Regulation of Proline Accumulation and Its Molecular and Physiological Functions in Stress Defence

Forlani, Giuseppe; Trovato, Maurizio; Funck, Dietmar; Signorelli, Santiago

doi:10.1007/978-3-030-27423-8_3

Cited by 71 publications

(62 citation statements)

References 115 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Overall, NaCl accumulation, pigment loss and inhibition of photosynthetic electron transport were not significantly different between wildtype plants and p5cs1-4 mutants, despite the strongly reduced proline accumulation in p5cs1-4 mutants ( Figures 7 , 8 , Supplementary Figure S6 ). Notably, the reduced proline content did not result in an altered osmolality of crude leaf extracts from p5cs1-4 mutants ( Figure 7B ), supporting previous estimations that the function of proline accumulation cannot be primarily the osmotic adjustment during stress ( Hare and Cress, 1997 ; Forlani et al., 2019b ). However, partitioning studies indicated that the predominant accumulation of proline in the cytosol and in chloroplasts of osmotically stressed potato leaves and in salt-stressed sugar beet may account for a relevant osmotic function of proline in these compartments ( Büssis and Heineke, 1998 ; Hossain et al., 2017 ).…”

Section: Discussionsupporting

confidence: 88%

“…Stress-induced alterations of protein biosynthesis and degradation rates may also affect free amino acid concentrations, but are not expected to cause a specific increase in proline (Hildebrandt, 2018). High concentrations of proline can stabilize proteins and membranes, and it has been suggested that proline accumulation stimulates the antioxidant defense system (Forlani et al, 2019b;Zouari et al, 2019). Direct contributions of proline to radical scavenging and osmotic adjustment have also been proposed but the evidence is controversial (Forlani et al, 2019a).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Differential Contribution of P5CS Isoforms to Stress Tolerance in Arabidopsis

et al. 2020

Self Cite

View full text Add to dashboard Cite

Proline accumulation is a widespread response of plants to salt stress as well as drought and cold stress. In most plant species, two isoforms of pyrroline-5-carboxylate synthetase (P5CS) catalyze the first step in proline biosynthesis from glutamate. In Arabidopsis, these isoforms differ in their spatial and temporal expression patterns, suggesting subfunctionalization. P5CS1 has been identified as the major contributor to stress-induced proline accumulation, whereas P5CS2 has been considered important for embryo development and growth. In contrast to previous results, our analysis of P5CS1-and P5CS2-GFP fusion proteins indicates that both enzymes were exclusively localized in the cytosol. The comparison of the susceptibility of p5cs1 and p5cs2 mutants to infection with Pseudomonas syringae and salt stress provided novel information on the contribution of the two P5CS isoforms to proline accumulation and stress tolerance. In agreement with previous studies, salt-stressed p5cs1 mutants accumulated very little proline, indicating that P5CS1 contributed more to stress-induced proline accumulation, whereas its impact on stress tolerance was rather weak. Germination and establishment of p5cs2 mutants were impaired under ambient conditions, further supporting that P5CS2 is most important for growth and development, whereas its contribution to stress-induced proline accumulation was smaller than that of P5CS1. In contrast to p5cs1 mutants or wildtype plants, p5cs2 mutants were only weakly affected by sudden exposure to a high NaCl concentration. These findings show that proline content, which was intermediate in leaves of p5cs2 mutants, was not directly correlated with stress tolerance in our experiments. In rosettes of NaCl-exposed p5cs2 mutants, nearly no accumulation of Na + was observed, and the plants showed neither chlorosis nor reduction of photosynthesis. Based on these data, we suggest a function of P5CS2 or P5CS2mediated proline synthesis in regulating Na + accumulation in leaves and thereby salt stress tolerance.

show abstract

Section: Discussionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Differential Contribution of P5CS Isoforms to Stress Tolerance in Arabidopsis

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, during recent years increasing evidence has been reported that suggests a more faceted protective role of intracellular free proline (Sharma et al, 2011;Shinde et al, 2016;Signorelli, 2016), and even slight increases of its intracellular content, well below those required for effective osmotic compensation, were found beneficial under stress. The exact mechanisms underlying these positive effects are still a matter of debate (Forlani et al, 2019b), and some data also suggest that an increase in proline metabolic rates, more than its absolute concentration, may help the cell to counteract abiotic stress conditions (Kavi Kishor and Sreenivasulu, 2014;Forlani et al, 2019a). To allow a deeper insight in these metabolic plant responses, there would consequently be a need of methods able to reliably detect even minor variations in proline levels.…”

Section: Introductionmentioning

confidence: 99%

A Specific and Sensitive Enzymatic Assay for the Quantitation of L-Proline

Forlani

Funck

2020

Front. Plant Sci.

