Pectin Methylesterase Research Articles

A methyl esterase from Bifidobacterium longum subsp. longum reshapes the prebiotic properties of apple pectin by triggering differential modulatory capacity in faecal cultures.

Pectin structures have received increasing attention as emergent prebiotics due to their capacity to promote beneficial intestinal bacteria. Yet the collective activity of gut bacterial communities to cooperatively metabolize structural variants of this substrate remains largely unknown. Herein, the characterization of a pectin methylesterase, BpeM, from Bifidobacterium longum subsp. longum, is reported. The purified enzyme was able to remove methyl groups from highly methoxylated apple pectin, and the mathematical modelling of its activity enabled to tightly control the reaction conditions to achieve predefined final degrees of methyl-esterification in the resultant pectin. Demethylated pectin, generated by BpeM, exhibited differential fermentation patterns by gut microbial communities in invitro mixed faecal cultures, promoting a stronger increase of bacterial genera associated with beneficial effects including Lactobacillus, Bifidobacterium and Collinsella. Our findings demonstrate that controlled pectin demethylation by the action of a B. longum esterase selectively modifies its prebiotic fermentation pattern, producing substrates that promote targeted bacterial groups more efficiently. This opens new possibilities to exploit biotechnological applications of enzymes from gut commensals to programme prebiotic properties.

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.

Boron modulates cell wall structure that alleviate aluminum toxicity-induced root growth defects in citrus

Based on the soil acidification situation in citrus plantation of southern China and even worldwide, it's essential to explore improved methods for resistant aluminum (Al) toxicity in plant. Trifoliate (Poncirus trifoliate (L) Raf.) is the most common rootstock in China. The ambition of this research was to illustrate the influence of boron (B) on Al bound in cell wall (CW) and the mechanism in trifoliate seedlings. Healthy seedlings were exposed to 0 or 300 µM AlCl3·6H2O with 10 µM B (H3BO3, control) and 50 µM B, respectively. The results displayed that Al accumulated in roots and root tips during Al exposure. However, Al content in root rips was reduced under B sufficient that reflected by lower morin fluorescence intensity compared to B10-treated roots. More specifically, B addition abates the Al content in root CW, manifested in lower Al content in pectin and hemicellulose 1 (HC1), with HC1 being more prominent. Moreover, B addition inhibited the pectin methyl-esterase (PME) activity to reduce pectin content, while increasing the xyloglucan endotransglucosylase (XET) and xyloglucan endotransglucosylase-hydrolase (XEH) activity. Thereby HC1 content was decreased, ultimately suppressing the bound site of Al in pectin and HC1, and diminished Al content in CW with B supply. Collectively, our results illustrate that B supply was attributed to the mitigation effect of B on Al toxicity by induced devaluation of Al accumulation in CW, which was associated with the reduction of binding Al with pectin and HC1 by regulating compounds of CW through adjusting CW enzymes (PME, XET, and XEH).

Nanocellulose as a Novel Cryoprotectant to Improve the Quality of Frozen Sour Cherries

Recent studies suggest that nanocelluloses may help protect frozen foods’ structure, thereby preserving quality parameters during storage. This study examined the impact of nanocellulose treatment on the frozen quality of sour cherries. Nanocellulose produced from pistachio hull was incorporated into sour cherries using vacuum impregnation, and its cryoprotective role was assessed using three different freezing techniques: static, air-blast, and individual quick frozen (IQF). Multivariate analysis of variance (MANOVA) demonstrated the interactive effects of the parameters. During 6 months of storage, nanocellulose pretreatment resulted in significantly lower drip loss, ion leakage, and color difference while retaining high levels of anthocyanin content and antioxidant capacity compared to the non-treated group. Texture analysis also showed that using nanocellulose could compensate for the disadvantage of slow freezing. Pectin methylesterase (PME) activity values fitted to 2nd order kinetic, and the highest residuals were determined in static freezing. Strong correlations (P < 0.01) were found between drip loss and color difference (r = 0.662), hardness and ion leakage (r = 0.605), and color difference and aw values (r = 0.628).Graphical

The role of water distribution, cell wall polysaccharides, and microstructure on radish (Raphanus sativus L.) textural properties during dry-salting process

