Pectin Methylesterase Activity Research Articles

Identification and Analysis of the Mechanism of Stem Mechanical Strength Enhancement for Maize Inbred Lines QY1

Enhancing stalk strength is a crucial strategy to reduce lodging. We identified a maize inbred line, QY1, with superior stalk mechanical strength. Comprehensive analyses of the microstructure, cell wall composition, and transcriptome of QY1 were performed to elucidate the underlying factors contributing to its increased strength. Notably, both the vascular bundle area and the thickness of the sclerenchyma cell walls in QY1 were significantly increased. Furthermore, analyses of cell wall components revealed a significant increase in cellulose content and a notable reduction in lignin content. RNA sequencing (RNA-seq) revealed changes in the expression of numerous genes involved in cell wall synthesis and modification, especially those encoding pectin methylesterase (PME). Variations in PME activity and the degree of methylesterification were noted. Additionally, glycolytic efficiency in QY1 was significantly enhanced. These findings indicate that QY1 could be a valuable resource for the development of maize varieties with enhanced stalk mechanical strength and for biofuel production.

The transcription factors ZAT5 and BLH2/4 regulate homogalacturonan demethylesterification in Arabidopsis seed coat mucilage.

The level of methylesterification alters the functional properties of pectin, which is believed to influence plant growth and development. However, the mechanisms that regulate demethylesterification remain largely unexplored. Pectin with a high degree of methylesterification is produced in the Golgi apparatus and then transferred to the primary cell wall where it is partially demethylesterified by pectin methylesterases (PMEs). Here, we show that in Arabidopsis (Arabidopsis thaliana) seed mucilage, pectin demethylesterification is negatively regulated by the transcription factor ZINC FINGER FAMILY PROTEIN5 (ZAT5). Plants carrying null mutations in ZAT5 had increased PME activity, decreased pectin methylesterification, and produced seeds with a thinner mucilage layer. We provide evidence that ZAT5 binds to a TGATCA-motif and thereby negatively regulates methylesterification by reducing the expression of PME5, HIGHLY METHYL ESTERIFIED SEEDS (HMS)/PME6, PME12, and PME16. We also demonstrate that ZAT5 physically interacts with BEL1-LIKE HOMEODOMAIN2 (BLH2) and BLH4 transcription factors. BLH2 and BLH4 are known to modulate pectin demethylesterification by directly regulating PME58 expression. The ZAT5-BLH2/4 interaction provides a mechanism to control the degree of pectin methylesterification in seed coat mucilage by modifying each transcription factor's ability to regulate the expression of target genes encoding PMEs. Taken together, these findings reveal a transcriptional regulatory module comprising ZAT5, BLH2 and BLH4, that functions in modulating the de-methylesterification of homogalacturonan in seed coat mucilage.

Role of Silicon in Counteracting Cadmium Stress in Pea Plants (Pisum sativum L.): Insights Into Cadmium Binding Mechanisms and Pectin Methylesterase Activity

Role of Silicon in Counteracting Cadmium Stress in Pea Plants (Pisum sativum L.): Insights Into Cadmium Binding Mechanisms and Pectin Methylesterase Activity

Melatonin-Induced Chromium Tolerance Requires Hydrogen Sulfide Signaling in Maize.

Both melatonin and hydrogen sulfide (H2S) mitigate chromium (Cr) toxicity in plants, but the specific interaction between melatonin and H2S in Cr detoxification remains unclear. In this study, the interaction between melatonin and H2S in Cr detoxification was elucidated by measuring cell wall polysaccharide metabolism and antioxidant enzyme activity in maize. The findings revealed that exposure to Cr stress (100 μM K2Cr2O7) resulted in the upregulation of L-/D-cysteine desulfhydrase (LCD/DCD) gene expression, leading to a 77.8% and 27.3% increase in endogenous H2S levels in maize leaves and roots, respectively. Similarly, the endogenous melatonin system is activated in response to Cr stress. We found that melatonin had a significant impact on the relative expression of LCD/DCD, leading to a 103.3% and 116.7% increase in endogenous H2S levels in maize leaves and roots, respectively. In contrast, NaHS had minimal effects on the relative mRNA expression of serotonin-Nacetyltransferase (SNAT) and endogenous melatonin levels. The production of H2S induced by melatonin is accompanied by an increase in Cr tolerance, as evidenced by elevated gene expression, elevated cell wall polysaccharide content, increased pectin methylesterase activity, and improved antioxidant enzyme activity. The scavenging of H2S decreases the melatonin-induced Cr tolerance, while the inhibitor of melatonin synthesis, p-chlorophenylalanine (p-CPA), has minimal impact on H2S-induced Cr tolerance. In conclusion, our findings suggest that H2S serves as a downstream signaling molecule involved in melatonin-induced Cr tolerance in maize.

