Proline Production Research Articles

Cellular ATP demand creates metabolically distinct subpopulations of mitochondria.

Mitochondria serve a crucial role in cell growth and proliferation by supporting both ATP synthesis and the production of macromolecular precursors. Whereas oxidative phosphorylation (OXPHOS) depends mainly on the oxidation of intermediates from the tricarboxylic acid cycle, the mitochondrial production of proline and ornithine relies on reductive synthesis1. How these competing metabolic pathways take place in the same organelle is not clear. Here we show that when cellular dependence on OXPHOS increases, pyrroline-5-carboxylate synthase (P5CS)-the rate-limiting enzyme in the reductive synthesis of proline and ornithine-becomes sequestered in a subset of mitochondria that lack cristae and ATP synthase. This sequestration is driven by both the intrinsic ability of P5CS to form filaments and the mitochondrial fusion and fission cycle. Disruption of mitochondrial dynamics, by impeding mitofusin-mediated fusion or dynamin-like-protein-1-mediated fission, impairs the separation of P5CS-containing mitochondria from mitochondria that are enriched in cristae and ATP synthase. Failure to segregate these metabolic pathways through mitochondrial fusion and fission results in cells either sacrificing the capacity for OXPHOS while sustaining the reductive synthesis of proline, or foregoing proline synthesis while preserving adaptive OXPHOS. These findings provide evidence of the key role of mitochondrial fission and fusion in maintaining both oxidative and reductive biosyntheses in response to changing nutrient availability and bioenergetic demand.

Isolation and Characterization of Arsenic-Tolerable Bacteria from Groundwater and Their Implementation on Rice Seedling's Shoot and Root Enhancement.

Arsenic exerts detrimental impacts on primary metabolism in plants, leading to reduced crop yield. Some arsenic-resistant plant growth-promoting bacteria (PGPB) help plants by providing some plant hormones to sustain their growth and development under arsenic stress. Here, seven different species of Bacillus were isolated from arsenic-contaminated groundwater of West Bengal, India. Those species were capable of growing in the presence of > 3.12g/L arsenate (AsV) and > 0.65g/L arsenite (AsIII) salts and also resist different heavy metals like Cu2+, Fe2+, Co2+, Zn2+, Pb2+, etc. They were susceptible to multiple groups of antibiotics like beta-lactam, aminoglycosides, etc. All species were capable of detoxifying arsenite and influenced rice seedlings' growth in the presence of arsenic salts by their capabilities likenitrogen-fixing ability, phosphate solubilization, indole 3-acetic acid (IAA), gibberellic acid (GA), proline production, etc. Most species helped enhance root and shoot lengths under arsenic stress. These primary findings suggest that those Bacillus spp. could be used as potential bio-fertilizers in arsenic-contaminated agricultural fields.

Breeding for water-logging tolerance in pigeonpea: current status and future prospects

AbstractPigeonpea is grown in semi-arid tropics where the annual precipitation ranges from 200 to 800 mm and soil orders comprising of Inceptisols, Entisols, Alfisols, Vertisols, Mixed soils, and Aridisols. During monsoons, the semi-arid tropics also receive up to 140–180 mm/day rainfall for a span of 5–10 days, highlighting the chances of waterlogging in an early vegetative stage of pigeonpea, causing 25–30% yield loss in the Indian subcontinent. Waterlogging is a state where soil reaches saturation at submergence, creating an anaerobic condition in the root zone of the plants. As a result, plant withering, leaf chlorosis, stunted growth, lowered photosynthetic rate and plant mortality is evidenced widely. In response to waterlogging, the formation of aerenchyma cells, lenticels and adventitious roots were noticed as morphological adaptations. Whereas, the production of proline, peroxidase, superoxide dismutase, ethylene and alcohol dehydrogenase (ADH) as biochemical modifications. The minimal breeding efforts for waterlogging tolerance in pigeonpea may be the reason for the susceptibility of current varieties to waterlogging stress. This review emphasized the importance of breeding for waterlogging tolerance in pigeonpea. It focused on the morphological, physiological and biochemical adaptations of a plant when subjected to waterlogging stress. It accentuated the need for a standard screening protocol for waterlogging tolerance. Breeding strategies inclusive of novel single pod descent method, marker-assisted selection and rapid generation advancement techniques are discussed in detail.

