Methylesterase Activity Research Articles

γ-Aminobutyric acid and nitric oxide treatments preserve sensory and nutritional quality of cornelian cherry fruits during postharvest cold storage by delaying softening and enhancing phenols accumulation

During postharvest life, cornelian cherry fruits suffer from browning accompanying by sensory and nutritional quality deterioration. Cold storage isn’t along sufficiently effective for delaying browning accompanying by preserving the sensory and nutritional quality of cornelian cherry fruits during postharvest life. In this experiment, the mechanisms employed by γ-aminobutyric acid (GABA) at 0, 2.5, 5 and 10 mM and NO donor sodium nitroprusside (SNP) at 0, 250, 500 and 1000 μM on delaying browning accompanying by preserving the sensory and nutritional quality of cornelian cherry fruits during storage at 4 °C for 21 days was investigated. Our result showed that the cornelian cherry fruits treated with 5 mM GABA and 500 μM SNP exhibited higher firmness which may arise from lower cell wall degrading enzymes polygalacturonase (PG) and pectin methylesterase (PME) activity. Also, lower browning in cornelian cherry fruits treated with 5 mM GABA and 500 μM SNP during storage at 4 °C for 21 days may arise from higher phenylalanine ammonia lyase (PAL) enzyme activity along with lower polyphenol oxidase (PPO) enzyme activity giving rise to higher phenols, flavonoids and anthocyanins accumulation and superior DPPH scavenging capacity. Accordingly, our results suggest that the postharvest 5 mM GABA and 500 μM SNP treatments may be beneficial strategies for supplying firm cornelian cherry fruits with higher bioactive molecules accumulation which is crucial for consumer health.

Impact of nitric oxide on shelf life and quality of nectarine (Prunus persica var. nucipersica)

Nectarine is an emerging fruit crop in India which has immense nutritional quality and fairly good amount of antioxidants. In India, peach orchards are being replaced by nectarine primarily because of fuzzless peel. However, shelf life of nectarine is lean due to its climacteric behaviour. Hence, we attempted to observe the effect of nitric oxide (NO), using its donor compound, namely sodium nitroprusside (SNP) on postharvest life and quality of ‘Silver Queen’ nectarine fruit. In this study, fruit of ‘Silver Queen’ nectarine were treated with various concentrations of SNP (0.25 mM, 0.5 mM, 1.0 mM, 1.5 mM) after harvesting at climacteric stage of maturity. Fruit were stored at ambient condition for further analysis on daily basis, after air drying at room temperature. Our results revealed that among the various concentrations of SNP, 0.5 mM was found to be best in reducing physiological loss in weight (PLW), maintaining firmness and retaining higher phenolics, antioxidant activity, exhibiting slower increase in lipoxygenase (LOX) and pectin methylesterase (PME) activity and better quality fruit up to 8 days than 4 days of untreated fruit. Hence, postharvest dip of ‘Silver Queen’ nectarine fruit in 0.5 mM solution of SNP could be recommended for enhancing the shelf life by 4 days.

Shelf life determination of durian (Durio zibethinus) paste and pulp upon highpressure processing

Globally, there has been an increase in demand for durian. Therefore, it is important to extend the shelf life and at the same time, maintain the quality of durian. This study investigated the effect of high-pressure processing (HPP) on the shelf life of durian paste and pulp. Specifically, HPP treatments of 500 MPa for 5 min on nylon- and skin film-packed durian pulp, and 600 MPa for 5 min on nylon-packed durian paste were applied. It was found that throughout the 56-day storage period, the total soluble solids (TSS), pH and titratable acidity of durian paste and pulp showed no significant changes (p>0.05). The colour (L* values) of nylon-packed untreated durian pulp showed no significant changes (p>0.05), while the untreated durian paste and skin film-packed durian pulp showed significant changes (p 0.05) throughout the storage period. The microbial levels of all the high- pressure (HP)-treated durian samples remained below the detection limit till the end of the storage study. HP-treated durian samples showed lower enzymatic (polygalacturonase and pectin methyl esterase) activities compared to untreated sample throughout the storage period. Sensory evaluation showed no significant difference (p>0.05) between untreated and HP-treated samples. In summary, HPP effectively maintained the overall quality of durian for a minimum of 56 days.