Calcium polypeptide mitigates Cd toxicity in rice via reducing oxidative stress and regulating pectin modification.

Calcium polypeptide plays a key role during cadmium stress responses in rice, which is involved in increasing peroxidase activity, modulating pectin methylesterase activity, and regulating cell wall by reducing malondialdehyde content. Cadmium (Cd) contamination threatens agriculture and human health globally, emphasizing the need for sustainable methods to reduce cadmium toxicity in crops. Calcium polypeptide (CaP) is a highly water-soluble small molecular peptide acknowledged for its potential as an organic fertilizer in promoting plant growth. However, it is still unknown whether CaP has effects on mitigating Cd toxicity. Here, we investigated the effect of CaP application on the ability to tolerate toxic Cd in rice. We evaluated the impact of CaP on rice seedlings under varying Cd stress conditions and investigated the effect mechanism of CaP mitigating Cd toxicity by Fourier transform infrared spectroscopy (FTIR), fluorescent probe dye, immunofluorescent labeling, and biochemical analysis. We found a notable alleviation of Cd toxicity by reduced malondialdehyde content and increased peroxidase activity. In addition, our findings reveal that CaP induces structural alterations in the root cell wall by modulating pectin methylesterase activity. Altogether, our results confirm that CaP not only promoted biomass accumulation but also reduced Cd concentration in rice. This study contributes valuable insights to sustainable strategies for addressing Cd contamination in agricultural ecosystems.

Exogenous proline regulates pectin demethylation by rescuing pectin methylesterase functioning of cell wall from Cr(VI) toxicity in rice plants

BackgroundPlants are equipped with several sophisticated mechanisms to deal with heavy metals (HMs) toxicity. Cell walls, which are rich in pectin, are important in the sequestration and compartmentalization of HMs. Pectin demethylation is carried out by pectin methylesterase (PME), which is a crucial activity in cell walls for the adsorption of HMs. This study focused on the factors that contribute to chromium (Cr) adsorption in rice plants exposed to Cr(VI) treatments without proline (Pro) “Cr(VI)” and with Pro “Pro + Cr(VI)” application.ResultsThe results exhibited that when rice plants were treated with Cr(VI), their PME activity decreased, because Cr(VI) was bound to certain isoforms of PME and prevented the demethylation of pectin. The application of Pro increased PME activity by promoting the transcription of several PME-related genes. These genes were recognized on the basis of their similarity with PME genes in Arabidopsis. Gene expression variation factors (GEVFs) between the “Cr(VI)” and “Pro + Cr(VI)” treatments revealed that OsPME7 and OsPME9 have the highest positive GEVF values than other OsPME genes of rice. In addition, Pro application increased pectin content significantly in rice plants exposed to Cr(VI) stress. Proline application also leads to an increased concentration of Cr in rice roots compared with “Cr(VI)” treatments alone.ConclusionsThese findings suggest that Pro increased Cr(VI) adsorption in cell walls of rice plants by enhancing the PME activity and pectin content when exposed to “Cr(VI)” treatments, mainly regulated by OsPME7 and OsPME9.Graphical

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.

Enhancing strawberry quality and resistance to Botrytis cinerea using calcareous seaweed-derived Ca2+/carrageenan extracts

The dilute HCl pretreatment of the calcareous red alga, Liagora viscida, either at room temperature or 100 °C, produced Ca2+/carrageenan-containing extracts. Dipping strawberries in these extracts for 10 s demonstrated their ability to maintain various quality and nutritional traits during cold storage. The weight loss of the fruits after 7 days at 4 °C was reduced to 2.48–2.63 % in the treatments, compared to 3.26 % in the control. The treatments were effective in retaining the contents of vitamin C, titratable acidity, and phenolics, compared to marked reductions in the control. Additionally, the levels of anthocyanins, flavonoids, and the total antioxidant capacity were enhanced during cold storage. The treated fruits also showed higher chitinase activities, while the activities of cellulase, polygalacturonase, and pectin methylesterase (PME) showed remarkable reductions. The application of the extract derived at 100 °C reduced the decay caused by Botrytis cinerea decay to 34 % and 63.26 % after 3 and 4 days of infection, respectively, compared to 55.09–97 % in the untreated control. This reduction was concomitant with higher anthocyanins, flavonoids, and chitinase, and lower cellulase and PME in this treatment. The levels of malondialdehyde indicated less stressed fruits during both cold storage and fungal infection. Overall, the treatments promoted systemic resistance in the fruits, enhancing their ability to defend against pathogens. These results suggest the promising utilization of calcareous macroalgae as a sustainable biomass for developing a cost-effective and eco-friendly preservative to extend the shelf-life of strawberries during cold storage and enhance their resistance to pathogens.

