Hepatitis C Virus Dysregulates Polyamine and Proline Metabolism and Perturbs the Urea Cycle.

Hepatitis C virus (HCV) is an oncogenic virus that causes chronic liver disease in more than 80% of patients. During the last decade, efficient direct-acting antivirals were introduced into clinical practice. However, clearance of the virus does not reduce the risk of end-stage liver diseases to the level observed in patients who have never been infected. So, investigation of HCV pathogenesis is still warranted. Virus-induced changes in cell metabolism contribute to the development of HCV-associated liver pathologies. Here, we studied the impact of the virus on the metabolism of polyamines and proline as well as on the urea cycle, which plays a crucial role in liver function. It was found that HCV strongly suppresses the expression of arginase, a key enzyme of the urea cycle, leading to the accumulation of arginine, and up-regulates proline oxidase with a concomitant decrease in proline concentrations. The addition of exogenous proline moderately suppressed viral replication. HCV up-regulated transcription but suppressed protein levels of polyamine-metabolizing enzymes. This resulted in a decrease in polyamine content in infected cells. Finally, compounds targeting polyamine metabolism demonstrated pronounced antiviral activity, pointing to spermine and spermidine as compounds affecting HCV replication. These data expand our understanding of HCV's imprint on cell metabolism.

Mitigation of salinity stress in yarrow (Achillea millefolium L.) plants through spermidine application.

This study investigated the mitigating effects of spermidine on salinity-stressed yarrow plants (Achillea millefolium L.), an economically important medicinal crop. Plants were treated with four salinity levels (0, 30, 60, 90 mM NaCl) and three spermidine concentrations (0, 1.5, 3 µM). Salinity induced electrolyte leakage in a dose-dependent manner, increasing from 22% at 30 mM to 56% at 90 mM NaCl without spermidine. However, 1.5 µM spermidine significantly reduced leakage across salinities by 1.35-11.2% relative to untreated stressed plants. Photosynthetic pigments (chlorophyll a, b, carotenoids) also exhibited salinity- and spermidine-modulated responses. While salinity decreased chlorophyll a, both spermidine concentrations increased chlorophyll b and carotenoids under most saline conditions. Salinity and spermidine synergistically elevated osmoprotectants proline and total carbohydrates, with 3 µM spermidine augmenting proline and carbohydrates up to 14.4% and 13.1% at 90 mM NaCl, respectively. Antioxidant enzymes CAT, POD and APX displayed complex regulation influenced by treatment factors. Moreover, salinity stress and spermidine also influenced the expression of linalool and pinene synthetase genes, with the highest expression levels observed under 90 mM salt stress and the application of 3 µM spermidine. The findings provide valuable insights into the responses of yarrow plants to salinity stress and highlight the potential of spermidine in mitigating the adverse effects of salinity stress.

Elicitors directed in vitro growth and production of stevioside and other secondary metabolites in Stevia rebaudiana (Bertoni) Bertoni.

Stevia rebaudiana (stevia) is a plant in the Asteraceae that contains several biologically active compounds including the antidiabetic diterpene glycosides (e.g. stevioside, rebaudioside and dulcoside) that can serve as zero-calorie sugar alternatives. In this study, an elicitation strategy was applied using 5% polyethylene glycol (PEG), sodium chloride (NaCl; 50 and 100 mM) and gibberellic acid (2.0 and 4.0 mg/L GA3) to investigate their effect on shoot morphogenesis, and the production of phenolics, flavonoids, total soluble sugars, proline and stevioside, as well as antioxidant activity, in shoot cultures of S. rebaudiana. Herewith, the media supplemented with 2 mg/L and 4 mg/L GA3 exhibited the highest shooting response (87% and 80%). The augmentation of lower concentrations of GA3 (2 mg/L) in combination with 6-benzylaminopurine (BAP) resulted in the maximum mean shoot length (11.1 cm). The addition of 100 mM NaCl salts to the media led to the highest observed total phenolics content (TPC; 4.11 mg/g-DW compared to the control 0.52 mg/g-DW), total flavonoids content (TFC; 1.26 mg/g-DW) and polyphenolics concentration (5.39 mg/g-DW) in shoots cultured. However, the maximum antioxidant activity (81.8%) was observed in shoots raised in media treated with 50 mM NaCl. The application of 2 mg/L of GA3 resulted in the highest accumulation of proline (0.99 µg/mL) as compared to controls (0.37 µg/mL). Maximum stevioside content (71 µL/mL) was observed in cultures supplemented with 100 mM NaCl and 5% PEG, followed by the 4 mg/L GA3 treatment (70 µL/mL) as compared to control (60 µL/mL). Positive correlation was observed between GA3 and stevioside content. Notably, these two compounds are derived from a shared biochemical pathway. These results suggest that elicitation is an effective option to enhance the accumulation of steviosides and other metabolites and provides the groundwork for future industrial scale production using bioreactors.

