Enzyme Pectin Methylesterase Research Articles

Preharvest methyl jasmonate application delays cell wall degradation and upregulates phenolic metabolism and antioxidant activities in cold stored raspberries

The effects of preharvest methyl jasmonate (MeJA) spray application on the physicochemical quality, metabolism of phenolics, and cell wall components in raspberries were investigated during a 10-day cold storage period. MeJA spray reduced firmness loss, decay incidence, and weight loss, while maintained higher levels of soluble solids content, ascorbic acid, anthocyanins and flavonoids in raspberries. Furthermore, MeJA application resulted in increased total pectin and protopectin levels, as well as lowered water-soluble pectin, and activities of pectin methyl esterase, polygalacturonase and cellulase enzymes. Additionally, MeJA treatment upregulated the phenylpropanoid pathway, leading to higher endogenous phenolics and activities of phenylalanine-ammonia lyase and shikimate dehydrogenase. In conclusion, preharvest MeJA spray application could be adopted to enhance the storage potential of cold-stored raspberries for 10 days by maintaining higher firmness, assuring better physicochemical quality, and increasing phenolic metabolism, while reducing cell wall hydrolysis.

Pulsed electric field processing of fruit juices with inactivation of enzymes with new inactivation kinetic model and determination of changes in quality parameters

Pulsed electric fields (PEF) processing of fresh grape, orange and tomato juices by 17.2–24.1 kV/cm electric field strengths, 130.0–1040.5 μs treatment times and 1.43–29.13 J/kg energies with respect to determination of the changes in the physical and bioactive properties, color parameters in addition to inactivation of pectin methyl esterase (PME), polyphenol oxidase (PPO), and lipoxygenase (LOX) enzymes were studied. In general, decrease in pH, increase in conductivity (except for grape juice), total phenolic substance content, and total antioxidant capacity with no significant change (p > 0.05) in total soluble solids were observed by PEF treatment for all juices. Except for hue value for orange juice, no significant changes (p > 0.05) were observed in color values. Inactivation of the enzymes were increased with increased energy, and calculated electrical activation energies for PME, PPO, and LOX enzymes were 8.31, 7.06, and 4.31 kJ/mol, respectively. Industrial relevanceEnzymes in addition microorganisms causing quality degradation is of great concern in fruit juice industry as most of the enzymes are resistant to processing technologies. Increased PEF treatment time provided over 95% inactivation on PME, PPO, and LOX enzymes with no adverse effect on quality properties of grape, orange, and tomato juices revealing a viable alternative to juice processing industry.

Enhancing postharvest quality and extending storage life of Booth 7 avocado (Persea americana Mill.) fruit through sodium nitroprusside (SNP) application during low-temperature storage

Postharvest quality plays a crucial role in marketability, consumer acceptability, and shelf life of avocados. This study investigates the efficacy of nitric oxide (NO) on postharvest physiology and quality of Booth 7 avocados treated with different concentrations of sodium nitroprusside (SNP) - a nitric oxide-releasing compound. Booth 7 avocados were immersed in SNP solutions (0.5 mM, 1.0 mM, and 1.5 mM), while the control fruit was immersed in distilled water for 15 min. After treatment, the fruit was stored at a temperature (T) of 8 ± 1 °C and relative humidity (RH) of 90 ± 5% for 35 days, during which the control fruit exhibited complete deterioration. The results revealed that Booth 7 avocados treated with 1.5 mM SNP concentration exhibited delayed quality changes during storage, reduced ethylene production and respiration rate, reduced alterations in soluble solids and acid content of the fruit flesh, as well as delayed changes in flesh and peel color. Additionally, the activity of total phenolic compounds (TPC), polygalacturonase (PG), and polyphenol oxidase (PPO) enzymes increased significantly, while the activity of the pectin methyl esterase (PME) enzyme was reduced. In conclusion, SNP treatment improved the quality and can be utilized as a potential postharvest preservative for Booth 7 avocados. For producers and distributors, the use of SNP in avocado postharvest management offers the potential to extend shelf life without compromising fruit quality.