Radish (Raphanus sativus L.) undergoes texture changes in their phy-chemical properties during the long-term dry-salting process. In our study, we found that during the 60-day salting period, the hardness and crispness of radish decreased significantly. In further investigation, we observed that the collaborative action of pectin methylesterase (PME) and polygalacturonase (PG) significantly decreased the total pectin, alkali-soluble pectin (ASP), and chelator-soluble pectin (CSP) content, while increasing the water-soluble pectin (WSP) content. Furthermore, the elevated activities of cellulase and hemicellulase directly led to the notable fragmentation of cellulose and hemicellulose. The above reactions jointly induced the depolymerization and degradation of cell wall polysaccharides, resulting in an enlargement of intercellular spaces and shrinkage of the cell wall, which ultimately led to a reduction in the hardness and crispness of the salted radish. This study provided key insights and guidance for better maintaining textural properties during the dry-salting process of radish.

Effect of pectinase produced by Bacillus velezensis W17-6 on methanol content and overall quality of kiwifruit wine

Kiwifruit, a climacteric-fruit susceptible to rapid deterioration, attains considerable value upon transformation into kiwifruit wine, thereby increasing its added value. However, a noteworthy challenge arises from its high pectin content, which negatively affects byproduct quality, necessitating pectinase treatment during processing. Commercial pectinases exhibit heightened pectin esterase activity, giving rise to safety apprehensions due to augmented methanol content during kiwifruit pectin hydrolysis. In this study, Bacillus velezensis W17-6 was screened for its high pectinase activity coupled with low pectin esterase activity. The resultant crude pectinase named PBV was acquired through fed-batch-fermentation and partial purification. Subsequently, PBV was deployed in the fermentation of Xuxiang kiwifruit wine, and its impact on overall quality was assessed through diverse analyses. The results indicated that Xuxiang kiwifruit wine with PBV treatment outperformed counterparts treated with commercial pectinases. PBV treatment not only yielded superior clarity (83.75% ± 0.47%) and juice yield (81.60% ± 0.47%) but also increased the total flavonoids content in Xuxiang kiwifruit wine by 1.2 times compared to commercial pectinase. Notably, the methanol content of PBV-treated Xuxiang kiwifruit wine was significantly lower at 36.13 ± 1.83 mg/L than that of wines treated with two commercial pectinases. PBV-treated kiwifruit wine also exhibited elevated concentrations of volatile compounds such as phenethyl alcohol, ethyl undecanoate, lauric aldehyde, isobutyric acid, and myrcene. Impressively, PBV-treated kiwifruit wine surpassed other wines in both electronic and artificial sensory analyses. In summary, PBV exhibits substantial potential in the production of low-methanol, high-quality kiwifruit wine, enhancing the flavor and nutritional value while minimizing methanol production and improving the safety profile.

Blue light treatment delays postharvest ripening of kiwifruit by suppressing ethylene biosynthesis, starch degradation, and cell wall metabolism

The study aimed to investigate the effects of blue light (BL) on the postharvest ripening and softening of kiwifruit. The postharvest ripening of kiwifruit were significantly inhibited by BL; 100 μmol m−2 s−1 light intensity exhibited the best effect. The delay of postharvest ripening of kiwifruit by BL was associated with the inhibition of total soluble solids accumulation, reduction in respiratory rate and ethylene production as well as 1-aminocyclopropane-1-carboxylate synthase and 1-aminocyclopropane-1-carboxylic acid oxidase activities. Moreover, it also inhibited starch degradation and related enzyme activities (α-amylase and β-amylase), prevented the degradation of protopectin, cellulose and hemicellulose while promoting the accumulation of water soluble pectin. Additionally, it suppressed the activities of polygalacturonase, pectinlyase, pectin methylesterase, and cellulase. Transcriptome and gene expression analyses showed that BL-treated kiwifruit had lower expression levels of genes involved in ethylene biosynthesis, starch degradation, and cell wall metabolism, compared with the dark controls. BL also altered transcription factor responses to light, such as v-myb avian myeloblastosis viral oncogene homolog (MYB) and basic helix-loop-helix (bHLH) families. In summary, this study analyzed the physiological and molecular mechanisms by which BL delays the postharvest ripening of kiwifruit and provides a new preservation method for the postharvest quality maintenance of kiwifruit.

Assessing the impact of isochoric freezing as a preservation method on the quality attributes of orange juice.