Phenotyping revealed tolerance traits and genotypes for acidity and aluminum toxicity in European Vicia faba L.

Soil acidity is a global issue; soils with pH <4.5 are widespread in Europe. This acidity adversely affects nutrient availability to plants; pH levels <5.0 lead to aluminum (Al3+) toxicity, a significant problem that hinders root growth and nutrient uptake in faba bean (Vicia faba L.) and its symbiotic relationship with Rhizobium. However, little is known about the specific traits and tolerant genotypes among the European faba beans. This study aimed to identify response traits associated with tolerance to root zone acidity and Al3+ toxicity and potentially tolerant genotypes for future breeding efforts. Germplasm survey was conducted using 165 genotypes in a greenhouse aquaponics system. Data on the root and shoot systems were collected. Subsequently, 12 genotypes were selected for further phenotyping in peat medium, where data on physiological and morphological parameters were recorded along with biochemical responses in four selected genotypes. In the germplasm survey, about 30% of genotypes showed tolerance to acidity and approximately 10% exhibited tolerance to Al3+, while 7% showed tolerance to both. The phenotyping experiment indicated diverse morphological and physiological responses among treatments and genotypes. Acid and Al3+ increased proline concentration. Interaction between genotype and environment was observed for ascorbate peroxidase activity, malondialdehyde, and proline concentrations. Genomic markers associated with acidity and acid+Al3+-toxicity tolerances were identified using GWAS analysis. Four faba bean genotypes with varying levels of tolerance to acidity and Al3+ toxicity were identified.

Plants interfere with non-self recognition of a phytopathogenic fungus via proline accumulation to facilitate mycovirus transmission.

Non-self recognition is a fundamental aspect of life, serving as a crucial mechanism for mitigating proliferation of molecular parasites within fungal populations. However, studies investigating the potential interference of plants with fungal non-self recognition mechanisms are limited. Here, we demonstrate a pronounced increase in the efficiency of horizontal mycovirus transmission between vegetatively incompatible Sclerotinia sclerotiorum strains in planta as compared to in vitro. This increased efficiency is associated with elevated proline concentration in plants following S. sclerotiorum infection. This surge in proline levels attenuates the non-self recognition reaction among fungi by inhibition of cell death, thereby facilitating mycovirus transmission. Furthermore, our field experiments reveal that the combined deployment of hypovirulent S. sclerotiorum strains harboring hypovirulence-associated mycoviruses (HAVs) together with exogenous proline confers substantial protection to oilseed rape plants against virulent S. sclerotiorum. This unprecedented discovery illuminates a novel pathway by which plants can counteract S. sclerotiorum infection, leveraging the weakening of fungal non-self recognition and promotion of HAVs spread. These promising insights provide an avenue to explore for developing innovative biological control strategies aimed at mitigating fungal diseases in plants by enhancing the efficacy of horizontal HAV transmission.

The impact of polystyrene nanoplastics (PSNPs) on physiological and biochemical parameters of the microalgae Spirulina platensis.