Evidence for the Regulation of Gynoecium Morphogenesis by ETTIN via Cell Wall Dynamics.

ETTIN (ETT) is an atypical member of the AUXIN RESPONSE FACTOR family of transcription factors that plays a crucial role in tissue patterning in the Arabidopsis (Arabidopsis thaliana) gynoecium. Though recent insights have provided valuable information on ETT's interactions with other components of auxin signaling, the biophysical mechanisms linking ETT to its ultimate effects on gynoecium morphology were until now unknown. Here, using techniques to assess cell-wall dynamics during gynoecium growth and development, we provide a coherent body of evidence to support a model in which ETT controls the elongation of the valve tissues of the gynoecium through the positive regulation of pectin methylesterase (PME) activity in the cell wall. This increase in PME activity results in an increase in the level of demethylesterified pectins and a consequent reduction in cell wall stiffness, leading to elongation of the valves. Though similar biophysical mechanisms have been shown to act in the stem apical meristem, leading to the expansion of organ primordia, our findings demonstrate that regulation of cell wall stiffness through the covalent modification of pectin also contributes to tissue patterning within a developing plant organ.

Ammonium mitigates Cd toxicity in rice (Oryza sativa) via putrescine-dependent alterations of cell wall composition

In plants, different forms of nitrogen (NO3− or NH4+) affect nutrient uptake and environmental stress responses. In the present study, we tested whether NO3− and NH4+ affect the ability of rice (Oryza sativa) to tolerate the toxic heavy metal cadmium (Cd). Compared with NO3−, NH4+ treatment significantly increased chlorophyll contents and reduced Cd2+ levels in rice cultivars Nipponbare (japonica) and Kasalath (indica) grown in 0.2 mM Cd2+. NH4+ significantly reduced the pectin and hemicellulose contents and inhibited the pectin methylesterase (PME) activity in rice roots, thereby reducing the negative charges in the cell wall and decreasing the accumulation of Cd2+ in roots. In addition, NH4+ reduced the absorption and root-to-shoot translocation of Cd2+ by decreasing the expression of OsHMA2 and OsNramp5 in the root. Levels of the signaling molecule putrescine were significantly higher in the roots of both rice cultivars provided with NH4+ compared with NO3−. The addition of putrescine reduced Cd2+ contents in both rice cultivars and increased the chlorophyll content in shoots by reducing root cell wall pectin and hemicellulose contents, inhibiting PME activity and suppressing the expression of OsHMA2 and OsNramp5 in the root. Taken together, these results indicate that NH4+ treatment alleviated Cd toxicity, enabling rice to withstand the noxious effects of Cd by modifying the cell wall Cd-binding capacity due to alterations of pectin and hemicellulose contents and Cd transport, processes induced by increasing putrescine levels. Our findings suggest methods to decrease Cd accumulation in rice by applying NH4+ fertilizers.

Enzyme activity, sugar composition, microbial growth and texture of fresh Barhi dates as affected by modified atmosphere packaging.

The effects of modified atmosphere packaging (MAP) on various physicochemical quality attributes of fresh Barhi dates at the Khalal (yellow) stage were studied. Polypropylene (PP) and polyethylene (PE) plastic with varied perforation sizes (0, 50, 100 and 150µm) were evaluated for storage of date fruits at temperatures of 1, 5, 15 and 25°C up to 45days. MAP showed significant effects on fruit quality. PP date packages perforated with 150-µm perforations and stored at 5°C had the lowest acidity and microbial load. Dates packed in PE exhibited higher pectin methylesterase (PME) and polyphenol oxidase (PPO) activities than dates packed in PP. Dates stored in nonperforated packages had the highest PME, PPO and invertase activities. The maximum fructose and glucose contents were observed in PP-packaged dates stored at 15°C. Analysis of the interactions of several MAP variables revealed temperature as the major variable controlling the quality of dates. The findings showed that MAP can be effectively employed to preserve the quality and improve the shelf life of Barhi dates using PP with 150-µm perforations as the packaging material during storage for 2weeks at 5°C.