Isochoric (constant volume) freezing is a novel food preservation technology that has demonstrated the ability to preserve food products at subfreezing temperatures in an unfrozen state, thereby avoiding the detrimental effects of ice formation. It minimizes the quality loss of fresh fruits and juices, increases their nutrient content, and reduces microbial counts. Orange juice (OJ) samples were subjected to conventional freezing (CF) and isochoric freezing (IF) for 7 days and then stored at 4°C for an additional 7 days. We evaluated the microbiological and physicochemical quality of CF and IF OJ before and after storage. The IF was performed at three different conditions: -5°C/73MPa, -10°C/93MPa, and -15°C/143MPa. The results indicate that the total aerobic count of OJ remained below the detection limit after heat treatment, 7 days of CF and 7 days of IF. Yeast and mold counts increased in fresh and CF OJ after 7 days of storage at 4°C, whereas IF OJ remained below the detection limit. Less color difference was observed in IF (-15°C/143MPa) OJ compared to heat-treated and CF OJ. Heat treatment inactivated 42% of pectin methylesterase (PME), whereas 7-day long IF increased PME activity up to 150%. Additionally, IF (-15°C/143MPa) OJ showed reduced pulp sedimentation, which can be advantageous, as sedimentation in juices has been a recognized technological issue in the juice industry. Ascorbic acid level was significantly higher in IF (-15°C/143MPa) OJ compared to fresh and CF OJ after storage.

An ethylene response factor AcERF116 identified from A. catechu is involved in fruitlet abscission

Procedural abscission of outer reproductive organs during flower and fruit development occurs in most plant lineages. Undesired abscission, such as fruitlet shedding causes considerable yield loss in many fruit-producing species. Ethylene is one of the key factors regulating organ abscission. However, the participants involved in the ethylene-mediated abscission pathway remains largely unidentified. In this study, we focused on the ethylene response transcription factors (ERFs) regulating fruitlet abscission in an industrial tree species, A. catechu. A total of 165 ERF genes have been found in the A. catechu genome and eight of these showed distinct expression between the “about-to-abscise” and “non-abscised” samples. An AcERF116 gene with high expression level in the fruit abscission zone (FAZ) was selected for further study. Overexpression of the AcERF116 gene accelerated cell separation in the abscission zone (AZ) and promoted pedicel abscission in transgenic tomato lines. The PG (ploygalacturonase) activity was enhanced in the FAZs of A. catechu fruitlets during ethylene-induced fruitlet abscission, while the PME (pectin methylesterase) activity was suppressed. In addition, cytosolic alkalization was observed in the AZs during abscission in both tomato and A. catechu. Our results suggest that AcERF116 plays a critical role in the crosstalk of ethylene and fruitlet abscission in A. catechu.

A Comparative Study of Five Apple Cultivars Linking Biochemical Changes at Different Developmental Stages with Storage Textural Quality

Biochemical changes in the cell wall composition and activity of cell wall-modifying enzymes of five apple cultivars, Royal Gala (Gala), Aurora Golden Gala (Aur), Splendour (Spl), Honeycrisp (HC), and Ambrosia (Amb), collected from the 2016 growing season in the early growth phases, namely 40 and 70 days after full bloom (DAFB), at harvest maturity, and after 20 weeks of storage were investigated in relation to the textural changes at harvest maturity through to 20 weeks of storage. Assessing apple texture with a single-point measurement of firmness using a penetration test to a depth of approximately 8 mm in apples may not be an ideal measurement for assessing apple textural quality. Pectin methyl esterase (PME) activity at early developmental stages may be predictive of textural quality after storage. This work also found that β-D-galactosidase (BGAL) and α-L-arabinofuranosidase (AFAS) activities at early developmental stages may be important factors affecting textural quality after storage. Additionally, the degree of methylesterification (DME) assessed with FTIR on apple flesh material at the early developmental stages was strongly positively correlated (r2 ≥ +0.891 to +0.963, p ≤ 0.05) with textural quality after storage, including crispness, indicating that FTIR could serve as a rapid screening tool for textural quality at early developmental stages on minimally processed starting material.