Nanoplastics, as emerging pollutants, have harmful effects on living organisms and the environment, the mechanisms and extent of which remain unclear. Microalgae, as one of the most important biological groups in the food chain and sensitive environmental indicators to various pollutants, are considered a suitable option for investigating the effects of nanoplastics. In this study, the effects of polystyrene nanoplastics on the growth rate, dry weight, chlorophyll a and carotenoid levels, proline, and lipid peroxidation in the Spirulina platensis were examined. Three concentrations of 0.1, 1, and 10 mg L-1 of PSNPs were used alongside a control sample with zero concentration, with four repetitions in one-liter containers for 20 days under optimal temperature and light conditions. Various analyses, including growth rate, dry weight, proline, chlorophyll a and carotenoid levels, and lipid peroxidation, were performed. The results indicated that exposure to PSNP stress led to a significant decrease in growth rate, dry weight, and chlorophyll a and carotenoid levels compared to the control sample. Furthermore, this stress increased the levels of proline and lipid peroxidation in Spirulina platensis. Morphological analysis via microscopy supported these findings, indicating considerable environmental risks associated with PSNPs.

Comprehensive evaluation of drought tolerance of six Chinese chestnut varieties (clones) based on flavonoids and other physiological indexes.

Flavonoids are crucial secondary metabolites that possess the ability to mitigate UV damage and withstand both biotic and abiotic stresses. Therefore, it is of immense significance to investigate the flavonoid content as a pivotal indicator for a comprehensive assessment of chestnut's drought tolerance. This study aimed to determine the flavonoid content and drought tolerance-related physiological and biochemical indices of six chestnut varieties (clones) grafted trees-Qianxi 42 (QX42), Qinglong 45 (QL45), Yanshanzaofeng (YSZF), Yanzi (YZ), Yanqiu (YQ), and Yanlong (YL)-under natural drought stress. The results were used to comprehensively analyze the drought tolerance ability of these varieties. The study revealed that the ranking of drought tolerance indices in terms of their ability to reflect drought tolerance was as follows: superoxide (oxide) dismutase (SOD) activity, ascorbate peroxidase (APX) activity, flavone content, catalase (CAT) activity, proline (PRO) content, soluble sugar content, peroxidase (POD) activity, betaine content, flavonol content, hydrogen peroxide (H2O2) content, soluble protein content, superoxide ion (OFR) content, superoxide (ion OFR) production rate, malondialdehyde (MDA) content, chlorophyll content. Through principal component analysis, the contents of flavonoids and flavonols can be used as indicators for comprehensive evaluation of drought tolerance of chestnut. The comprehensive evaluation order of drought tolerance of grafted trees of 6 chestnut varieties (Clones) was: QL45 > QX42 > YQ > YZ > YSZF > YL.

Amyloidogenic regions in beta-strands II and III modulate the aggregation and toxicity of SOD1 in living cells.

Mutations in the protein superoxide dismutase-1 (SOD1) promote its misfolding and aggregation, ultimately causing familial forms of the debilitating neurodegenerative disease amyotrophic lateral sclerosis (ALS). Currently, over 220 (mostly missense) ALS-causing mutations in the SOD1 protein have been identified, indicating that common structural features are responsible for aggregation and toxicity. Using in silico tools, we predicted amyloidogenic regions in the ALS-associated SOD1-G85R mutant, finding seven regions throughout the structure. Introduction of proline residues into ß-strands II (I18P) or III (I35P) reduced the aggregation propensity and toxicity of SOD1-G85R in cells, significantly more so than proline mutations in other amyloidogenic regions. The I18P and I35P mutations also reduced the capability of SOD1-G85R to template onto previously formed non-proline mutant SOD1 aggregates as measured by fluorescence recovery after photobleaching. Finally, we found that, while the I18P and I35P mutants are less structurally stable than SOD1-G85R, the proline mutants are less aggregation-prone during proteasome inhibition, and less toxic to cells overall. Our research highlights the importance of a previously underappreciated SOD1 amyloidogenic region in ß-strand II (15QGIINF20) to the aggregation and toxicity of SOD1 in ALS mutants, and suggests that ß-strands II and III may be good targets for the development of SOD1-associated ALS therapies.

Growth and antioxidant responses to water stress in eggplant MAGIC population parents, F1 hybrids and a subset of recombinant inbred lines.