Phenylalanine, Cysteine, and Sodium Selenate Alleviate Chilling Injury in Cape Gooseberry (Physalis peruviana L.) Seedlings by Enhancing Antioxidant Activities and Membrane Stability

Low temperature is a major environmental factor that negatively affects the growth and productivity of plants, such as the tropical fruit Cape gooseberry (Physalis peruviana L.), which is susceptible to cold stress. Therefore, to investigate the effect of the amino acid L-phenylalanine (Phe), L-cysteine (Cys), or sodium selenite (Se) on enhancing antioxidant activities, experiments were conducted on the phenolic compounds, proline content, and membrane stability of Cape gooseberry seedlings under low-temperature stress. The seedlings were exposed for 48 h to a low temperature (4 °C) followed by 24 h of optimal growth conditions. In seedlings treated with Se, we found a high relative water content, good membrane integrity, low ion leakage, and hydrogen peroxide. Additionally, this treatment led to the improvement of photosynthetic pigments and antioxidant activity. The analysis of seedlings under cold stress showed that the Phe enhanced the stomatal conductance and phenol content. Furthermore, low concentrations of Cys resulted in the production of proline and flavonoids, which reduced the negative effects of environmental stress on seedlings and maintained cell membrane integrity. Overall, in this experiment, the use of Se and low concentrations of Cys had a positive effect on the amount of antioxidant compounds, which improved seedling growth under stress conditions.

Inoculation of halotolerant plant-growth-promoting bacteria improved the growth of chia (Salvia hispanica L.) in saline and nonsaline soils

Context Chia (Salvia hispanica L.), a nutrient-rich crop with potential application in different industries, is sensitive to salinity. Halotolerant plant-growth promoting bacteria could be a biotechnological strategy to increase chia’s salinity tolerance. Aims The aim of this study was to determine the morphological and physiological response of chia plants inoculated with free-living halotolerant plant-growth promoting bacteria and grown in saline soils under greenhouse conditions. Methods A total of 15 bacterial treatments were inoculated to plants potted in soils with three electrical conductivity levels: 0.5, 4, and 6 dS m−1. Mortality and morphological and physiological parameters were evaluated. The measured variables were used to calculate a relative growth index. Key results Bacterial inoculation had a positive effect on plants at 4 dS m−1. Plants inoculated with Pseudomonas sp. AN23, Kushneria sp. T3.7, and C6 (Halomonas sp. 3R12 + Micrococcus luteus SA211) exhibited the best morphological and physiological performance (51% longer shoots, up to 90% heavier roots and up to 400% higher photosynthetic rate than control plants). Moreover, plants inoculated with Kushneria sp. T3.7 and C5 (Halomonas sp. 3R12 + Pseudomonas sp. AN23) showed significant increase in stomatal conductance and transpiration rate (up to 12 times) and in proline production (up to 345 μg g−1 leaf fresh weight) with respect to control plants (8 μg g−1 leaf fresh weight) under saline conditions. Conclusions The analysed extremophilic plant-growth promoting bacteria enhanced growth and stress tolerance in chia, a salt-sensitive crop. Implications Free-living plant-growth promoting bacteria isolated from hypersaline environments have potential for bioinoculant formulation for salinity-sensitive crops.

Enhancing Soybean Growth with Phytohormone-enriched PGPR Bioinoculants and Biofertilizers in Plant Stress Physiology