Thermal inactivation of pectin methylesterase in pineapple juice

Thermal processing is usually used by the fruit juice industry for enzyme and microbial inactivation, thus limiting organoleptic changes that affect shelf life and quality of products. Mainly the inactivation of enzymes is necessary to avoid quality changes related to cloud loss, using mild temperature that allows minor alterations in product’s sensory as well as in nutritive traits. Pineapple juice, a product obtained by diluting the concentrate juice and pasteurizing afterword shipped to Europe, has a high residual pectin methylesterase (PME) activity. In this view, the present work provides a detailed kinetic study of the effect of pasteurization on inactivation of PME in pineapple juice. The fresh juice was treated with temperatures ranging from 70 to 95 °C, for various times, until the complete denaturation of PME occurred. Results of thermal stabilization treatments showed that enzyme inactivation behaviour follows a first-order kinetic process, in the studied temperature range. Moreover, the reaction rate constants for denaturation of PME were determined; in particular, activation energy (Ea), decimal reduction time (Dref), and z value (z), were 78.2 ± 4.5 kJ/mol, 16 s (at reference temperature of 106 °C) and 36 ± 3 °C, respectively. Based on the thermal resistance data here reported to inactivate PME, a treatment of 106 °C with a mean holding time of 1 min should be employed in order to preserve cloudiness of pasteurized pineapple juice.

Metabolic and physiologic profile during the fruit ripening of three blueberries highbush (Vaccinium corymbosum) cultivars

BACKGROUND: Blueberry was introduced as a crop in Argentina about 30 years ago. Its harvesting period ranges from September to December, during the northern hemisphere (its main export destination) fall season, which makes it a profitable commercial crop. As most part of the production is exported fresh, the understanding of biochemical aspects connected with fruit firmness is crucial to improve marketable conditions. OBJECTIVE: The main purpose of this work is to explore the metabolic and physiologic changes in three highbush blueberry cultivars during maturation and the possible association with their contrasting firmness features. METHODS: Vaccinium corymbosum cv. ‘Emerald’, ‘Snowchaser’ and ‘O’Neal’, in order of decreasing firmness, were collected at green and ripe stages. Metabolites were analyzed by gas chromatography-mass spectrometry (GC-MS) and HPLC. Total phenolic compounds, pectin methyl esterase (PME) and β-galactosidase activities were quantified by colorimetric assays. RESULTS: Multivariate analysis of metabolites differentiated fruit regarding their maturation state in the first place. Malic, citric and phosphoric acids, asparagine (Asn) and mannitol were more abundant in green fruits. Conversely, mature fruits were distinguished by their higher content of citrulline and turanose. Other compounds were responsible for the differentiation between varieties: histidine (His), valine (Val), arginine (Arg), methionine (Met) and sucrose where high in ripe Snowchaser, while green and ripe Emerald had more tryptophane (Trp), glycine (Gly), phenylalanine (Phe), Trp, Gly and glucose. An interesting finding is that Emerald, the firmer variety, had less xylose content at both stages, possibly owing to a minor degree of cell wall degradation. Fold change of PME and β-galactosidase activity from green to ripe fruit demonstrated a divergent tendency in Emerald and Snowchaser compared to O’Neal. A correlation study strongly and positively connected firmness with citric acid and phenylalanine (Phe) content, while xylose, leucine (Leu) and shikimic acid were negatively related to this attribute. CONCLUSIONS: This study suggests that changes in the content of a few metabolite and activities of cell wall modifying enzymes during maturation period could be correlated with the observed difference in firmness of the blueberries studied. These findings may yield clues for improvements in fertilization protocols as well as to serve to the guided development of new varieties based on biochemical quality traits.

Down-Regulation of PpBGAL10 and PpBGAL16 Delays Fruit Softening in Peach by Reducing Polygalacturonase and Pectin Methylesterase Activity.

β-galactosidases are cell wall hydrolases that play an important role in fruit softening. However, PpBGALs mechanism impacting on ethylene-dependent peach fruit softening was still unclear. In this study, we found that PpBGAL4, -6, -8, -10, -16, and -17 may be required for ethylene-dependent peach softening and PpBGAL10, -16 may make a main contribution to it among 17 PpBGALs. Utilization of virus-induced gene silencing (VIGS) showed that fruits were firmer than those of the control at 4 and 6 days after harvest (DAH) when PpBGAL10 and PpBGAL16 expression was down-regulated. Suppression of PpBGAL10 and PpBGAL16 expression also reduced PpPG21 and PpPME3 transcription, and polygalacturonase (PG) and pectinmethylesterases (PME) activity. Overall, total cell wall material and protopectin slowly declined, water-soluble pectin slowly increased, and cellulose and hemicellulose was altered significantly at 4 DAH, relative to control fruit. In addition, PpACO1 expression and ethylene production were also suppressed at 4 DAH because of inhibiting PpBGAL10 and PpBGAL16 expression. These results suggested that down-regulation of PpBGAL10 and PpBGAL16 expression delays peach fruit softening by decreasing PG and PME activity, which inhibits cell wall degradation and ethylene production.