BACKGROUND: The generation of new eggplant (Solanum melongena L.) cultivars with drought tolerance is a main challenge in the current context of climate change. In this study, the eight parents (seven of S. melongena and one of the wild relative S. incanum L.) of the first eggplant MAGIC (Multiparent Advanced Generation Intercrossing) population, together with four F1 hybrids amongst them, five S5 MAGIC recombinant inbred lines selected for their genetic diversity, and one commercial hybrid were evaluated in young plant stage under water stress conditions (30% field capacity; FC) and control conditions (100% FC). After a 21-day treatment period, growth and biomass traits, photosynthetic pigments, oxidative stress markers, antioxidant compounds, and proline content were evaluated. RESULTS: Significant effects (p < 0.05) were observed for genotype, water treatments and their interaction in most of the traits analyzed. The eight MAGIC population parental genotypes displayed a wide variation in their responses to water stress, with some of them exhibiting enhanced root development and reduced foliar biomass. The commercial hybrid had greater aerial growth compared to root growth. The four F1 hybrids among MAGIC parents differed in their performance, with some having significant positive or negative heterosis in several traits. The subset of five MAGIC lines displayed a wide diversity in their response to water stress. CONCLUSION: The results show that a large diversity for tolerance to drought is available among the eggplant MAGIC materials, which can contribute to developing drought-tolerant eggplant cultivars.

Dynamic Arabidopsis P5CS filament facilitates substrate channelling.

In plants, the rapid accumulation of proline is a common response to combat abiotic stress1-7. Delta-1-pyrroline-5-carboxylate synthase (P5CS) is a rate-limiting enzyme in proline synthesis, catalysing the initial two-step conversion from glutamate to proline8. Here we determine the first structure of plant P5CS. Our results show that Arabidopsis thaliana P5CS1 (AtP5CS1) and P5CS2 (AtP5CS2) can form enzymatic filaments in a substrate-sensitive manner. The destruction of AtP5CS filaments by mutagenesis leads to a significant reduction in enzymatic activity. Furthermore, separate activity tests on two domains reveal that filament-based substrate channelling is essential for maintaining the high catalytic efficiency of AtP5CS. Our study demonstrates the unique mechanism for the efficient catalysis of AtP5CS, shedding light on the intricate mechanisms underlying plant proline metabolism and stress response.

Introgression of Δ1-pyrroline-5-carboxylate synthetase (PgP5CS) confers enhanced resistance to abiotic stresses in transgenic tobacco.

Δ1-pyrroline-5-carboxylate synthetase (P5CS) is one of the key regulatory enzymes involved in the proline biosynthetic pathway. Proline acts as an osmoprotectant, molecular chaperone, antioxidant, and regulator of redox homeostasis. The accumulation of proline during stress is believed to confer tolerance in plants. In this study, we cloned the complete CDS of the P5CS from pearl millet (Pennisetum glaucum (L.) R.Br. and transformed into tobacco. Three transgenic tobacco plants with single-copy insertion were analyzed for drought and heat stress tolerance. No difference was observed between transgenic and wild-type (WT) plants when both were grown in normal conditions. However, under heat and drought, transgenic plants have been found to have higher chlorophyll, relative water, and proline content, and lower malondialdehyde (MDA) levels than WT plants. The photosynthetic parameters (stomatal conductance, intracellular CO2 concentration, and transpiration rate) were also observed to be high in transgenic plants under abiotic stress conditions. qRT-PCR analysis revealed that the expression of the transgene in drought and heat conditions was 2-10 and 2-7.5 fold higher than in normal conditions, respectively. Surprisingly, only P5CS was increased under heat stress conditions, indicating the possibility of feedback inhibition. Our results demonstrate the positive role of PgP5CS in enhancing abiotic stress tolerance in tobacco, suggesting its possible use to increase abiotic stress-tolerance in crops for sustained yield under adverse climatic conditions.

Proline inhibits postharvest physiological deterioration of cassava by improving antioxidant capacity.