Background: The present investigation aimed to evaluate the effects of plant growth-promoting rhizobacteria (PGPR) bioinoculants and their carrier-based biofertilizers on the physiology of soybean. Methods: Seeds of two soybean varieties (cv. NARC-1 and cv. William-82) were either soaked in broth cultures of two PGPR strains, Planomicrobium chinense (MF616408) and Pseudomonas putida (KX574857), containing 106 cells/mL, or coated with biofertilizers. Three biofertilizers, namely biostimulant, biozote and biofert, were used. Result: Significant increases in root and shoot weight were observed with both liquid bioinoculants and carrier-based biofertilizers compared to the control. The consortium of P. chinense and P. putida resulted in the highest proline content and superoxide dismutase (SOD) activity. Biostimulant-treated plants exhibited higher catalase (CAT) activity and phenolics content. Indole-3-acetic acid (IAA) and gibberellic acid (GA) levels were enhanced in plants treated with PGPR and biofertilizers. Specifically, P. chinense and the biostimulant significantly promoted IAA content in cv. William-82, while biozote and P. chinense treatments increased GA content in both varieties. The consortium of P. chinense and P. putida showed the lowest ABA levels. The highest IAA/ABA and GA/ABA ratios were observed in plants treated with P. chinense. Liquid bioinoculants had a more pronounced effect on plant growth than carrier-based biofertilizers, though biofertilizers had stronger residual effects on rhizosphere soil organic matter. The combined effects of phytohormones, sugar, protein and proline production and antioxidant enzyme activity influenced plant growth and development.

Variation among Blackgram (Vigna mungo L.) Genotypes for Antioxidant Defence System and Yield under High Temperature Stress

Background: Blackgram is a short duration pulse crop which is sensitive to high temperatures. Raising global temperatures are becoming a serious threat to the production of blackgram by altering biochemical processes at cellular level. Hence, the present investigation was carried out for better understanding of genotypic variability and the biochemical mechanisms governing heat stress tolerance which can help in identifying heat tolerant blackgram genotypes that can yield better under climate change scenarios. Methods: Thirty blackgram genotypes selected from temperature induction response technique were evaluated for biochemical efficiency under natural high temperature conditions during summer, 2022 and 23. Field experiment was conducted at Agricultural College Farm, Acharya N.G Ranga Agricultural University, Agricultural College, Bapatla. Biochemical and yield parameters were recorded at flowering and the data were analyzed statistically and pooled. Result: The results of the study revealed that the genotypes TBG-129, LBG-1015, PU-1804 and PU-31 recorded higher seed yield indicating their ability to withstand high temperatures by up-regulating various biochemical pathways involved in increased production of proline, carotenoids and antioxidant defense enzymes that might have scavenged the free radicals that were produced due to high temperature stress, thereby preventing lipid peroxidation. Lower seed yield was recorded in TBG-125 and LBG-1023 which might be due to oxidative damage caused by higher accumulation of free radicals and poor scavenging activity of antioxidant enzymes. Moreover, the results of correlation analysis revealed that all the biochemical traits such as proline, carotenoids and antioxidant defense enzymes showed positive association with seed yield except free radicals and malondialdehyde. The principal component analysis results revealed considerable variability among the traits accounting for 80.0%. The genotypes TBG-129, LBG-1015, PU-1804 and PU-31 can be used in breeding programmes for development of heat tolerant genotypes.

FERONIA regulates salt tolerance in Arabidopsis by controlling photorespiratory flux.

Photorespiration is an energetically costly metabolic pathway in plants that responds to environmental stresses. The molecular basis of the regulation of the photorespiratory cycle under stress conditions remains unclear. Here, we discovered that FERONIA (FER) regulates photorespiratory flow under salt stress in Arabidopsis (Arabidopsis thaliana). FER mutation results in hypersensitivity to salt stress, but disruption of ferredoxin-dependent glutamate synthase 1 (GLU1), an enzyme that participates in the photorespiratory pathway by producing glutamate, greatly suppresses fer-4 hypersensitivity to salt stress primarily due to reduced glycine yield. In contrast, disrupting mitochondrial serine hydroxymethyltransferase1 (SHM1), which is supposed to increase glycine levels by hampering the conversion of glycine to serine in the photorespiratory cycle, aggravates fer-4 hypersensitivity to salt stress. Biochemical data show that FER interacts with and phosphorylates SHM1, and this phosphorylation modulates SHM1 stability. Additionally, the production of proline and its intermediate △1-pyrroline-5-carboxylate (P5C), which are both synthesized from glutamate, also contributes to fer-4 hypersensitivity to salt stress. In conclusion, this study elucidates the functional mechanism of FER in regulating salt tolerance by modulating photorespiratory flux, which greatly broadens our understanding of how plants adapt to high salinity.