Salicylic acid reduces the accumulation of aluminum in Panax notoginsen root cell wall pectin via the NO signaling pathway

Salicylic acid (SA) and nitric oxide (NO) are key signal molecules involved in the reduction of Al accumulation in many plants. The purpose of this study was to investigate whether they could reduce the root content of Al and/or its binding to the root cell wall (CW) fractions in Panax notoginseng, and to investigate the corresponding regulatory mechanisms. Effects of Al treatments on the endogenous SA and NO contents of P. notoginseng were detected. Exogenous SA and paclobutrazol (PAC, a SA synthesis inhibitor) treatments were conducted to test the effects on endogenous NO content; exogenous sodium nitroprusside (SNP, a NO doner) and 2-phenyl-4,4,5,5-tetramethyl- imidazoline-1-oxyl-3-oxyde (cPTIO, a NO synthesis inhibitor) treatments were conducted to test the effects on endogenous SA content. Pectin methyltransferase (PMT) and pectin methylesterase (PME) activity and the gene expression, pectin methylesterification degree (PMD), pectin content, and the accumulation of Al in roots were also studied under the treatments described above. Al stress induced a significant increase of the activity and expression of phenylalanine ammonia-lyase (PAL), and promoted the significant increase of endogenous SA content of P. notoginseng roots. The Al promoted accumulation of endogenous NO could be enhanced by exogenous SA treatment, but was reduced by PAC. Accumulation of endogenous NO that promoted by Al could be enhanced by exogenous SA treatment, but was reduced by PAC treatment. However, SNP or cPTIO treatments had no significant effect on the Al-induced endogenous SA content of P. notoginseng. This showed that NO acted downstream of SA signaling of P. notoginseng under Al stress. Al stress can increase the activity and genes expression of PME in the roots of P. notoginseng, reduce PMD, increase CW pectin content, and thus, the binding capacity of CW pectin to Al was enhanced in P. notoginseng roots. Exogenous SA or SNP both reduced the Al-binding capacity of root CW pectin by decreasing the pectin content, and increased the PMD by inhibiting the genes expression and activity of PME. The effects of PAC or cPTIO on the above-mentioned indicators under Al stress were opposite to that of exogenous SA or SNP treatments. The Al stress induced accumulation of pectin and the reduction of PMD in the root CW of P. notoginseng could be reversed by the treatments of exogenous SA or SNP, then the Al contents in root CW pectin were reduced. Al stress activated the endogenous SA and NO signaling pathways in P. notoginseng, and NO acted downstream of SA. It showed that the Al-activated NO-SA signaling pathway contributed in the reduction of Al binding to the root under Al stress.

Effect of NaHCO3 treatments on the activity of cell-wall-degrading enzymes produced by Penicillium digitatum during the pathogenesis process on grapefruit.

This study was performed to clarify the strategies of Penicillium digitatum during pathogenesis on citrus, assessing, on albedo plugs, the effects of treatment with sodium bicarbonate (NaHCO3 ), at two different pH values (5 and 8.3), on cell-wall-degrading enzyme activity over a period of 72 h. Treatment with NaHCO3 , under alkaline pH, delayed the polygalacturonase activity for 72 h, or 48 h in the case of the pectin lyase, compared with the control or the same treatment at pH 5. In contrast, pectin methyl esterase activity rapidly increased after 24 h, in plugs dipped in the same solution. In this case, the activity remained higher than untreated or pH 5-treated plugs up to 72 h. The rapid increase in pectin methyl esterase activity under alkaline conditions is presumably the strategy of the pathogen to lower the pH, soon after the initiation of infection, in order to restore an optimal environment for the subsequent polygalacturonase and pectin lyase action. In fact, at the same time, a low pH delayed the enzymatic activity of polygalacturonase and pectin lyase, the two enzymes that actually cleave the α-1,4-linkages between the galacturonic acid residues. © 2018 Society of Chemical Industry.