Cassava (Manihot esculenta Crantz), a crucial global tuber crop, encounters significant economic losses attributed to postharvest physiological deterioration (PPD). The PPD phenomenon in cassava is closely related to the accumulation of reactive oxygen species (ROS), and amino acids play a pivotal role in regulating signaling pathways and eliminating ROS. In this study, the storage performance of eight cassava varieties were conducted. Cassava cultivar SC5 showed the best storage performance among the eight cassava varieties, but the edible cassava cultivar SC9 performed much worse. Comparative analysis of free amino acids was conducted in eight cassava varieties, revealing changes in proline, aspartic acid, histidine, glutamic acid, threonine, and serine. Exogenous supplementation of these six amino acids was performed to inhibit PPD of SC9. Proline was confirmed as the key amino acid for inhibiting PPD. Treatment with optimal exogenous proline of 5 g/L resulted in a 17.9% decrease in the deterioration rate compared to untreated cassava. Accompanied by a decrease in H2O2 content and an increase in catalase, superoxide dismutase and ascorbate peroxidase activity. Proline treatment proved to be an effective approach to alleviate cell oxidative damage, inhibit PPD in cassava, and prolong shelf life.

Structural basis for the distinct roles of non-conserved Pro116 and conserved Tyr124 of BCH domain of yeast p50RhoGAP.

p50RhoGAP is a key protein that interacts with and downregulates the small GTPase RhoA. p50RhoGAP is a multifunctional protein containing the BNIP-2 and Cdc42GAP Homology (BCH) domain that facilitates protein-protein interactions and lipid binding and the GAP domain that regulates active RhoA population. We recently solved the structure of the BCH domain from yeast p50RhoGAP (YBCH) and showed that it maintains the adjacent GAP domain in an auto-inhibited state through the ß5 strand. Our previous WT YBCH structure shows that a unique kink at position 116 thought to be made by a proline residue between alpha helices α6 and α7 is essential for the formation of intertwined dimer from asymmetric monomers. Here we sought to establish the role and impact of this Pro116. However, the kink persists in the structure of P116A mutant YBCH domain, suggesting that the scaffold is not dictated by the proline residue at this position. We further identified Tyr124 (or Tyr188 in HBCH) as a conserved residue in the crucial ß5 strand. Extending to the human ortholog, when substituted to acidic residues, Tyr188D or Tyr188E, we observed an increase in RhoA binding and self-dimerization, indicative of a loss of inhibition of the GAP domain by the BCH domain. These results point to distinct roles and impact of the non-conserved and conserved amino acid positions in regulating the structural and functional complexity of the BCH domain.

Proline metabolic reprogramming modulates cardiac remodeling induced by pressure overload in the heart.

Metabolic reprogramming is critical in the onset of pressure overload-induced cardiac remodeling. Our study reveals that proline dehydrogenase (PRODH), the key enzyme in proline metabolism, reprograms cardiomyocyte metabolism to protect against cardiac remodeling. We induced cardiac remodeling using transverse aortic constriction (TAC) in both cardiac-specific PRODH knockout and overexpression mice. Our results indicate that PRODH expression is suppressed after TAC. Cardiac-specific PRODH knockout mice exhibited worsened cardiac dysfunction, while mice with PRODH overexpression demonstrated a protective effect. In addition, we simulated cardiomyocyte hypertrophy in vitro using neonatal rat ventricular myocytes treated with phenylephrine. Through RNA sequencing, metabolomics, and metabolic flux analysis, we elucidated that PRODH overexpression in cardiomyocytes redirects proline catabolism to replenish tricarboxylic acid cycle intermediates, enhance energy production, and restore glutathione redox balance. Our findings suggest PRODH as a modulator of cardiac bioenergetics and redox homeostasis during cardiac remodeling induced by pressure overload. This highlights the potential of PRODH as a therapeutic target for cardiac remodeling.

Seed osmopriming with polyethylene glycol (PEG) enhances seed germination and seedling physiological traits of Coronilla varia L. under water stress.

