Accumulation of Proline in Plants under Contaminated Soils—Are We on the Same Page?

Abstract

Agricultural soil degradation is occurring at unprecedented rates, not only as an indirect effect of climate change (CC) but also due to intensified agricultural practices which affect soil properties and biodiversity. Therefore, understanding the impacts of CC and soil degradation on plant physiology is crucial for the sustainable development of mitigation strategies to prevent crop productivity losses. The amino acid proline has long been recognized for playing distinct roles in plant cells undergoing osmotic stress. Due to its osmoprotectant and redox-buffering ability, a positive correlation between proline accumulation and plants’ tolerance to abiotic stress has been pointed out in numerous reviews. Indeed, proline quantification is used systematically by plant physiologists as an indicator of the degree of tolerance and a measurement of the antioxidant potential in plants under stressful conditions. Moreover, the exogenous application of proline has been shown to increase resilience to several stress factors, including those related to soil degradation such as salinity and exposure to metals and xenobiotics. However, recent data from several studies often refer to proline accumulation as a signal of stress sensitivity with no clear correlation with improved antioxidant activity or higher stress tolerance, including when proline is used exogenously as a stress reliever. Nevertheless, endogenous proline levels are strongly modified by these stresses, proving its involvement in plant responses. Hence, one main question arises—is proline augmentation always a sign of improved stress resilience? From this perspective, the present review aims to provide a more comprehensive understanding of the implications of proline accumulation in plants under abiotic stress induced by soil degradation factors, reinforcing the idea that proline quantification should not be employed as a sole indicator of stress sensitivity or resilience but rather complemented with further biochemical and physiological endpoints.

Assessment of Protein Quality and Digestibility in Plant-Based Meat Analogues

“…This can be ascribed to the adverse conditions that the plant has had to endure. Indeed, it is well-known that when subjected to biotic and/or abiotic stresses (i.e., fungi, weeds, contaminated soil), plants accumulate proline. , Proline is in fact known to have an important role in the recovery from stress in plants, acting as a signal molecule to modulate plant functions (i.e., regulating osmotic and redox balance, influencing cell proliferation or apoptosis, etc. ). , Moreover, proline is one of the main constituents of prolaminsgenerally from 6 to 12%which are gluten proteins .…”

Comparative metabolomic analysis between tomato and halophyte plants under intercropping conditions

“…Interestingly, a decrease in proline was also recorded in H +T plants (Table 6). Under salinity conditions, proline limits Na + and Cl − accumulation in cells, ensuring a proper osmotic adjustment and displaying low proline content in the absence of salt stress (Spormann et al, 2023). It can be hypothesized that the observed decrease in the Na + and Cl − levels by intercropping (Table 4) could lead to a decline in proline content in tomato plants.…”

Determination of Physiochemical Characteristics Associated with Various Degrees of Cadmium Tolerance in Barley Accessions

“…Under the presence of heavy metals, PC can directly chelate these substrates and, accordingly, reduce the toxic effects of metals on plant organs [53]. The accumulation of proline is also related to carbohydrate metabolism.…”