Effects of high hydrostatic pressure on the overall quality of Pêra-Rio orange juice during shelf life.

The effect of high hydrostatic pressure on antioxidant activity, total phenolic compounds, physicochemical characteristics, color, pectin methylesterase activity, and microbiological count were evaluated during the shelf life of Pêra-Rio orange juice. Pressurized (520 MPa, 60 ℃, for 360 s), non-processed and pasteurized (95 ℃/30 s) orange juice were compared at zero time of storage. Pressurized and pasteurized juices were studied during a refrigerated 90-day shelf life. Pressurization did not cause expressive change in physicochemical characteristics of Pêra-Rio orange juice along shelf life, but significantly reduced pectin methylesterase residual activity to 13% and microbiological counts below detection levels up to 68 days of storage, with small counts (30.0 × 10 CFU/mL mesophilic aerobic bacteria and 20.7 × 10 CFU/mL yeast and mold) at 90 days, capable of ensuring the juice's stability along shelf life. Lightness ( L*) and b* values were significantly reduced by high hydrostatic pressure during shelf life, while a* values were significantly higher. Ascorbic acid decreased around 80% during shelf life. Antioxidant activity remained stable after processing and during storage.

Abscisic acid is involved in root cell wall phosphorus remobilization independent of nitric oxide and ethylene in rice (Oryza sativa).

Abscisic acid (ABA) is a well-studied phytohormone demonstrated to be involved in sub-sets of stress responses in plants, such as iron (Fe) deficiency and phosphorus (P) deficiency in Arabidopsis. However, whether ABA is involved in P deficiency in rice has not been frequently studied. The present study was undertaken to investigate the mechanism underlying ABA-aggravated P deficiency in rice (Oryza sativa). P deficiency decreased ABA accumulation rapidly (within 1 h) in the roots. Exogenous ABA negatively regulated root and shoot soluble P contents by decreasing pectin content, inhibiting P deficiency-induced increases in pectin methylesterase activity and expression of the phosphate transporter gene-OsPT6, thereby decreasing the re-utilization of P from the cell wall and its translocation to the shoot. Moreover, neither the nitric oxide (NO) donor sodium nitroprusside nor ethylene precursor 1-aminocyclopropane-1-carboxylic acid had any effect on ABA accumulation, and application of ABA or the ABA inhibitor fluridone also had no effect on NO production and ethylene emission. Under P deficiency, NO levels increase as quickly as ABA levels decrease, to inhibit both the ABA-induced reduction of pectin contents for the re-utilization of cell wall P and the ABA-induced down-regulation of OsPT6 for the translocation of P from roots to shoots. Overall, our results provide novel information indicating that the reduction of ABA under P deficiency is a very important pathway in the re-utilization of cell wall P in rice under P-deficient conditions, which should be a very effective mechanism for plant survival under P deficiency stress for common agronomic practice.

Phytochemical profiling of the ripening of Chinese mango (Mangifera indica L.) cultivars by real-time monitoring using UPLC-ESI-QTOF-MS and its potential benefits as prebiotic ingredients

Maturity has important effects on the phytochemical and biochemical characteristics of fruits. It affects the quality, nutritional value, harvest time and commercial operations. In this study, Keitt, Sensation and Xiangya mango cultivars in four distinct stages from southwest China were evaluated for their phytochemical profiling and antioxidant activities in real time. Furthermore, the biochemical characteristics indices polyphenol oxidase (PPO), peroxidase (POD), superoxide dismutase (SOD) and pectin methylesterase (PME) activities were determined. Antioxidant compounds such as vitamin C, total phenolic, total flavonoid and total carotenoid content were also analysed. A total of 34 phenolic compounds were identified and quantitatively monitored by UPLC-ESI-QTOF-MS. Consecutive degradation of phenolic acids and its derivatives were observed upon maturity. We found that in addition to carotenoids, phenolic acids could also be used as a measurement index of maturity in mango. Mango juices and its phenolic extracts may be used as potential prebiotics for modulating probiotic proliferation.