Water stress can adversely affect seed germination and plant growth. Seed osmopriming is a pre-sowing treatment in which seeds are soaked in osmotic solutions to undergo the first stage of germination prior to radicle protrusion. Seed osmopriming enhances germination performance under stressful environmental conditions, making it an effective method to improve plant resistance and yield. This study analyzed the effect of seed osmopriming with polyethylene glycol (PEG) on seed germination and physiological parameters of Coronilla varia L. Priming treatments using 10% to 30% PEG enhanced germination percentage, germination vigor, germination index, vitality index, and seedling mass and reduced the time to reach 50% germination (T50). The PEG concentration that led to better results was 10%. The content of soluble proteins (SP), proline (Pro), soluble sugars (SS), and malondialdehyde (MDA) in Coronilla varia L. seedlings increased with the severity of water stress. In addition, under water stress, electrolyte leakage rose, and peroxidase (POD) and superoxide dismutase (SOD) activities intensified, while catalase (CAT) activity increased at mild-to-moderate water stress but declined with more severe deficiency. The 10% PEG priming significantly improved germination percentage, germination vigor, germination index, vitality index, and time to 50% germination (T50) under water stress. Across the water stress gradient here tested (8 to 12% PEG), seed priming enhanced SP content, Pro content, and SOD activity in Coronilla varia L. seedlings compared to the unprimed treatments. Under 10% PEG-induced water stress, primed seedlings displayed a significantly lower MDA content and electrolyte leakage than their unprimed counterparts and exhibited significantly higher CAT and POD activities. However, under 12% PEG-induced water stress, differences in electrolyte leakage, CAT activity, and POD activity between primed and unprimed treatments were not significant. These findings suggest that PEG priming enhances the osmotic regulation and antioxidant capacity of Coronilla varia seedlings, facilitating seed germination and seedling growth and alleviating drought stress damage, albeit with reduced efficacy under severe water deficiency.

Intramolecular autoinhibition regulates the selectivity of PRPF40A tandem WW domains for proline-rich motifs.

PRPF40A plays an important role in the regulation of pre-mRNA splicing by mediating protein-protein interactions in the early steps of spliceosome assembly. By binding to proteins at the 5´ and 3´ splice sites, PRPF40A promotes spliceosome assembly by bridging the recognition of the splices. The PRPF40A WW domains are expected to recognize proline-rich sequences in SF1 and SF3A1 in the early spliceosome complexes E and A, respectively. Here, we combine NMR, SAXS and ITC to determine the structure of the PRPF40A tandem WW domains in solution and characterize the binding specificity and mechanism for proline-rich motifs recognition. Our structure of the PRPF40A WW tandem in complex with a high-affinity SF1 peptide reveals contributions of both WW domains, which also enables tryptophan sandwiching by two proline residues in the ligand. Unexpectedly, a proline-rich motif in the N-terminal region of PRPF40A mediates intramolecular interactions with the WW tandem. Using NMR, ITC, mutational analysis in vitro, and immunoprecipitation experiments in cells, we show that the intramolecular interaction acts as an autoinhibitory filter for proof-reading of high-affinity proline-rich motifs in bona fide PRPF40A binding partners. We propose that similar autoinhibitory mechanisms are present in most WW tandem-containing proteins to enhance binding selectivity and regulation of WW/proline-rich peptide interaction networks.

Biochemical characterization and metabolic reprogramming of amino acids in Soybean roots under drought stress.

Amino acids play important roles in stress resistance, plant growth, development, and quality, with roots serving as the primary organs for drought response. We conducted biochemical and multi-omics analyses to investigate the metabolic processes of root amino acids in drought-resistant (HN44) and drought-sensitive (HN65) soybean (Glycine max) varieties. Our analysis revealed an increase in total amino acid content in both varieties, with phenylalanine, proline, and methionine accumulating in both. Additionally, several amino acids exhibited significant decreases in HN65 but slight increases in HN44. Multi-omics association analysis identified 13 amino acid-related pathways. We thoroughly examined the changes in genes and metabolites involved in various amino acid metabolism/synthesis and determined core genes and metabolites through correlation networks. The phenylalanine, tyrosine, and tryptophan metabolic pathways and proline, glutamic acid and sulfur-containing amino acid pathways were particularly important for drought resistance. Some candidate genes, such as ProDH and P4HA family genes, and metabolites, such as O-acetyl-L-serine, directly affected up- and downstream metabolism to induce drought resistance. This study provided a basis for soybean drought resistance breeding.

H2S is involved in drought-mediated stomatal closure through PLDα1 in Arabidopsis.