Effect of various different pretreatment methods on infrared combined hot air impingement drying behavior and physicochemical properties of strawberry slices

In current work, the effect of freezing (F), ultrasound (U), and freeze- ultrasound (FU) pretreatment on infrared combined with hot air impingement drying kinetics, cell ultrastructure, enzyme activity, and physicochemical properties of strawberry slices were explored. Results showed that FU pretreatment enhanced cell membrane permeability via forming micropores, altered water status by transforming bound water into free water and thus promoted moisture diffusivity and decreased drying time by 50% compared to the control group. FU pretreatment also extensively decreased pectin methylesterase enzyme activity and maintained quality. The contents of total phenols, anthocyanins, vitamin C, antioxidant activity, and a* value of dried strawberries pretreated by FU were extensively increased compared to the control group. U and FU pretreatments were beneficial for retaining aromatic components and organic sulfides according to e-nose analyses. The findings indicate that FU is a promising pretreatment technique as it enhances drying process and quality of strawberry slices.

Effect of hydrodynamic cavitation processing on orange juice physicochemical and nutritional properties

Effect of hydrodynamic cavitation (HC) processing on pH, °brix, separation index, viscosity and color properties, retention of nutritional bioactive compounds (Vitamin-C, total phenolics, and antioxidant), and inactivation of enzyme pectin methyl esterase (PME) in freshly expressed juice from Brazilian oranges was investigated. HC at 4 bar pressures with a treatment time of 0, 10, 20, 30, 40, 50, 60, and 90 min at low temperatures (42 °C) were studied. There was no significant change in the values of pH, and TSS was noted in HC-treated juices. Further decreased flow behavior index while increased values of flow consistency index were recorded for the juice treated with HC showing a significant physical modification of the juice. Degradation and loss in vitamin C and total phenolics were observed when juices were HC-treated for a longer time. Therefore, it was concluded that HC could be used as a non-thermal method for improving the stability and physicochemical properties of Brazilian orange juice.

Application of thermosonication for guava juice processing: Impacts on bioactive, microbial, enzymatic and quality attributes

The present work explores different conditions of thermosonication (TS) processing that would ensure microbiological and enzymatic safety for guava juice while simultaneously maximizing the preservation of its quality attributes. The guava juice was subjected to TS treatment (frequency: 40 kHz; power: 200 W; Temperature: 40, 60, and 80 °C; Time: 2, 6 and 10 min) and was compared with fresh and pasteurized (90 °C/60 s) juice samples. The objectives of the research work were to determine the effect of thermosonication on the quality attributes such as total soluble solids (TSS), pH, titratable acidity, cloud value, color attributes, total phenolic contents, total flavonoid contents, antioxidant activity, ascorbic acid levels, enzymatic, microbiological, and sensory properties. The thermosonicated and pasteurized samples showed no significant (p > 0.05) changes in pH, total soluble solids, and titratable acidity. TS improved the cloud value and color attributes. Furthermore, TS enhanced total phenols (10 to17%), flavonoids (5 to 25%), antioxidant activity (10.45% to 14.55%) and retention of ascorbic acid (61.98–83.32%) relative to control. Thermosonicated sample at 80 °C/10 min gives the maximum inactivation of Pectin methyl esterase (PME), Peroxidase (POD) and Polyphenol oxidase (PPO) enzymes. While both thermosonication and pasteurization drastically decreased the microbial count to undetectable levels, only TS exhibited modest improvement in sensory qualities. The results demonstrated that TS can enhance the overall safety, quality, and commercial viability of guava juice as a practical substitute to pasteurization.