Characterization, antioxidant activity and in vitro digestion of hawthorn pectin prepared by gradient ethanol precipitation

Four modified hawthorn pectin fractions (MHPs), named MHP-30, MHP-50, MHP-70 and MHP-90, were obtained by ultrasonic-assisted pectin methyl esterase modification and gradient ethanol precipitation. The results indicated that all four MHPs were composed of galacturonic acid, galactose, xylose, arabinose, glucose and mannose in different proportions. With the increase of the ethanol concentration, the molecular weight, esterification degree and galacturonic acid content of MHPs all decreased, whereas the arabinose content and branching degree increased. The structural characterization from XRD, SEM, and FT-IR showed that four MHPs exhibited amorphous structure, similar functional groups, diverse surface morphologies. Besides, in vitro antioxidant assays confirmed that MHP-70 and MHP-90 exhibited stronger total antioxidant activities than MHP-30 and MHP-50. The results of simulated saliva-gastrointestinal digestion showed that the molecular weight of MHP-70 and MHP-90 remained stable, yielded small amounts of reducing sugars, and were resistant to digestion in the human upper digestive tract. Overall, MHP-70 and MHP-90 shown great potential as novel natural antioxidants, which are expected to be good carbon sources for the utilization of intestinal microorganisms.

Comparative transcriptomic profile of two mandarin varieties during maturation reveals pectinase regulating peelability

Peelability is an important fruit quality trait of citrus. Pectinase is a group of heterozygous enzymes that function in pectin degradation, which is implicated in fruit ripening and softening. Previously we established a method to quantify citrus peelability through two mechanical indexes (peel-pulp adherence and peel resistance of penetration), and exhibited the genetic diversity of peelability in mandarins (Citrus reticulata Blanco). With this method, the present study first confirmed that Clementine is an easy-peeling mandarin in comparison with Fremont, and both showed increasingly easy peeling as the fruits matured. A range of measurements for the two mandarins at three maturation stages demonstrated that peelability had negative correlation with pectin contents but positive with pectinase activity. Subsequently, RNA sequencing was performed for comparative transcriptomic profiling of the two varieties at three maturation stages. We identified 12322 differentially expressed genes (DEGs) in total. Through comparative time-course analysis, the gene expression patterns were displayed with 12 clusters each in albedo and flavedo. Some cell wall-related gene ontology terms were over-represented in albedo and flavedo Cluster6. We mined 153 genes encoding pectinase (pectin methylesterase, polygalacturonase, pectin lyase (PL), beta-galactanase, pectin acetylesterase and alpha-arabinofuranosidase) in silica from Clementine genome, and 78 of them were significantly expressed in the peel of Clementine or Fremont, whereas 62/60 belonged to the DEGs in albedo/flavedo. In weighted correlation network analysis, six/five out of eight/nine modules in albedo/flavedo had eigengene values that were significantly correlated with the two mechanical indexes, pectin contents and pectinase activity, and six/eight pectinase genes were present in the co-expression networks. Based on the results of multi-approach bioinformatics analysis, three PL genes (Ciclev10004783m.g, Ciclev10020423m.g and Ciclev10031429m.g) were highlighted as potential regulators for peelability. This study provides clues for understanding the molecular basis of the regulation of citrus peelability, and proposes pectinase as a target for peelability-oriented breeding of citrus.

Strigolactones alleviate AlCl3 stress by vacuolar compartmentalization and cell wall blocking in apple.

Poor management and excess fertilization of apple (Malus domestica Borkh.) orchards are causing increasingly serious soil acidification, resulting in Al toxicity and direct poisoning of roots. Strigolactones (SLs) are reported to be involved in plant responses to abiotic stress, but their role and mechanism under AlCl3 stress remain unknown. Here, we found that applying 1 μm GR24 (an SL analoge) significantly alleviated AlCl3 stress of M26 apple rootstock, mainly by blocking the movement of Al through cell wall and by vacuolar compartmentalization of Al. RNA-seq analysis identified the core transcription factor gene MdWRKY53, and overexpressing MdWRKY53 enhanced AlCl3 tolerance in transgenic apple plants through the same mechanism as GR24. Subsequently, we identified MdPMEI45 (encoding pectin methylesterase inhibitor) and MdALS3 (encoding an Al transporter) as downstream target genes of MdWRKY53 using chromatin immunoprecipitation followed by sequencing (ChIP-seq). GR24 enhanced the interaction between MdWRKY53 and the transcription factor MdTCP15, further increasing the binding of MdWRKY53 to the MdPMEI45 promoter and inducing MdPMEI45 expression to prevent Al from crossing cell wall. MdWRKY53 also bound to the promoter of MdALS3 and enhanced its transcription to compartmentalize Al in vacuoles under AlCl3 stress. We therefore identified two modules involved in alleviating AlCl3 stress in woody plant apple: the SL-WRKY+TCP-PMEI module required for excluding external Al by blocking the entry of Al3+ into cells and the SL-WRKY-ALS module allowing internal detoxification of Al through vacuolar compartmentalization. These findings lay a foundation for the practical application of SLs in agriculture.

