biotic stresses, including drought, salinity, extreme temperatures, soil contamination and pathogen attack. Its synthesis from glutamate is catalysed primarily by Δ¹-pyrroline-5-carboxylate synthetase (P5CS) and Δ¹-pyrroline-5-carboxylate reductase, while catabolism proceeds via proline dehydrogenase (ProDH) and Δ¹-pyrroline-5-carboxylate dehydrogenase. This coordinated biosynthesis and degradation—often referred to as the Pro–P5C cycle—contributes to cellular osmotic adjustment, redox buffering and energy provision under stress. By maintaining a favourable NADP/NADPH ratio, proline metabolism supports antioxidant defence and protects photosynthetic tissues from reactive oxygen species. Stress-induced proline accumulation also stabilises proteins and membranes, acts as a molecular chaperone and influences gene expression and hormonal signalling, notably abscisic acid-mediated pathways. Proline turnover in growing tissues supplies carbon and nitrogen for recovery after stress relief, while tissue-specific partitioning ensures meristematic regions receive metabolic support. Beyond fundamental physiology, modulating proline metabolism is emerging as a strategy to enhance crop resilience, whether through genetic manipulation of key enzymes or targeted application of exogenous proline to ameliorate soil degradation and improve water-use efficiency in agriculture.

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Proline Metabolism in Plant Stress Responses publication trend

The graph below shows the total number of articles in proline metabolism in plant stress responses across all publications each year (not limited to Nature Index journals).

Technical terms

Osmolyte: Small organic compound that helps maintain cell turgor under osmotic stress.

P5CS (Δ¹-pyrroline-5-carboxylate synthetase): Enzyme catalysing the first step of proline biosynthesis from glutamate.

ProDH (proline dehydrogenase): Mitochondrial enzyme initiating proline catabolism by oxidising proline to Δ¹-pyrroline-5-carboxylate.

NADP/NADPH ratio: Cellular measure of oxidised to reduced forms of nicotinamide adenine dinucleotide phosphate, reflecting redox balance.

Abscisic acid (ABA): Plant hormone that regulates stress responses and modulates proline synthesis and degradation.

References

1. Accumulation of Proline in Plants under Contaminated Soils—Are We on the Same Page?. Antioxidants (2023).
2. Rhamnogalacturonan lyase 1 (RGL1), as a suppressor of E3 ubiquitin ligase Arabidopsis thaliana ring zinc finger 1 (AtRZF1), is involved in dehydration response to mediate proline synthesis and pectin rhamnogalacturonan‐I composition. The Plant Journal (2024).
3. Essential Role of Tissue-Specific Proline Synthesis and Catabolism in Growth and Redox Balance at Low Water Potential. Plant Physiology (2011).
4. Contribution of Exogenous Proline to Abiotic Stresses Tolerance in Plants: A Review. International Journal of Molecular Sciences (2022).
5. Unraveling Δ1-Pyrroline-5-Carboxylate-Proline Cycle in Plants by Uncoupled Expression of Proline Oxidation Enzymes*. Journal of Biological Chemistry (2009).