The role of PME and ADH enzymes in seed deterioration and its implication for producing high quality soybean seed

Soybean seeds are member of the orthodox seeds group which suseptable to deterioration. The low quality of soybean seeds used by farmers is one of the causes of the low soybean productivity at the farmer level. Pectin methylesterase (PME) and alcohol dehydrogenase (ADH) enzymes have been studied in relation to seed deterioration. Increase in seed moisture content is strongly suspected to be the initial occurrence and increase in PME enzyme activity which then followed by ADH enzyme activity in a series of biochemical reactions leading to the accumulation of acetaldehyde-protein adducts (APA) in soybean seeds. The APA contributes to deterioration of seeds. Thus, the increase in APA in soybean seeds may be used as an indicator of the level of deterioration of soybean seeds. Since high seed moisture content contributes to the initiation of PME activity in seeds, soybean seed production in the rainy season is not recommended because it will produce seeds with low physiological quality due to high PME activity so that the seeds cannot be stored for long-term period.

Impact of Thermo-sonication on Pectin Methylesterase (PME) Inactivation & Cloud Stability of Nagpur Mandarin Juice

Nagpur mandarin is well known globally for its excellent nutritional benefits and flavour. These all characteristics get affected during storage due to a lack of knowledge & processing techniques. One of the most important parameters which decide the quality of fruit juice during storage is cloud stability, which gets affected during storage due to the action of an enzyme named pectin methylesterase. Pectin methylesterase enzyme (PME) is a heat-resistant enzyme that impacts the juice quality by decreasing the cloud stability. Thermosonication is a technique to reduce the PME activity in juice by utilizing the principle of heat and ultrasound. Therefore, an experiment was carried out to inactivate the PME utilizing the ultrasound combined with higher temperature known as thermosensation on Nagpur mandarin (Citrus reticulata Blanco) juice. This study was initiated to calculate the effect of thermosensation treatment on the pectin methylesterase enzyme (PME) activity along with the effect of thermosensation on cloud stability in comparison with various thermal pasteurization treatments. Juice samples were thermosonicated at temperatures of 50 ℃, 55 ℃, 60 ℃, and 63 ℃ for 25, 20, 15 and 10 min respectively at a constant frequency of 40 kHz. Juice samples were also thermally pasteurized at 65 ℃, 75 ℃, 85 ℃, and 95 ℃ for 80, 60, 40, and 20 sec. Samples were analyzed after treatment at 0 days and 7 days of refrigerated storage at 4 ℃. Result indicated that thermosensation at 63 ℃ for 10 min at 40 kHz frequency showed much reduced PME activity with inactivation of 72.56% over control whereas thermal pasteurization at 95 ℃ showed inactivation of 69.31%. The same treatment also showed maximum cloud activity as compared to control and thermally pasteurized juice samples. Hence thermosensation can be used as an alternative processing technique for the inactivation of PME and cloud stability.

The adaptation of root cell wall pectin to copper toxicity in two citrus species differing in copper tolerance: remodeling and responding.

Citrus species are prone to suffer from copper (Cu) toxicity because of improper application of Cu-based agrochemicals. Copper immobilization mediated by pectin methylesterase (PME) in the root cell wall (CW) is effective for Cu detoxification. However, the underlying mechanisms of the structural modification and stress responses of citrus root CW pectin to Cu toxicity have been less discussed. In the present study, seedlings of 'Shatian pummelo' (Citrus grandis L. Osbeck) and 'Xuegan' (Citrus sinensis L. Osbeck), which differ in Cu tolerance, were irrigated with nutrient solution containing 0.5 (as control), 100, 300 or 500μM Cu for 18 weeks in sandy culture or 24h in hydroponics. At the end of treatments in the 18-week sandy culture, Cu toxicity on CW pectin content, Cu distribution, degree of pectin methylesterification (DPM) and the PME enzyme activity were discussed. At the genome-wide level, PME gene family was identified from the two citrus species, and qRT-PCR array of citrus PMEs under control and 300 μM Cu stress for 18 weeks were performed to screen the Cu-responsive PME genes. Moreover, the candidate genes that responded to Cu toxicity were further examined within 24h. The results showed that Cu toxicity increased the root CW pectin content. The root CW pectin under Cu toxicity was remodeled by upregulation of the expression of the Cu-responsive PME genes followed by increasing PME activity, which mainly promoted low methylesterased pectin level and the Cu content on root CW pectin. Compared with C. sinensis, C. grandis root CW had a lower DPM and higher Cu content on the Cu-stressed root CW pectin, contributing to its higher Cu tolerance. Our present study provided theoretical evidence for root CW pectin remodeling in response to Cu toxicity of citrus species.