Pectin methylesterase activities in reproductive tissues of maize plants with different haplotypes of the Ga1 and Ga2 cross incompatibility systems.

Total PME activity in reproductive tissues was related to haplotypes at maize cross incompatibility loci, suggesting that these loci function by controlling PME activity. In maize, the pollination outcome depends on the haplotypes of the interacting male gametophyte (germinated pollen) and female sporophyte (silk) at several cross-incompatibility loci. Functional alleles (-S haplotypes) of the cross-incompatibility loci Ga1 and Ga2, both encode two pectin methylesterases (PMEs), one that is expressed in silk and the other in pollen. We examined total PME activity in reproductive tissues containing functional and null haplotypes at the Ga1 or Ga2 loci. In pollinated silks, there was a correlation between total PME activity and the -S haplotype pollen in both Ga1 and Ga2 systems. We did not detect a significant relationship between PME activity and pollination outcome of either system. We re-examined previously reported active site amino acid substitutions in PMEs encoded by cross incompatibility loci. We observed that different active site substitutions are present in the pollen and silk PMEs of cross incompatibility loci and these differences are conserved across Ga1, Ga2 and Tcb-1. This work establishes a relationship between total PME activity and the haplotypes of the Ga1 locus in pollinated silks.

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

AbstractRecent 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 Abstract

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.

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.

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.

Epigenetic modification of a pectin methylesterase gene activates apoplastic iron reutilization in tomato roots.

Iron (Fe) distribution and reutilization are crucial for maintaining Fe homeostasis in plants. Here, we demonstrate that the tomato (Solanum lycopersicum) Colorless non-ripening (Cnr) epimutant exhibits increased Fe retention in cell wall pectin due to an increase in pectin methylesterase (PME) activity. This ultimately leads to Fe deficiency responses even under Fe-sufficient conditions when compared to the wild type (WT). Whole-genome bisulfite sequencing revealed that modifications to cell wall-related genes, especially CG hypermethylation in the intron region of PECTIN METHYLESTERASE53 (SlPME53), are involved in the Cnr response to Fe deficiency. When this intron hypermethylation of SlPME53 was artificially induced in WT, we found that elevated SlPME53 expression was accompanied by increased PME activity and increased pectin-Fe retention. The manipulation of SlPME53, either through overexpression in WT or knockdown in Cnr, influenced levels of pectin methylesterification and accumulation of apoplast Fe in roots. Moreover, CG hypermethylation mediated by METHYLTRANSFERASE1 (SlMET1) increased SlPME53 transcript abundance, resulting in greater PME activity and higher Fe retention in cell wall pectin. Therefore, we conclude that the Cnr mutation epigenetically modulates SlPME53 expression by SlMET1-mediated CG hypermethylation, and thus the capacity of the apoplastic Fe pool, creating opportunities for genetic improvement of crop mineral nutrition.

Physical, Chemical and Enzymatic Changes in Amla (Emblica officinalis) Fruit during Growth and Maturation.

Amla (Emblica officinalis) is one of the most prominent fruits in terms of nutritional and medicinal properties and is utilized for the preparation of many traditional processed foods and in Ayurvedic formulations. This study aims to investigate the enzyme activity and physical and chemical quality parameters during the growth and development stages of amla fruit for the determination of proper harvesting time to get optimum nutrient contents of fruit. The amla fruits of the chakaiya variety were harvested at 135 to 270 days after fruit set (DAFS) in 2021 and 2022 to study the various physical, chemical and enzymatic changes during growth and maturation. The geometrical and gravimetric attributes of the fruit, viz. diameter, height, weight, volume, surface area, sphericity, aspect ratio, and radius of curvature increased. However, density decreased with the growth and maturation of the fruit. Furthermore, the rolling resistance, yellowness index and firmness of the fruit increased during the entire harvesting period of 135 to 270 DAFS. Total soluble solids and titratable acidity of the fruits increased only up to 195 DAFS and after that, continuously decreased. In contrast, ascorbic acid concentration grew in the entire growth and development period. Tannic, phenolic compounds and naringin content of the fruit steadily dropped until the final stage of harvest. Pectin Methyl Esterase (PME) activity was detected very low, 0.009 unit/ml at 135 DAFS, but as the fruit grew and matured, activity increased to 0.307 unit/ml at 270 DAFS. Polygalactouronase (PG) activity was not detected until 210 DAFS and, thereforesignificantly increased with maturity. Considering the optimal value of all studied physical, chemical and enzymatic attributes of the fruit during the entire harvesting period of 135 to 270 DAFS, the optimal harvesting time of the fruit was 210 DAFS.