Insights into trehalose mediated physiological and biochemical mechanisms in Zea mays L. under chromium stress

BackgroundChromium (Cr) toxicity significantly threatens agricultural ecosystems worldwide, adversely affecting plant growth and development and reducing crop productivity. Trehalose, a non-reducing sugar has been identified as a mitigator of toxic effects induced by abiotic stressors such as drought, salinity, and heavy metals. The primary objective of this study was to investigate the influence of exogenously applied trehalose on maize plants exposed to Cr stress.ResultsTwo maize varieties, FH-1046 and FH-1453, were subjected to two different Cr concentrations (0.3 mM, and 0.5 mM). The results revealed significant variations in growth and biochemical parameters for both maize varieties under Cr-induced stress conditions as compared to the control group. Foliar application of trehalose at a concentration of 30 mM was administered to both maize varieties, leading to a noteworthy reduction in the detrimental effects of Cr stress. Notably, the Cr (0.5 mM) stress more adversely affected the shoot length more than 0.3mM of Cr stress. Cr stress (0.5 mM) significantly reduced the shoot length by 12.4% in FH-1046 and 24.5% in FH-1453 while Trehalose increased shoot length by 30.19% and 4.75% in FH-1046 and FH-1453 respectively. Cr stress significantly constrained growth and biochemical processes, whereas trehalose notably improved plant growth by reducing Cr uptake and minimizing oxidative stress caused by Cr. This reduction in oxidative stress was evidenced by decreased production of proline, SOD, POD, MDA, H2O2, catalase, and APX. Trehalose also enhanced photosynthetic activities under Cr stress, as indicated by increased values of chlorophyll a, b, and carotenoids. Furthermore, the ameliorative potential of trehalose was demonstrated by increased contents of proteins and carbohydrates and a decrease in Cr uptake.ConclusionsThe study demonstrates that trehalose application substantially improved growth and enhanced photosynthetic activities in both maize varieties. Trehalose (30 mM) significantly increased the plant biomass, reduced ROS production and enhanced resilience to Cr stress even at 0.5 mM.

Effects of Phosphorus-Mediated Alleviation of Salt Stress on Cotton Genotypes: Biochemical Responses and Growth Adaptations

Salinity stress can significantly impact productivity in agricultural area with limited water re-sources. Our study focused on how plants under salt stress respond to phosphorus availability in terms of growth and biochemical reactions in cotton genotypes. Two cotton genotypes with different P efficiencies (SK39 and JM21) were used in a hydroponic experiment with 300 mM NaCl and three P treatments (10, 20, and 30 mM). Salinity stress decreases root growth, shoot growth, biomass production, and chlorophyll content, according to the experimental findings. In treated plants, it also increased the levels of oxidative stress. However, this effect was alleviated by phosphorus therapy, which controlled the production of proline, total soluble sugars, and hydrogen peroxide (H2O2). Interestingly, salt-sensitive JM21 responded to phosphorus supplementation more favorably than salt-tolerant SK39. Our research emphasizes the critical role that phosphorus especially P20 plays increasing the salinity stress sensitivity of cotton plants and offers insightful in-formation on the mechanisms underlying the role of phosphorus in reducing salinity stress effects. This study also revealed interspecific variability in cotton genotypes and characteristics, primarily represented by attributes related to cotton growth and morphological indicators such as dry matter biomass.

Mitigating drought-induced oxidative stress in wheat (Triticum aestivum L.) through foliar application of sulfhydryl thiourea