硼添加对铝胁迫栝楼生长和生理的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 硼添加对铝胁迫栝楼生长和生理的影响 DOI: 10.5846/stxb202202220419 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（32001224，41702181）；2021年国家级大学生创新创业训练计划（202110345017） Effects of exogenous boron on growth and physiology of Trichosanthes kirilowii Maxim. under aluminum stress Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan)，the 2021 National Undergraduate Training Program for Innovation and Entrepreneurship 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为揭示硼对缓解栝楼（Trichosanthes kirilowii Maxim.）铝（Aluminum）毒害的生理机制，以耐铝性强的安国栝楼和耐铝性弱的浦江栝楼为材料，研究了50 μmol/L硼酸（H3BO3）对300 μmol/L Al3+胁迫下栝楼幼苗生长、铝积累、抗氧化能力和细胞壁组分的影响。结果表明：铝胁迫下，植株的根长、株高、鲜重和干重降低，超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）活性受到显著抑制，安国栝楼、浦江栝楼根尖丙二醛（MDA）含量分别增加256.1%、278.2%，细胞壁多糖含量、果胶甲酯酶（PME）活性、根尖铝积累量显著提高，果胶甲基酯化度（DM）和3-脱氧-D-甘露-辛酮糖酸（KDO）含量降低。外源硼可以缓解铝胁迫对栝楼幼苗生长的抑制作用，安国与浦江栝楼的抗氧化酶活性显著提升，MDA含量、细胞壁多糖含量、PME酶活性均降低，安国栝楼果胶DM值恢复至正常水平的91.5%，浦江栝楼KDO含量较单铝处理组上升52.0%，活性铝结合位点减少，有效降低了根尖铝含量并维持其形态结构。因此，硼信号能通过调节细胞壁多糖组分且稳定其网格结构，减少根尖对铝的吸收，同时增强抗氧化酶活性，缓解铝胁迫导致栝楼幼苗生长中的次生氧化胁迫，提高栝楼幼苗对铝毒环境的耐受性，且对耐铝性强的安国栝楼作用效果较好。研究结果可为改良酸铝胁迫下作物的生长环境提供理论指导。 Abstract:Aluminum toxicity, a major abiotic stress that inhibits plant growth and development, has become one of the main factors reducing agricultural yield. To reveal the physiological mechanism of boron on alleviating aluminum toxicity of Trichosanthes kirilowii Maxim., seedlings from Anguo (with strong Al-tolerance) and Pujiang (with weak Al-tolerance) varieties of T. kirilowii were selected for water culture experiments and the effects of boron treatment (50 μmol/L) on varieties' growth, aluminum accumulation, antioxidant capacity, and cell wall components under aluminum stress (300 μmol/L) were studied. The results showed that 300 μmol/L Al3+ stress inhibited the root length, plant height, fresh weight, and dry weight of the plant. The activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were significantly decreased, and the content of malondialdehyde (MDA) in root tip of T. kirilowii in Anguo and Pujiang varieties increased by 256.1% and 278.2%, respectively. Aluminum stress also significantly enhanced the content of cell wall polysaccharide, pectin methylesterase (PME) activity, and root tip aluminum accumulation. However, the degree of pectin methyl-esterification (DM) and the content of 3-deoxy-d-mannose-octanoic acid (KDO) were strongly inhibited. Exogenous boron could alleviate the inhibitory effect of aluminum stress on the growth of T. kirilowii seedlings. The antioxidant enzyme activities of T. kirilowii in Anguo and Pujiang varieties were increased significantly. The MDA content, cell wall polysaccharide content, and PME enzyme activity were decreased. In addition, the pectin DM value of Trichosanthes in Anguo variety returned to 91.5% of the normal level, and the KDO content of T. kirilowii in Pujiang variety increased by 52.0% compared with that in the single aluminum treatment group. As a result, the active aluminum binding sites decreased, effectively reducing the aluminum content in the root tip and maintaining its morphological structure. Therefore, boron improved the tolerance of T. kirilowii seedlings to aluminum toxic environment by regulating the polysaccharide components of cell wall and stabilizing its grid structure to reduce the absorption of aluminum by root tips, and enhancing the activity of antioxidant enzymes to alleviate the secondary oxidative stress in the growth of T. kirilowii seedlings, which has a better effect on Anguo variety with stronger tolerance to aluminum toxicity. The research in this paper can provide theoretical guidance for improving the environment for crop growth under acid-aluminum stress. 参考文献 相似文献 引证文献