Safety evaluation of an extension of use of the food enzyme pectinesterase from the genetically modified Aspergillus oryzae strain AR-962.

The food enzyme pectinesterase (pectin pectylhydrolase; EC 3.1.1.11) is produced with the genetically modified Aspergillus oryzae strain AR-962 by AB Enzymes GmbH. A safety evaluation of this food enzyme was made previously, in which EFSA concluded that this food enzyme did not give rise to safety concerns when used in five food manufacturing processes. Subsequently, the applicant requested to extend its use to two additional processes. In this assessment, EFSA updated the safety evaluation of this food enzyme for uses in a total of seven food manufacturing processes. As the food enzyme-total organic solids (TOS) is removed from the final foods in three food manufacturing processes, the dietary exposure to the food enzyme-TOS was estimated only for the remaining four processes. Dietary exposure was up to 0.575 mg TOS/kg body weight (bw) per day in European populations. When combined with the NOAEL reported in the previous opinion (1000 mg TOS/kg bw per day, the highest dose tested), the Panel derived a margin of exposure of at least 1739. Based on the data provided for the previous evaluation and the revised margin of exposure, the Panel concluded that this food enzyme does not give rise to safety concerns under the revised intended conditions of use.

Phosphorus deficiency-induced cell wall pectin demethylesterification enhances cadmium accumulation in roots of Salix caprea

Regions affected by heavy metal contamination frequently encounter phosphorus (P) deficiency. Numerous studies highlight crucial role of P in facilitating cadmium (Cd) accumulation in woody plants. However, the regulatory mechanism by which P affects Cd accumulation in roots remains ambiguous. This study aims to investigate the effects of phosphorus (P) deficiency on Cd accumulation, Cd subcellular distribution, and cell wall components in the roots of Salix caprea under Cd stress. The results revealed that under P deficiency conditions, there was a 35.4% elevation in Cd content in roots, coupled with a 60.1% reduction in Cd content in shoots, compared to the P sufficiency conditions. Under deficient P conditions, the predominant response of roots to Cd exposure was the increased sequestration of Cd in root cell walls. The sequestration of Cd in root cell walls increased from 37.1% under sufficient P conditions to 66.7% under P deficiency, with pectin identified as the primary Cd binding site under both P conditions. Among cell wall components, P deficiency led to a significant 31.7% increase in Cd content within pectin compared to P sufficiency conditions, but did not change the pectin content. Notably, P deficiency significantly increased pectin methylesterase (PME) activity by regulating the expression of PME and PMEI genes, leading to a 10.4% reduction in the degree of pectin methylesterification. This may elucidate the absence of significant changes in pectin content under P deficiency conditions and the concurrent increase in Cd accumulation in pectin. Fourier transform infrared spectroscopy (FTIR) results indicated an increase in carboxyl groups in the root cell walls under P deficiency compared to sufficient P treatment. The results provide deep insights into the mechanisms of higher Cd accumulation in root mediated by P deficiency.

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 ozone treatment on the decay and cell wall metabolism during the postharvest storage of cantaloupe

Cantaloupe is a popular summer fruit with immense market potential in China. However, the cantaloupe fruits generally soften rapidly after harvest, which dramatically reduces their economic value. The ozone treatment has been found to be effective in delaying the softening of cantaloupe fruit. The results indicated that ozone treatment significantly inhibited the mycelial growth of Fusarium hypha. The ozone treatment was able to delay the decline of total soluble solids, lower the respiration rate, and maintain the fruit's firmness without damaging fruit quality. The study also indicated that the activity and gene expression of cell wall degrading enzymes such as polygalacturonase (PG), pectin methylesterase (PME), β-galactosidase (β-gal), cellulose (Cx), and α-l-arabinofuranosidase (α-l-Af), were inhibited under ozone treatment, which also suppressed the degradation of cell wall components associated with fruit softening (protopectin, soluble pectin, cellulose, and hemicellulose). These changes may contribute to the maintenance of cell wall components, thereby delaying the fruit softening. In conclusion, these results suggested that ozone can improve the fruit quality of cantaloupe by suppressing postharvest fungal diseases and delaying fruit softening, which provides a theoretical basis for further research on cell wall metabolism during cantaloupe storage.