Drought stress is a major abiotic stress affecting the performance of wheat (Triticum aestivum L.). The current study evaluated the effects of drought on wheat phenology, physiology, and biochemistry; and assessed the effectiveness of foliar-applied sulfhydryl thiourea to mitigate drought-induced oxidative stress. The treatments were: wheat varieties; V1 = Punjab-2011, V2 = Galaxy-2013, V3 = Ujala-2016, and V4 = Anaaj-2017, drought stress; D1 = control (80% field capacity [FC]) and D2 = drought stress (40% FC), at the reproductive stage, and sulfhydryl thiourea (S) applications; S0 = control-no thiourea and S1 = foliar thiourea application @ 500 mg L−1. Results of this study indicated that growth parameters, including height, dry weight, leaf area index (LAI), leaf area duration (LAD), crop growth rate (CGR), net assimilation rate (NAR) were decreased under drought stress-40% FC, as compared to control-80% FC. Drought stress reduced the photosynthetic efficiency, water potential, transpiration rates, stomatal conductances, and relative water contents by 18, 17, 26, 29, and 55% in wheat varieties as compared to control. In addition, foliar chlorophyll a, and b contents were also lowered under drought stress in all wheat varieties due to an increase in malondialdehyde and electrolyte leakage. Interestingly, thiourea applications restored wheat growth and yield attributes by improving the production and activities of proline, antioxidants, and osmolytes under normal and drought stress as compared to control. Thiourea applications improved the osmolyte defense in wheat varieties as peroxidase, superoxide dismutase, catalase, proline, glycine betaine, and total phenolic were increased by 13, 20, 12, 17, 23, and 52%; while reducing the electrolyte leakage and malondialdehyde content by 49 and 32% as compared to control. Among the wheat varieties, Anaaj-2017 showed better resilience towards drought stress and also gave better response towards thiourea application based on morpho-physiological, biochemical, and yield attributes as compared to Punjab-2011, Galaxy-2013, and Ujala-2016. Eta-square values showed that thiourea applications, drought stress, and wheat varieties were key contributors to most of the parameters measured. In conclusion, the sulfhydryl thiourea applications improved the morpho-physiology, biochemical, and yield attributes of wheat varieties, thereby mitigating the adverse effects of drought. Moving forward, detailed studies pertaining to the molecular and genetic mechanisms under sulfhydryl thiourea-induced drought stress tolerance are warranted.

Exogenous proline suppresses endogenous proline and proline-production genes but improves the salinity tolerance capacity of salt-sensitive rice by stimulating antioxidant mechanisms and photosynthesis

Salinity is a critical environmental stress factor that significantly reduces crop productivity and yield. A mutant B-type response regulator gene (hst1) has been shown to promote salinity tolerance in the YNU genotype. Previous studies on the hst1 gene showed a higher proline production capacity under salt stress. Using almost identical genetic backgrounded salt-tolerant (YNU) and salt-sensitive (Sister line) rice genotypes, we tested the function of proline in the hst1 gene salinity-tolerance mechanism by applying exogenous proline under control and salt-stress conditions. Morpho-physiological, biochemical, and molecular analysis of ST and SS plants was performed to clarify the salinity tolerance mechanism mediated by the exogenous proline. The ST and SS genotypes accumulated exogenous proline, and the ST genotype has higher proline levels than the SS genotype. However, exogenous proline improved salt tolerance only in the SS genotype. Exogenous proline promotes plant and root growth by stimulating photosynthetic pigments and photosynthesis. The exogenous proline has a reductive effect on MDA, and H2O2 protects plants against ROS. Interestingly, exogenous proline lowers Na+ and raises K+ accumulations under salt stress. In the SS genotype, exogenous proline increases the activity of antioxidant enzymes (SOD, CAT, and APX) to protect against salinity-induced damage. The exogenous proline application down-regulates proline-synthesis genes (OsP5CS1 and OsP5CR) and up-regulates proline-degradation genes. Also, exogenous proline increases the expression of the OsSalT and OsGRAS29 genes, improving salinity tolerance in the SS genotype. Our study has demonstrated that proline plays a significant role in conferring salt tolerance with the salinity-tolerance-related hst1 mechanisms.