Advances in Physiological, Transcriptomic, Proteomic, Metabolomic, and Molecular Genetic Approaches for Enhancing Mango Fruit Quality.

Mango (Mangifera indica L.) is a nutritionally important fruit of high nutritive value, delicious in taste with an attractive aroma. Due to their antioxidant and therapeutic potential, mango fruits are receiving special attention in biochemical and pharmacognosy-based studies. Fruit quality determines consumer's acceptance, and hence, understanding the physiological, biochemical, and molecular basis of fruit development, maturity, ripening, and storage is essential. Transcriptomic, metabolomic, proteomic, and molecular genetic approaches have led to the identification of key genes, metabolites, protein candidates, and quantitative trait loci that are associated with enhanced mango fruit quality. The major pathways that determine the fruit quality include amino acid metabolism, plant hormone signaling, carbohydrate metabolism and transport, cell wall biosynthesis and degradation, flavonoid and anthocyanin biosynthesis, and carotenoid metabolism. Expression of the polygalacturonase, cutin synthase, pectin methyl esterase, pectate lyase, β-galactosidase, and ethylene biosynthesis enzymes are related to mango fruit ripening, flavor, firmness, softening, and other quality processes, while genes involved in the MAPK signaling pathway, heat shock proteins, hormone signaling, and phenylpropanoid biosynthesis are associated with diseases. Metabolomics identified volatiles, organic acids, amino acids, and various other compounds that determine the characteristic flavor and aroma of the mango fruit. Molecular markers differentiate the mango cultivars based on their geographical origins. Genetic linkage maps and quantitative trait loci studies identified regions in the genome that are associated with economically important traits. The review summarizes the applications of omics techniques and their potential applications toward understanding mango fruit physiology and their usefulness in future mango breeding.

Design of a Protein with Improved Thermal Stability by an Evolution‐Based Generative Model

AbstractEfficient design of functional proteins with higher thermal stability remains challenging especially for highly diverse sequence variants. Considering the evolutionary pressure on protein folds, sequence design optimizing evolutionary fitness could help designing folds with higher stability. Using a generative evolution fitness model trained to capture variation patterns in natural sequences, we designed artificial sequences of a proteinaceous inhibitor of pectin methylesterase enzymes. These inhibitors have considerable industrial interest to avoid phase separation in fruit juice manufacturing or reduce methanol in distillates, averting chromatographic passages triggering unwanted aroma loss. Six out of seven designs with up to 30 % divergence to other inhibitor sequences are functional and two have improved thermal stability. This method can improve protein stability expanding functional protein sequence space, with traits valuable for industrial applications and scientific research.

