Water-soluble Pectin Research Articles

Physiological Mechanisms of Citrus Fruit Cracking: Study on Cell Wall Components, Osmoregulatory Substances, and Antioxidant Enzyme Activities.

Fruit cracking affects both the yield and economic efficiency of citrus; however, the underlying mechanism remains unclear. Therefore, this study focused on resistant and susceptible cultivars to identify the mechanisms underlying fruit cracking. The results showed that in 'Mingrijian', pectin morphological transformation and hemicellulose and lignin degradation in the pericarp were important contributing factors. During the critical fruit-cracking period (115-150 days after flowering), the water-soluble pectin, protopectin, and lignin contents in the pericarp of 'Daya' presented inverse changes relative to those in 'Mingrijian', thus enhancing the mechanical properties and resistance of pericarp. From 115 to 150 days after flowering, the soluble sugar content in the pulp of 'Mingrijian' increased rapidly by 97.35%, aiding in pulp water absorption and expansion. Moreover, the soluble protein content in the pericarp of 'Mingrijian' exhibited a declining trend and was lower than that of 'Daya', thus affecting the overall metabolism. The superoxide dismutase (SOD) activity in the pericarp of 'Mingrijian' gradually decreased from 115 to 180 days after flowering, while the peroxidase (POD) activity remained at a low level, resulting in weaker antioxidant capacity and lower environmental resistance. This study provides valuable insights into the mechanisms of citrus fruit cracking, laying the foundation for preventive and control strategies.

Influence of myoinositol on post-ripening and softening of Prunus salicina ‘Wushan plum’

To investigate the impact of myoinositol (MI) immersion treatment on the storage characteristics of Prunus salicina ‘Wushan Plum’, we assessed myoinositol content, ascorbic acid content, weight loss, decay rate, alteration in color, titratable acidity (TA), soluble solids (TSS), firmness, cell wall metabolism-related compounds, enzyme activities, and levels of gene expression throughout a 15-day storage period at 25 °C. The results revealed that MI treatment could increase myoinositol and ascorbic acid contents of fruit during the pre-storage period, effectively delay the color transformation and decay progression of P. salicina ‘Wushan Plum’ while maintaining elevated levels of TA and TSS. Furthermore, it suppressed the increase in weight loss and the decline in firmness. Notably, the delay in softening was more pronounced in the group treated with 100 mg L−1 MI compared to other groups. MI treatment regulated the expression levels of various genes associated with cell wall metabolism, which resulted in reduced activities of polygalacturonase (PG), pectate lyase (PL), pectin methylesterase (PME), cellulase (Cx), and β-glucosidase (β-Glu), and increased activities of phenylalanine ammonia-lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD). Furthermore, MI treatment maintained higher levels of covalently bound pectin (CSP), cellulose, and lignin, while decreasing the levels of water-soluble pectin (WSP) in the fruit. As a result, MI treatment could delay the depolymerization of cell wall polysaccharides and further delay the quality deterioration of P. salicina ‘Wushan Plum’ fruits under ambient storage environment and prolong the storage period.

Overexpression of the Rubus idaeus Polygalacturonases Gene RiPG2 Accelerates Fruit Softening in Solanum lycopersicum

The high susceptibility of raspberries to softening restricts the development of the raspberry industry. The primary causes of fruit softening are the breakdown of components linked to the cell wall and the destruction of the cell wall structure itself. Polygalacturonase (PG), a key enzyme that catalyzes pectin degradation, plays a critical role in fruit softening. However, there are currently limited studies on the mechanism of PG genes in raspberry fruit softening. In this study, a PG gene, RiPG2, was isolated from raspberry (Rubus idaeus L.). ‘Polka’ fruits and tomato plants overexpressing RiPG2 were obtained by Agrobacterium tumefaciens-mediated leaf disc transformation to elucidate the role of RiPG2 in fruit softening. The total length of the RiPG2 gene is 1185 bp, and the gene encodes a total of 394 amino acids. The GFP fusion protein was expressed at the chloroplast under laser confocal microscopy, indicating that the RiPG2 protein is localized to the chloroplasts. Phenotypic analysis revealed that the fruit firmness of three strains was considerably less than that of controls, but PG enzyme activity was increased. Overexpression of RiPG2 altered the content of cell wall components, with an increase in water-soluble pectin (WSP) and ion-bound pectin (ISP) but a decrease in protopectin, cellulose, hemicellulose, and covalently bound pectin (CSP). In addition, RiPG2 positively regulated the expression of cell wall metabolism-related genes such as SlEXP1, SlTBG4, SlXTH5, and SlPL. These results suggest that the RiPG2 gene regulates the structure and composition of the cell wall and acts synergistically with other cell wall metabolism-related genes to promote fruit softening. This study provides a new candidate gene for molecular breeding to improve raspberry firmness.