The biochemical properties of Satureja species affected by micronutrients, genotype, and locations in drought stress conditions

Medicinal plants, as important sources of secondary metabolites, are used for treating different diseases. It is accordingly pertinent to find methods, which may improve their growth and quality in different conditions including variable stresses. It was hypothesized micronutrients use and suitable genotypes may improve Satureja growth and quality in drought stress conditions. The objective of this study was to investigate the effects of drought stress (irrigating plants each 3 (A1), 6 (A2) and 9 days (A3)), micronutrients (Mn and Cu at 0 (M1), 20 (M2) and 40 mgL−1 (M3)), and field location (Isfahan (F1) and Golpayegan (cooler) (F2), Isfahan province, Iran) on the biochemical properties of different Satureja species including S. bakhtiarica, S. khuzestanica and S. mutica. The experimental treatments significantly affected the measured parameters including nodule number, essential oil, antioxidant activity, proline, Mn and Cu contents, and relative water content. Although Cu and Mn, enhanced plant biochemical properties, especially in M2, in some cases, the two micronutrients, unfavorably affected plant properties in M3. The responses of genotypes were different in the two research fields and S. bakhtiarica performed better in F2. The highest essential oil was resulted by A2. The two micronutrients improved plant responses in drought stress by increasing nodule number (148 %), and essential oil yield (143 %) and decreasing plant relative water content and conserving plant water. The use of Mn and Cu is recommendable for planting Satureja species in drought stress conditions, as the two nutrients may enhance plant tolerance by increasing proline production and antioxidant activities.

Multi-omics analysis provides insight into the genetic basis of proline-derived milk microbiota in buffalo

Understanding the intricate relationship between genetics, metabolites, and microbiota is paramount for unraveling the complexities that define buffalo milk composition. In this study, we employed a multi-omics approach to dissect the genetic and metabolic determinants of buffalo milk traits. Metabolomics analysis of 100 buffalo milk samples revealed a rich profile of 446 metabolites, with a particular emphasis on those associated with amino acid biosynthesis. Metabolite-based Genome-Wide Association Studies (mGWAS) uncovered 13 significant genetic variants, with a pronounced focus on l-Proline. Notably, single nucleotide polymorphisms (SNPs) within the ATG16L1 gene implicated its role in proline production. Concurrently, an in-depth exploration of milk microbiota dynamics highlighted marked differences between buffaloes with high and low proline groups. High proline abundance correlated with increased microbial diversity, dominated by Firmicutes and Proteobacteria. Distinct genera, such as Acinetobacter and Corynebacterium, characterized low and high proline groups, respectively. Functional changes in milk microbiota, especially in amino acid biosynthesis pathways, underscored proline's pivotal role in shaping microbial functions. Correlations between milk microbiota abundance and proline levels emphasized the intricate relationship between host physiology and microbial composition. These findings not only advance our understanding of the genetic basis of metabolic traits in buffalo milk but also present potential biomarkers for targeted breeding strategies. This integrated approach provides a nuanced perspective on milk composition, offering implications for dairy quality and nutritional enhancement.

Effect of Salinity Stress on the Morphological and Physiological Characteristics of Peppermint under Greenhouse Condition

Peppermint is a rich source of valuable compounds with therapeutic, coloring, preservative and other uses for humans. Peppermint is used in food, perfumery and medicine all over the world. Higher plants experience salt stress due to an excessive buildup of sodium chloride; salinity impacts plants through osmotic stress and toxicity. Salinity impacts every major activity in plants, including growth, photosynthesis, lipid metabolism, protein synthesis, energy production, and germination through biomass and seed formation. The experiment was carried out in the research farm of agriculture faculty of Lorestan University, Iran. The aim of the current research was to examine the effect of different levels of salinity (0, 50 and 100 mM) on the morphological and physiological characteristics of peppermint in the greenhouse. The result showed that salinity stress at 50 and 100 millimole (mM), decreased plant height (11.76%, 23.53%), number of leaves (25.11%, 33.92%), leaf surface (24.76%, 56.37%), crown diameter (14.15%, 25.47%), root length (20.61%, 31.58%), leaf fresh weight (14.47%, 30.47%), leaf dry weight (1.16%, 12.69%), fresh weight of stem (10.78%, 21.11%), dry weight of stem (16.32%, 37.76%), chlorophyll a (46.08% and 61.09%), Chlorophyll b (32.48% and 41.65%), total chlorophyll (40.84% and 53.59%) and carotenoid (34.67% and 67.02%) compared to the control conditions respectively. Hence, increase in salinity concentration at 50 and 100 mM, increased the amount of malondialdehyde (MDA) (37.06% and 73.63%), leaf proline (301.50% and 382.09%) and essential oil (100.40% and 80.32% compared to control. The results of this study showed that, the salinity stress had a significant effect on the morphological, physiological and biochemical characteristics of peppermint. The results showed that, increases in the salinity stress, significantly increased the amount of electrolyte leakage, production of essential oil, malondialdehyde and proline. Moreover, increase salinity levels in irrigation water, caused reduction in growth characteristics of peppermint. It is to be concluded that, Peppermint is a semi-salt resistant plant, cultivation of peppermint in the medium saline soil is recommended.