Self Cite

View full text Add to dashboard Cite

Because proline accumulates rapidly in response to several stress conditions such as drought and excess salt, increased intracellular levels of free proline are considered a hallmark of adaptive reactions in plants, particularly in response to water stress. Proline quantitation is easily achievable by reaction with ninhydrin, since under acidic conditions peculiar red or yellow reaction products form with this unique cyclic amino acid. However, little attention has been paid to date to cross-reaction of ninhydrin with other amino acids at high levels, or with structurally related compounds that may also be present at significant concentrations in plant tissues, possibly leading to proline overestimation. In vitro at high pH values, δ 1-pyrroline-5-carboxylate reductase, the enzyme catalyzing the second and last step in proline synthesis from glutamate, was early found to catalyze the reverse oxidation of proline with the concomitant reduction of NAD(P) + to NAD(P)H. Here we characterized this reverse reaction using recombinant enzymes from Arabidopsis thaliana and Oryza sativa, and demonstrated its utility for the specific quantification of L-proline. By optimizing the reaction conditions, fast, easy, and reproducible measurement of L-proline concentration was achieved, with similar sensitivity but higher specificity than the commonly used ninhydrin methods.

show abstract

Section: Introductionmentioning

confidence: 99%

“…Many prokaryotes and eukaryotes accumulate free proline as a compatible solute in response to abiotic or biotic stress ( Forlani et al, 2019 ; Trovato et al, 2019 ). Therefore, in order to improve crop performance under stress conditions, a lot of research has been dedicated to understand the molecular basis of proline accumulation and the role of this amino acid in plant acclimation and stress tolerance ( Szabados and Savoure, 2010 ; Forlani et al, 2019 ; El Moukhtari et al, 2020 ). Multi-level analyses and flux modeling demonstrated that different plant species rely on different regulatory mechanisms of either transcriptional regulation or modulation of enzyme activities to shift the balance between proline biosynthesis, consumption, and degradation toward proline accumulation ( AbdElgawad et al, 2015 ; Hildebrandt, 2018 ; Dellero et al, 2020 ).…”

Section: Introductionmentioning

confidence: 99%

Appropriate Activity Assays Are Crucial for the Specific Determination of Proline Dehydrogenase and Pyrroline-5-Carboxylate Reductase Activities

et al. 2020

Self Cite

View full text Add to dashboard Cite

Accumulation of proline is a widespread plant response to a broad range of environmental stress conditions including salt and osmotic stress. Proline accumulation is achieved mainly by upregulation of proline biosynthesis in the cytosol and by inhibition of proline degradation in mitochondria. Changes in gene expression or activity levels of the two enzymes catalyzing the first reactions in these two pathways, namely pyrroline-5-carboxylate (P5C) synthetase and proline dehydrogenase (ProDH), are often used to assess the stress response of plants. The difficulty to isolate ProDH in active form has led several researchers to erroneously report proline-dependent NAD+ reduction at pH 10 as ProDH activity. We demonstrate that this activity is due to P5C reductase (P5CR), the second and last enzyme in proline biosynthesis, which works in the reverse direction at unphysiologically high pH. ProDH does not use NAD+ as electron acceptor but can be assayed with the artificial electron acceptor 2,6-dichlorophenolindophenol (DCPIP) after detergent-mediated solubilization or enrichment of mitochondria. Seemingly counter-intuitive results from previous publications can be explained in this way and our data highlight the importance of appropriate and specific assays for the detection of ProDH and P5CR activities in crude plant extracts.

show abstract

Regulation of Proline Accumulation and Its Molecular and Physiological Functions in Stress Defence

Cited by 71 publications

References 115 publications

Differential Contribution of P5CS Isoforms to Stress Tolerance in Arabidopsis

Differential Contribution of P5CS Isoforms to Stress Tolerance in Arabidopsis

A Specific and Sensitive Enzymatic Assay for the Quantitation of L-Proline

Appropriate Activity Assays Are Crucial for the Specific Determination of Proline Dehydrogenase and Pyrroline-5-Carboxylate Reductase Activities

Contact Info

Product

Resources

About