Design of a Protein with Improved Thermal Stability by an Evolution-Based Generative Model.

Efficient design of functional proteins with higher thermal stability remains challenging especially for highly diverse sequence variants. Considering the evolutionary pressure on protein folds, sequence design optimizing evolutionary fitness could help designing folds with higher stability. Using a generative evolution fitness model trained to capture variation patterns in natural sequences, we designed artificial sequences of a proteinaceous inhibitor of pectin methylesterase enzymes. These inhibitors have considerable industrial interest to avoid phase separation in fruit juice manufacturing or reduce methanol in distillates, averting chromatographic passages triggering unwanted aroma loss. Six out of seven designs with up to 30 % divergence to other inhibitor sequences are functional and two have improved thermal stability. This method can improve protein stability expanding functional protein sequence space, with traits valuable for industrial applications and scientific research.

Rootstock effects on bitter pit incidence in 'Honeycrisp' apples are associated with changes in fruit's cell wall chemical properties.

Bitter pit (BP) is a physiological disorder of apples that often appears during or after cold storage. Despite being defined as a calcium deficiency disorder, BP is a complex process that is not only affected by the total Ca2+ content in the fruit but also by the proper cellular Ca2+ homeostasis and partitioning. Early investigations have also suggested that rootstocks could affect BP development and severity. In the present study, rootstock effects on BP development were assessed on ‘Honeycrisp’ trees that were grafted on 14 different rootstocks (B.10, G.11, G.202, G.214, G.30, G.41, G.935, G.969, M.26 EMLA, M.9, V.1, V.5, V.6, and V.7). We evaluated BP incidence at harvest, and three months after cold storage for four, and three growing seasons, respectively. BP incidence was significantly reduced in ‘Honeycrisp’ trees on B.10 compared to other rootstocks, whereas trees on V.6 showed the highest percentage of BP at harvest and after cold storage. ‘Honeycrisp’ apples were collected from three different rootstocks (B.10, G.41, and V.6) two months after cold storage and evaluated for mineral nutrient composition, Ca2+ homeostasis, and cell wall properties, e.g., pectin content, pectin de-esterification rate and pectin methylesterase (PME) activity. Water-soluble and insoluble pectin content was markedly higher in fruits from B.10 than in G.41 and V.6. We also observed increased PME enzyme activity and a greater degree of water-insoluble pectin de-esterification in ‘Honeycrisp’ apples from V.6 compared to those from B.10. A significantly higher Ca2+ was found in the fruits from B.10 than G.41 and V.6. Higher Ca2+ and lower Mg2+ levels were also observed in the cell wall and water-insoluble pectin fractions of the fruits from B.10 compared to G.41 and V.6. However, the ratio of cell wall-bound Ca2+ to total Ca2+ was lower in B.10 compared to G.41 and V.6. Together, our results indicate that the tolerance of B.10 to BP could be attributed to a reduced PME activity and lower pectin de-esterification level, which in turn reduced the amount of Ca2+ cross-linked with pectin, and probably increased the apoplastic free calcium concentrations that is essential for maintaining cell membrane integrity and reducing BP development.

Postharvest Exogenous Melatonin Treatment of Table Grape Berry Enhances Quality and Maintains Bioactive Compounds during Refrigerated Storage

Table grape berries are classified as a perishable crop that deteriorates quickly after harvest. The application of melatonin after harvest was found to be effective for retarding senescence and slowing ripening. In the current study, we tested the influence of two melatonin concentrations (50 and 100 µmol) as a postharvest application on quality, bioactive compounds, and enzyme activities of grape berries cv “Crimson” stored at 0 ± 1 °C and 90% relative humidity (RH) for 35 days. Our results indicated that melatonin application extends the shelf-life of berries by reducing weight loss and maintaining total soluble solids (TSS), titratable acidity (TA), berry adherence strength, and firmness. Melatonin treatment also reduced pectin methyl esterase (PME) and polygalactouranase (PG) enzyme activities compared to the control. Moreover, O2•− and H2O2 rates in berries were reduced by high melatonin concentration. Moreover, peroxidase (POD) and catalase (CAT) enzyme activities were increased by melatonin application. Our findings suggested using melatonin postharvest to increase shelf life and maintain quality attributes during refrigerated storage, which could be advantageous on a large scale.