Maize multi-omics reveal leaf water status controlling of differential transcriptomes, proteomes and hormones as mechanisms of age-dependent osmotic stress response in leaves.

Drought-induced osmotic stress severely affects the growth and yield of maize. However, the mechanisms underlying the different responses of young and old maize leaves to osmotic stress remain unclear. To gain a systematic understanding of age-related stress responses, we compared osmotic-stress-induced changes in maize leaves of different ages using multi-omics approaches. After short-term osmotic stress, old leaves suffered more severe water deficits than young leaves. The adjustments of transcriptomes, proteomes, and hormones in response to osmotic stress were more dynamic in old leaves. Metabolic activities, stress signaling pathways, and hormones (especially abscisic acid) responded to osmotic stress in an age-dependent manner. We identified multiple functional clusters of genes and proteins with potential roles in stress adaptation. Old leaves significantly accumulated stress proteins such as dehydrin, aquaporin, and chaperones to cope with osmotic stress, accompanied by senescence-like cellular events, whereas young leaves exhibited an effective water conservation strategy mainly by hydrolyzing transitory starch and increasing proline production. The stress responses of individual leaves are primarily determined by their intracellular water status, resulting in differential transcriptomes, proteomes, and hormones. This study extends our understanding of the mechanisms underlying plant responses to osmotic stress.

Genetic engineering of drought- and salt-tolerant tomato via Δ1-pyrroline-5-carboxylate reductase S-nitrosylation.

Drought and soil salinization substantially impact agriculture. While proline's role in enhancing stress tolerance is known, the exact molecular mechanism by which plants process stress signals and control proline synthesis under stress is still not fully understood. In tomato (Solanum lycopersicum L.), drought and salt stress stimulate nitric oxide (NO) production, which boosts proline synthesis by activating Δ1-pyrroline-5-carboxylate synthetase (SlP5CS) and Δ1-pyrroline-5-carboxylate reductase (SlP5CR) genes and the P5CR enzyme. The crucial factor is stress-triggered NO production, which regulates the S-nitrosylation of SlP5CR at Cys-5, thereby increasing its NAD(P)H affinity and enzymatic activity. S-nitrosylation of SlP5CR enables tomato plants to better adapt to changing NAD(P)H levels, boosting both SlP5CR activity and proline synthesis during stress. By comparing tomato lines genetically modified to express different forms of SlP5CR, including a variant mimicking S-nitrosylation (SlP5CRC5W), we found that SlP5CRC5W plants show superior growth and stress tolerance. This is attributed to better P5CR activity, proline production, water use efficiency, reactive oxygen species scavenging, and sodium excretion. Overall, this study demonstrates that tomato engineered to mimic S-nitrosylated SlP5CR exhibits enhanced growth and yield under drought and salt stress conditions, highlighting a promising approach for stress-tolerant tomato cultivation.

Mitigating Salinity Stress in Pomegranate: Effects of Pseudomonas fluorescens and Glomus mosseae on Stress Responses of Red Angel and Wonderful Cultivars