Synergistic Influence of Melatonin-Hydrocolloid Coating on Decay and Senescence of Nectarine (Prunus persica var. nucipersica) during Supermarket Storage Conditions

Nectarines have remarkable nutritional value, low caloric content, and are rich in antioxidants. However, despite substantial local and global demand, their susceptibility to rapid spoilage during peak summer harvest is limited. To address this issue, the current study investigated the potential benefits of using melatonin (MLT), an antioxidant biomolecule, in combination with edible hydrocolloid coatings like carboxymethylcellulose (CMC) and gum Arabic (G.A.) on ‘Snow Queen’ nectarine fruits. The nectarines were treated with various combinations of coatings, including 1% and 1.5% CMC, 8% and 10% G.A., and 0.1 mM melatonin. These coated and non-coated samples were stored under standard supermarket conditions (18 ± 1 °C, 85–90% R.H.) for 16 days. The outcomes demonstrated that the most effective treatment was the combination of 1% CMC with 0.1 mM melatonin. This treatment significantly (p ≤ 0.05) reduced the rate of respiration, curbed fruit decay by approximately 95%, minimized weight loss by around 42%, and maintained approximately 39% higher levels of total phenol content and roughly 30% greater antioxidant (AOX) activity. These positive effects were accompanied by preserved firmness and overall quality attributes. Moreover, the treatment extended the shelf life to 16 days through retarding senescence and suppressing the activities of lipoxygenase (LOX) and pectin methylesterase (PME), all without compromising the functional qualities of the nectarine.

Pectin methylesterase inhibitors GhPMEI53 and AtPMEI19 improve seed germination by modulating cell wall plasticity in cotton and Arabidopsis

The germination process of seeds is influenced by the interplay between two opposing factors: pectin methylesterase (PME) and pectin methylesterase inhibitor (PMEI), which collectively regulate patterns of pectin methylesterification. Despite the recognized importance of pectin methylesterification in seed germination, the specific mechanisms that govern this process remain unclear. In this study, we demonstrated that the overexpression of GhPMEI53 is associated with a decrease in PME activity and an increase in pectin methylesterification. This leads to the softening of the cell wall in seeds, which positively regulates cotton seed germination. AtPMEI19, the homologue in Arabidopsis thaliana, plays a similar role in seed germination to GhPMEI53, indicating a conserved function and mechanism of PMEI in seed germination regulation. Further studies revealed that GhPMEI53 and AtPMEI19 directly contribute to promoting radicle protrusion and seed germination by inducing cell wall softening and reducing mechanical strength. Additionally, the pathways of ABA and GA in the transgenic materials underwent significant changes, suggesting that GhPMEI53/AtPMEI19-mediated pectin methylesterification serves as a regulatory signal for the related phytohormones involved in seed germination. In summary, GhPMEI53 and its homologs alter the mechanical properties of cell walls, influencing the mechanical resistance of the endosperm or testa. Moreover, they impact cellular phytohormone pathways (e.g., ABA, GA) to regulate seed germination. These findings enhance our understanding of pectin methylesterification in cellular morphological dynamics and signaling transduction, and contribute to a more comprehensive understanding of the PME/PMEI super-gene family in plants.

Effects of transport vibration on storage quality and expression of genes related to cell wall metabolism of winter jujube (Zizyphus jujuba Mill. cv. Dalidongzao)

Winter jujube (Zizyphus jujuba Mill. cv. Dalidongzao) is susceptible to machinery damage due to its high moisture content. The present study investigates the impact of varying levels of vibration acceleration on the softening and quality deterioration of winter jujubes through utilization of a simulated transport platform. The results demonstrated that, in comparison to the control group, winter jujubes treated with vibration exhibited a higher susceptibility to decay and weight loss. Additionally, they displayed an elevated respiration intensity and experienced a significant depletion of nutrients. The vibration promoted an increase in enzyme activity of polygalacturonase (PG), pectin methylesterase (PME) and cellulase (Cx), upregulated gene expression, and induced a reduction in pectin, cellulose and hemicellulose content, ultimately resulting in the softening of winter jujube. The hardness of winter jujube decreased by 34.87%, 37.80% and 44.92% in the shelf life under vibration accelerations of 0.25g, 0.5g and 0.75g, respectively, whereas it only decreased by 28.60% in the control group. In addition, the damage caused by vibration was also observed in the microstructure of peel and pulp. The findings demonstrate that the vibrational impact significantly influenced the quality of winter jujube, resulting in a reduced shelf life and diminished commodity value.