Transcriptome-Guided Identification of Pectin Methyl-Esterase-Related Enzymes and Novel Molecular Processes Effectuating the Hard-to-Cook Defect in Common Bean (Phaseolus vulgaris L.).

The hard-to-cook defect in common beans is dictated by the ability to achieve cell separation during cooking. Hydrolysis of pectin methyl-esters by the pectin methyl-esterase (PME) enzyme influences cell separation. However, the contributions of the PME enzyme and the cell wall to the hard-to-cook defect have not been studied using molecular tools. We compared relevant molecular processes in fast- and slow-cooking bean varieties to understand the mechanisms underpinning the hard-to-cook defect. A PME spectrophotometric assay showed minor differences in enzyme activity between varieties. Meanwhile, a PME HMMER search in the P. vulgaris genome unveiled 113 genes encoding PMEs and PME inhibitors (PMEIs). Through RNA sequencing, we compared the gene expression of the PME-related genes in both varieties during seed development. A PME (Phvul010g080300) and PMEI gene (Phvul005g007600) showed the highest expression in the fast- and slow-cooking beans, respectively. We further identified 2132 differentially expressed genes (DEGs). Genes encoding cell-wall-related enzymes, mainly glycosylphosphatidylinositol mannosyltransferase, xyloglucan O-acetyltransferase, pectinesterase, and callose synthase, ranked among the top DEGs, indicating novel relations to the hard-to-cook defect. Gene ontology mapping revealed hydrolase activity and protein phosphorylation as functional categories with the most abundant upregulated DEGs in the slow-cooking bean. Additionally, the cell periphery contained 8% of the DEGs upregulated in the slow-cooking bean. This study provides new insights into the role of pectin methyl-esterase-related genes and novel cell wall processes in the occurrence of the hard-to-cook defect.

Postharvest quality response of pears with beeswax coatings during long term cold storage

ABSTRACT Lipid-based edible coatings are effective in maintaining the chemical and sensory characteristics of fruits for long-term storage by inhibiting the rate of respiration and transpiration. With this view, an investigation was conducted on the preservation of postharvest quality of pears using beeswax coating through modulating respiration and ripening associated enzymes during long-term cold storage. Asian pears (Pyrus pyrifolia L. cv. ‘Patharnakh’) were coated with beeswax (0 g, 20 g, 30 g, 40 g L−1) and stored at 0–1 °C and 90–95% relative humidity for 70 d. The results showed that the beeswax coatings maintained fruit firmness and quality parameters and exhibited lesser activities of fruit softening enzymes pectin methylesterase, polygalacturonase and cellulase during the cold storage. Furthermore, at an optimum concentration beeswax coatings retarded the oxidative browning, a decline in ascorbic acid levels and total phenolic content of pears. Nevertheless, at the end of storage, the highest concentration (40 g L−1) of beeswax coatings exhibited higher browning index (BI) and polyphenol oxidase activity (PPO) even more than the untreated fruits. Therefore, the optimum concentration of 30 g L−1 beeswax coating is suggested to preserve the quality of ‘Patharnakh’ pear through modulation of respiration and ripening enzymes during long-term cold storage.