Salinity stress is a major challenge in modern pomegranate orchards. The application of biofertilizers is a promising strategy to mitigate the adverse effects of salinity stress and enhance the performance in pomegranates. This experiment was conducted in 2021 to investigate the effects of salinity stress (control, 4, and 8 dS/m) and inoculation with Pseudomonas fluorescens and Glomus mosseae, either individually or in combination (Pf+Gm), on Red Angel and Wonderful pomegranate cultivars. The results revealed a significant difference in the percentage of symbiosis and colonization among the biofertilizer treatments. Pf+Gm exhibited the highest percentages of symbiosis and colonization, followed by P. fluorescens. While salinity levels did not significantly affect symbiosis percentage, they had a detrimental effect on colonization percentage. Furthermore, biofertilizer treatments significantly increased leaf density, stem growth, total chlorophyll, and total anthocyanin, while reducing ion leakage and salinity damage index. In comparison to the non-inoculated control, the Pf+Gm treatment resulted in a 53.2 % decrease in ion leakage for the Red Angel cultivar and a 39.9 % decrease for the Wonderful cultivar. Salinity had a significant effect on proline production, with the Red Angel cultivar exhibiting the highest proline content (2.09 µmol/g) in response to salinity stress of 8 ds/m. However, biofertilizer treatments increased proline content in both cultivars. In Red Angel, the Pf+Gm treatment resulted in the highest proline production in the leaves (5.82 µmol/g), which was 123 % higher than that of the non-inoculated control. Additionally, the transpiration rate decreased with increasing salinity levels, and biofertilizer treatments had varying effects on photosynthetic gas exchange and electron transport rate. The interaction effect of biofertilizer treatments and salinity on CO2 absorption was highly significant, with Pf+Gm treatment exhibiting the highest absorption (8.51 and 8.61 µmol/m2/s in Red Angel and Wonderful, respectively). These findings suggest that applied biofertilizer treatments, especially Pf+Gm, can be an effective strategy for alleviating the negative effects of salinity stress on pomegranate cultivation.

Tracking interactions between TAMs and CAFs mediated by arginase‐induced proline production during immune evasion of HCC

AbstractSynergistic changes between tumor‐associated macrophages (TAMs) and cancer‐associated fibroblasts (CAFs) aggravated immune evasion of hepatocellular carcinoma (HCC), however, the underlying molecular mechanisms remain elusive. Their continuous and dynamic interactions are subject to bioactive molecule changes. A real‐time and in situ monitoring method suitable for in vivo research of these processes would be indispensable but is scarce. In this study, a dual imaging strategy that tracing the TAMs and CAFs simultaneously was developed using a new arginase‐specific probe and established CAFs‐specific probe. The emerging roles of arginase in mediating CAFs activation in mice were explored. Results showed arginase up‐regulation in TAMs, followed by proline increase. Subsequently, proline produced by TAMs initiated the activation of CAFs. Through the JAK‐STAT signaling, CAFs up‐regulated the PD‐L1 and CTLA‐4, ultimately promoting immune evasion of HCC. This study revealed a new mechanism by which TAMs and CAFs collaborate in immune evasion, providing new targets for HCC immunotherapy.

NADK-mediated proline synthesis enhances high-salinity tolerance in the razor clam

Euryhaline organisms can accumulate organic osmolytes to maintain osmotic balance between their internal and external environments. Proline is a pivotal organic small molecule and plays an important role in osmoregulation that enables marine shellfish to tolerate high-salinity conditions. During high-salinity challenge, NAD kinase (NADK) is involved in de novo synthesis of NADP(H) in living organisms, which serves as a reducing agent for the biosynthetic reactions. However, the role of shellfish NADK in proline biosynthesis remains elusive. In this study, we show the modulation of NADK on proline synthesis in the razor clam (Sinonovacula constricta) in response to osmotic stress. Under acute hypersaline conditions, gill tissues exhibited a significant increase in the expression of ScNADK. To elucidate the role of ScNADK in proline biosynthesis, we performed dsRNA interference in the expression of ScNADK in gill tissues to assess proline content and the expression levels of key enzyme genes involved in proline biosynthesis. The results indicate that the knock-down of ScNADK led to a significant decrease in proline content (P<0.01), as well as the expression levels of two proline synthetase genes P5CS and P5CR involved in the glutamate pathway. Razor clams preferred to use ornithine as substrate for proline synthesis when the glutamate pathway is blocked. Exogenous administration of proline greatly improved cell viability and mitigated cell apoptosis in gills. In conclusion, our results demonstrate the important role of ScNADK in augmenting proline production under high-salinity stress, by which the razor clam is able to accommodate salinity variations in the ecological niche.