OsWAK11, a rice wall-associated kinase, regulates Cu detoxification by alteration the immobilization of Cu in cell walls

Wall-associated kinases (WAKs) are a family of receptor-like kinases (RLKs) with important roles against biotic and abiotic stresses in plants. Here, we reported that a rice WAK gene, OsWAK11, detoxifies excess copper by regulating the methylesterification of the cell wall. RNA interference- (RNAi-) mediated OsWAK11 knockdown in rice resulted in hypersensitivity to copper toxicity. This Cu hypersensitivity in OsWAK11-RNAi transgenic lines might result from more Cu uptake, which accumulated in the cytoplasm rather than the cell wall. Surprisingly, less Cu was accumulated in the cell wall pectin and hemicellulose of OsWAK11-RNAi transgenic lines than in wild-type plants, possibly because of decreased pectin methylesterase (PME) activity. We detected dramatically reduced expression of a key PME encoding gene, OsPME14, in OsWAK11-RNAi plants. Furthermore, disruption of OsPME14 expression could mimic the effects of OsWAK11 downregulation in plants challenged by excess Cu. Given that OsWAK11 expression is induced by excess Cu, our results indicate that plant cells activate OsWAK11 activity to modify the properties of the cell wall, thereby retaining Cu on the wall when subjected to excess Cu.

Tree Age Affects Postharvest Attributes and Mineral Content in Amrapali Mango (Mangifera indica) Fruits

The study was carried out to investigate the effect of tree age on postharvest attributes and mineral content of Amrapali mango fruits. Effect of 3 different tree ages (6, 18 and 30 years) on functional components, including the antioxidant activity (AOX), total phenols, total carotenoids, ascorbic acid and minerals like Ca, K, Mg, Fe, Zn, Cu, Mn and B along with total sugars, total soluble solids (TSS) and titratable acidity (TA), respiration rate, polygalacturonase (PG) and pectin methylesterase (PME) activities in Amrapali cultivar were studied. With tree ageing total phenols, ascorbic acid and antioxidant activity decreased whereas total carotenoids increased. Ca diminished and K elevated with the tree age progression while, B, Fe, Cu, Zn, and Mn showed an indefinite pattern. Total soluble solids and total sugars were recorded higher in 18 year old tree fruits. Fruit respiration rate, polygalacturonase and pectin methylesterase activities showed an upward trend with tree ageing. The study indicates that fruit produced from middle age group mango orchard (18 year old) suits to the requirement of consumers as well as industry.

Mechanisms regulating fruit calcium content and susceptibility to bitter pit in cultivars of apple

This work was carried out to investigate the mechanisms regulating fruit calcium (Ca) content and susceptibility to bitter pit (BP) in 'Fuji' and 'Catarina' apples (cultivars with low and high susceptibility to BP, respectively). Fruit of both cultivars were harvested at commercial maturity in an orchard located in southern Brazil, and assessed for xylem functionality and lenticels pore area (mm2 mm-2 of skin) at the distal end. Fruits were also cold stored for four months (0.0±0.5°C/95% RH) and then separated in lots without and with BP. Fruits of both cultivars without and with BP were assessed at the distal (blossom end), middle (equatorial region) and proximal (peduncle end) portions for pectin methylesterase (PME) activity in the skin and flesh tissues, and at distal portion for peroxidase (POD) and ascorbate peroxidase (APX) activities and Ca content in the flesh tissue. At harvest, 'Catarina' apples had lower xylem functionality and lower lenticels pore area at the distal end than 'Fuji' apples. 'Catarina' had higher incidence of BP after cold storage (12.7%) than 'Fuji' (2.3%). In both cultivars, fruit with BP had lower Ca content in the flesh at the distal end. Fruits with BP showed at the distal region higher POD activity in the flesh in 'Fuji' and higher PME activity in the skin in 'Catarina' than fruit without BP. Only in 'Fuji', fruits with BP had higher PME activity in the flesh tissue at the middle and distal portion than fruits without BP. The results show that impairment of xylem functionality, and reduced lenticels pore area and high PME activity in the skin tissue at the distal portion of the fruit might reduce fruit Ca content and increase the incidence of BP, especially in 'Catarina', a cultivar highly susceptible to the disorder.