Selenate regulates the activity of cell wall enzymes to influence cell wall component concentration and thereby affects the uptake and translocation of Cd in the roots of Brassica rapa L

Selenium (Se) can be used to counteract cadmium (Cd) toxicity in plants. However, mechanisms underlying the alleviation of Cd toxicity by Se have not been completely elucidated, especially those by which Se reduces Cd translocation. A hydroponic experiment was performed to illustrate the regulatory mechanisms of Cd transport by selenate (Se (VI)) in pakchoi (Brassica rapa L., LvYou 102). The results showed that this plant had a high accumulation capacity for Cd, and Se(VI) addition restricted Cd translocation from roots to shoots. Se(VI) exposure stimulated the concentrations of pectins and hemicellulose II but reduced the concentration of hemicellulose I in the roots. In many cases, the enzymes pectin methylesterase, polygalacturonase, and β-galactosidase were dose-dependently triggered by Se(VI) under Cd exposure, but root calcium concentration was significantly lowered (p < 0.05). Xyloglucan endoglycosidase (hydrolase) was triggered by Se(VI) under 2 mg L−1 Cd exposure and cellulase was generally activated by Se(VI) under Cd stress. The above results suggest that Se(VI) up-regulates pectin methylesterase activity, stimulates synthesis of pectins, and down-regulates root Ca concentration to release free carboxyl groups to combine Cd. In this study, the relationships between enzyme activity (e.g., peroxidase, superoxidase and β-galactosidase), hydrogen peroxide, cell wall structure strengthening/loosening, and Cd toxicity affected by Se(VI) were also discussed.

Kinetics of structural change of pineapple (Ananas comosus) under the influence of PME (Pectin methylesterase)

The structure of pineapple ((Ananas comosus) is hard and brittle, but it is easy to soften under the influence of high temperature during processing. Understanding the structure, arrangement and chemical reactivity of pectin in the cell wall is key to predicting and controlling changes in cluster structure. There are many different methods to affect the pectin composition to create an insoluble calcium pectate complex to keep the connection between cells, keep the structure for pineapple. The addition of the pectin methylesterase enzyme (PME) extracted from tomato to pineapple is one of the recent researched trends with the aim of improving the structural change of pineapple due to heat. Based on the recommendations made from previous studies on enzyme addition to pineapple, in this study, experiments were conducted on the influence of the order of addition of PME and CaCl2, the effect of temperature of PME addition, and the influence of PME activity on the structural change of pineapple.

Potassium enhances cadmium resistance ability of Panax notoginseng by brassinolide signaling pathway-regulated cell wall pectin metabolism

The mechanism of how potassium (K) attenuates cadmium (Cd)-induced demethylation and anabolism of cell wall (CW) pectin through the brassinolide (BR) signaling pathway was verified in Panax notoginseng (Burk.). The P. notoginseng pectin methylesterase gene (PnPME1) was cloned and functionally verified in tobacco. Pectin and BR metabolism, Cd content and the pectin methylation degree (PMD) were detected in response to K, 2,4-epibrassinolide (EBL), and brassinazole treatments of P. notoginseng and tobacco under Cd stress. Activity of the main root pectin methylesterase enzyme (PME) was promoted by 22.29% under the EBL treatment, and Cd content increased by 29.03% under Cd stress. Potassium reduced PME activity and Cd content in main root pectin by 61.03% and 50.73%, respectively, under the EBL and Cd co-treatment. Potassium inhibited the promoting effects of Cd stress on the expression of PnPME1 by 57.04%. Potassium also inhibited expression of BR synthesis genes PnDET2, PnROT3, PnCYP90A1, and PnBR6OX1 by 65.61%, 52.02%, 47.36%, and 55.16%, respectively, and reduced the accumulation of Cd. The PnPME1 was located in the CW. The activity of transgenic tobacco root PME was higher than that of the wild-type, while the PMD was significantly lower. The regulatory effects of K and EBL on tobacco root pectin metabolism were consistent with those in P. notoginseng. In conclusion, K downregulated the expression of BR synthesis genes in P. notoginseng roots under Cd stress and reduced the production of BRs, which inhibited PnPME1 expression. The reduction in PME activity increased the PMD, which reduced the accumulation of Cd.