MAIN CONCLUSION: PLDα1 promoted H2S production by positively regulating the expression of LCD. Stomatal closure promoted by PLDα1 required the accumulation of H2S under drought stress. Phospholipase Dα1 (PLDα1) acting as one of the signal enzymes can respond to drought stress. It is well known that hydrogen sulfide (H2S) plays an important role in plant responding to biotic or abiotic stress. In this study, the functions and relationship between PLDα1 and H2S in drought stress resistance in Arabidopsis were explored. Our results indicated that drought stress promotes PLDα1 and H2S production by inducing the expression of PLDα1 and LCD genes. PLDα1 and LCD enhanced plant tolerance to drought by regulating membrane lipid peroxidation, proline accumulation, H2O2 content and stomatal closure. Under drought stress, the H2O2 content of PLDα1-deficient mutant (pldα1), L-cysteine desulfhydrase (LCD)-deficient mutant (lcd) was higher than that of ecotype (WT), the stomatal aperture of pldα1 and lcd was larger than that of WT. The transcriptional and translational levels of LCD were lower in pldα1 than that in WT. Exogenous application of the H2S donor NaHS or GYY reduced the stomatal aperture of WT, pldα1, PLDα1-CO, and PLDα1-OE lines, while exogenous application of the H2S scavenger hypotaurine (HT) increased the stomatal aperture. qRT-PCR analysis of stomatal movement-related genes showed that the expression of CAX1, ABCG5, SCAB1, and SLAC1 genes in pldα1 and lcd were down-regulated, while ACA1 and OST1 gene expression was significantly up-regulated. Thus, PLDα1 and LCD are required for stomatal closure to improve drought stress tolerance.

Molecular priming with H2O2 and proline triggers antioxidant enzyme signals in maize seedlings during drought stress.

BACKGROUND: Drought and water stress impose major limitations to crops, including Maize, as they affect the plant biology at multiple levels. Drought activates the cellular signalling machinery to maintain the osmotic and ROS homeostasis for controlling plant response and adaptation to stress. Molecular priming of seeds plays a significant role in imparting stress tolerance by helping plants to remember the stress, which improves their response when they encounter stress again. METHODS: In this study, we examined the effect of priming maize seeds with H2O2 and proline, individually or in combination, on response to drought stress. We investigated the role of molecular priming on the physiological, biochemical and molecular response of maize seedlings during drought stress. RESULTS: We observed that seed-priming played a significant role in mediating stress tolerance of seedlings under drought stress as indicated by changes in growth, biochemical properties, pigment and osmolyte accumulation, antioxidant enzyme activities, gas exchange parameters and gene expression. Seed-priming resulted in reduced expression of specific miRNAs to increase target transcripts associated with synthesis of osmolytes and maintenance of ROS homeostasis for reducing potential damage to the cellular components. CONCLUSIONS: Seed-priming induced changes in the growth, biochemical properties, pigment and osmolyte accumulation, antioxidant enzyme activities, gas exchange parameters and gene expression, though the response was dependent on the genotype, as well as concentration and combination of the priming agents.

Exogenous of different elicitors: proline and ornithine on Sansevieria trifasciata under particulate matter (PM) and volatile organic compounds (VOC).

Phytoremediation has become famous for removing particulate matter (PM) and volatile organic compounds (VOC) in situ. Plants for removing PM and VOC were associated with botanical biofilters to attract pollution to the plant. On the other hand, persistent pollution exposure can lower plant health and phytoremediation effectiveness; therefore, improving plant tolerance against stress is necessary. Various elicitors can enhance plant tolerance to certain stressors. This study aims to investigate different elicitors to maintain plant health and improve the use of plants in phytoremediation for PM and VOC pollution. This experiment used Sansevieria trifasciata hort. ex Prain under PM and VOC stress. Exogenous elicitors, such as proline, ornithine, and a commercial product, were applied to the leaf parts before exposure to PM and VOC stress. The initial concentrations of PM1, PM2.5, and PM10 were 300-350, 350-450, and 400-500 µg m-3, respectively, while the VOC concentration was 2.5-3.0 mg m-3. The plant was stressed for 7 days. The result indicated that ornithine 10 mM is vital in improving plant tolerance and inducing antioxidant enzymes against PM and VOC, while proline 50 mM and a commercial product could not reduce plant stress. This study suggests that ornithine might be an important metabolite to improve plant tolerance to PM and VOC.