The Auxin-Regulated CrRLK1L Kinase ERULUS Controls Cell Wall Composition during Root Hair Tip Growth

Root hairs facilitate a plant's ability to acquire soil anchorage and nutrients. Root hair growth is regulated by the plant hormone auxin and dependent on localized synthesis, secretion, and modification of the root hair tip cell wall. However, the exact cell wall regulators in root hairs controlled by auxin have yet to be determined. In this study, we describe the characterization of ERULUS (ERU), an auxin-induced Arabidopsis receptor-like kinase, whose expression is directly regulated by ARF7 and ARF19 transcription factors. ERU belongs to the Catharanthus roseus RECEPTOR-LIKE KINASE 1-LIKE (CrRLK1L) subfamily of putative cell wall sensor proteins. Imaging of a fluorescent fusion protein revealed that ERU is localized to the apical root hair plasma membrane. ERU regulates cell wall composition in root hairs and modulates pectin dynamics through negative control of pectin methylesterase (PME) activity. Mutant eru (-/-) root hairs accumulate de-esterified homogalacturonan and exhibit aberrant pectin Ca2+-binding site oscillations and increased PME activity. Up to 80% of the eru root hair phenotype is rescued by pharmacological supplementation with a PME-inhibiting catechin extract. ERU transcription is altered in specific cell wall-related root hair mutants, suggesting that it is a targetfor feedback regulation. Loss of ERU alters the phosphorylation status of FERONIA and H+-ATPases 1/2, regulators of apoplastic pH. Furthermore, H+-ATPases 1/2 and ERU are differentially phosphorylated in response to auxin. We conclude that ERULUS is a key auxin-controlled regulator of cell wall composition and pectin dynamics during root hair tip growth.

The Necrotrophic Fungus Macrophomina phaseolina Promotes Charcoal Rot Susceptibility in Grain Sorghum Through Induced Host Cell-Wall-Degrading Enzymes.

The cell-wall-degrading enzymes (CWDE) secreted by necrotrophs are important virulence factors. Although not unequivocally demonstrated, it has been suggested that necrotrophs induce hosts to cooperate in disease development through manipulation of host CWDE. The necrotrophic fungus Macrophomina phaseolina causes charcoal rot disease in Sorghum bicolor. An RNA-seq experiment was conducted to investigate the behavior of sorghum CWDE-encoding genes after M. phaseolina inoculation. Results revealed M. phaseolina's ability to significantly upregulate pectin methylesterase-, polygalacturonase-, cellulase-, endoglucanase-, and glycosyl hydrolase-encoding genes in a charcoal rot-susceptible sorghum genotype (Tx7000) but not in a resistant genotype (SC599). For functional validation, crude enzyme mixtures were extracted from M. phaseolina- and mock-inoculated charcoal-rot-resistant (SC599 and SC35) and -susceptible (Tx7000 and BTx3042) sorghum genotype stalks. A gel diffusion assay (pectin substrate) revealed significantly increased pectin methylesterase activity in M. phaseolina-inoculated Tx7000 and BTx3042. Polygalacturonase activity was determined using a ruthenium red absorbance assay (535 nm). Significantly increased polygalacturonase activity was observed in two susceptible genotypes after M. phaseolina inoculation. The activity of cellulose-degrading enzymes was determined using a 2-cyanoacetamide fluorimetric assay (excitation and emission maxima at 331 and 383 nm, respectively). The assay revealed significantly increased cellulose-degrading enzyme activity in M. phaseolina-inoculated Tx7000 and BTx3042. These findings revealed M. phaseolina's ability to promote charcoal rot susceptibility in grain sorghum through induced host CWDE.

The combined effect of calcium, pectin methylesterase and mild heat on frozen mango quality

Both single and mixed solutions of calcium and pectin methylesterase were studied to examine how they improve the quality of frozen mango. The result showed that calcium and pectin methylesterase had a synergistic effect on the mango, helping to improve firmness and decrease the drip loss of the frozen fruit. To increase the efficiency of the mixed solution of pectin methylesterase and calcium, this study examined three immersion temperatures (25, 40 and 50 °C). Pectin methylesterase activity, calcium content, -carotene content, firmness, drip loss and color of the samples were evaluated. The treatment at 40 °C caused high pectin methylesterase activity and calcium content. The firmness of the frozen-thawed mango increased two-fold from 1.25 to 2.50 N, and the drip loss decreased from 15.19 to 9.87 g/100 g when compared with the control samples. Moreover, the frozen-thawed mango that was immersed in pectin methylesterase and calcium at 40 °C had the highest lightness and hue value and the lowest browning index.