An in-depth investigation on the presence of methanol in Garcinia cambogia fruits and rinds: Role of pectin methyl esterase and indigenous fungi

The presence of methanol in fruits is a concern due to its toxicity and the consequent health implications. Garcinia cambogia fruits and Garcinia cambogia rinds showed methanol at 238 ± 15.07 and 355 ± 18.21 ppm, respectively. The enzyme, pectin methyl esterase (PME), associated with production of methanol was also detected with an activity 5.63 ± 0.41 and 2.75 ± 0.14 U/mL, respectively, in fruits and rinds. Furthermore, a fungi isolated from Garcinia cambogia, and identified as Aspergillus aculeatus by morphology and 18S rRNA gene/ITS/D1-D2 (∼700 bp) sequencing, also produced extracellular PME (7.67 ± 0.76 U/mL) at pH 3 to yield 166 ± 5.74 ppm methanol. The molecular weight of partially purified PMEs with 60–70 % ammonium sulphate from G. cambogia fruits, G. cambogia rinds and A. aculeatus of was ∼45, ∼25, and ∼35 kDa, could produce 55.33 ± 2.74, 41.67 ± 0.86, and 74.67 ± 0.19 ppm methanol, and displayed maximum activity at pH 7, 7 and 5, and 35 °C, 35 °C and 40 °C, respectively. The enzyme kinetics, (Km and Vmax), thermal inactivation kinetic parameters (kd, t1/2 and d-value), and thermodynamic parameters (Ed, ΔH°, ΔG°, and ΔS°) of PME from A. aculeatus were superior over PME from G. cambogia fruits and G. cambogia rinds. This investigation confirmed the production of both PME and methanol by both fungi and G. cambogia.

Discovery and Transcriptional Profiling of Penicillium digitatum Genes That Could Promote Fungal Virulence during Citrus Fruit Infection.

Green mold caused by Penicillium digitatum (Pers.:Fr.) Sacc is the most prevalent postharvest rot concerning citrus fruits. Using the subtractive suppression hybridization (SSH) technique, different P. digitatum genes have been identified that could be involved in virulence during citrus infection in the early stages, a crucial moment that determines whether the infection progresses or not. To this end, a comparison of two P. digitatum strains with high and low virulence has been carried out. We conducted a study on the gene expression profile of the most relevant genes. The results indicate the importance of transcription and regulation processes as well as enzymes involved in the degradation of the plant cell wall. The most represented expressed sequence tag (EST) was identified as PDIP_11000, associated with the FluG domain, which is putatively involved in the activation of conidiation. It is also worth noting that PDIP_02280 encodes a pectin methyl esterase, a cell wall remodeling protein with a high expression level in the most virulent fungal strains, which is notably induced during citrus infection. Furthermore, within the group with the greatest representation and showing significant induction in the early stages of infection, regulatory proteins (PDIP_68700, PDIP_76160) and a chaperone (PDIP_38040) stand out. To a lesser extent, but not less relevant, it is worth distinguishing different regulatory proteins and transcription factors, such as PDIP_00580, PDIP_49640 and PDIP_78930.

Genome-wide analysis of the PME gene family reveals its role in suppressing fruit lignification in pear

In pears, the presence of stone cells adversely affects fruit quality. Pectin methylesterase (PME) plays various roles in plant biology, including lignin biosynthesis. However, only a limited fraction has been functionally characterized, and the distribution and function of PME in many Rosaceae trees remain unexplored. In this study, we identified 396 putative PME family candidate genes, with 81 in Pyrus bretschneideri, 92 in Malus domestica, 62 in Fragaria vesca, 65 in Prunus mume, 15 in Pyrus communis, and 81 in Pyrus pyrifolia. Leveraging insights from model plants, we categorized PME family genes into four groups. Additionally, the evolution of the PME gene family was shaped by various gene duplication events, primarily dispersed duplication, influenced by purifying selection. A specific gene, Pbr031522.1, designated PbPME35, emerged as a candidate associated with lignin biosynthesis in pear fruits, supported by RNA-seq data. The role of PbPME35 in repressing lignification was validated through its overexpression in pear callus and Arabidopsis. Overall, our findings highlight the ability of PbPME35 to reduce lignin content in pear fruit by downregulating the expression levels of lignin biosynthesis genes. These findings provide new insights into the characteristics of PME genes and their role in regulating lignification in pear fruits.