Abnormal cell wall structure caused by boron nutrient imbalance in orchards could affect psyllid feeding behaviour, resulting in epidemic variation of Asian citrus psyllid.

The control of Huanglongbing (HLB), one of the most destructive pests of citrus, relies heavily on the reduction of Asian citrus psyllid (ACP), Diaphorina citri Kuwayama. An in-depth understanding of ACP feeding behaviours among citrus plants is urgent for comprehensive management of orchards. An investigation was conducted in 37 citrus orchards in HLB epidemic areas, sampling shoots in the area with aggregation feeding of ACP (ACPf) and shoots in a neighbouring area without ACP feeding (CK), to study the interaction between leaf chemical composition and ACP psyllid feeding behaviours. Results of FTIR showed a strong absorption peak intensity, mainly representing functional groups originating from cell wall components in the leaf with ACP feeding. As compared with the control, cell wall components, such as alkali-soluble pectin, water-soluble pectin, total soluble pectin, cellulose, and hemicellulose, of the cell wall of ACPf increased by 134.0%, 14.0%, 18.0%, 12.5%, and 20.35%, respectively. These results suggest that cell wall mechanical properties significantly decreased in the term of decreases in pectin performance and cellulose mechanical properties. In addition, there was a remarkably lower boron (B) content in leaves and cell wall components with ACP feeding. Further analysis indicated that leaf B content significantly affected leaf cell wall components. Taken together, we provide evidence to demonstrate that the regional distribution of nutrient imbalance in orchards could affect psyllid feeding behaviour by weakening the cell wall structure, resulting in epidemic variation in ACP. This could help us to understand the management of psyllid infections in orchards with unbalanced nutrition.

Effect of exogenous melatonin on antioxidant properties and fruit softening of 'Fengtang' plum fruit (Prunus salicina Lindl.) during storage at room temperature.

'Fengtang' plums soften quickly and lose flavor after harvest. This study comprehensively evaluated the effect of exogenous melatonin on the fruit quality of 'Fengtang' plums. According to our findings, exogenous melatonin prevented plum fruit from losing water, delayed the decline in firmness, and preserved a high TSS/TA level. Additionally, exogenous melatonin also enhanced the activity of antioxidant enzymes and increased the non-enzymatic antioxidants, thereby further increasing the antioxidant capacity of plum fruit. Notably, exogenous melatonin delayed the degradation of covalent soluble pectin (CSP), cellulose, and hemicellulose, as well as the rise in water-soluble pectin (WSP) concentration and the activity of cell wall degrading enzymes. Further investigation using atomic force microscopy (AFM) revealed that the chain-like structure of ionic-soluble pectin (ISP) and the self-assembly network structures of CSP were depolymerized, and melatonin treatment retarded the depolymerization of pectin structures. Our results showed that exogenous melatonin preserved the postharvest quality of plum fruits by controlling fruit softness and antioxidant capacity during storage.

γ irradiation mediated the inhibitory effect of Ca2+ signals on softening of blueberry fruit during cold storage

Postharvest blueberries tend to soften and rot, resulting in serious fruit waste. Gamma (γ) irradiation can delay the softening of blueberries and improve fruit quality. Calcium is a structural component of plant cell wall and membrane, and plays a role as a second messenger in the physiological process of fruit. To explore the mechanism of inhibiting the softening of cold storage blueberry fruit by γ irradiation, ‘Bluecrop’ blueberry fruit were treated by γ irradiation at a dose of 2.5 kGy, and then combined with calcium ion (Ca2+) inhibitors and intracellular calmodulin antagonists. The Ca2+ fluorescence signals, fruit firmness, protopectin and different soluble pectin contents, cellulose and hemicellulose contents, and hydrolase activities were detected. Results showed that irradiation induced Ca2+ release from intracellular calcium store to generate fluorescence signals. Irradiation mediated the Ca2+ signals to exert a positive effect on fruit firmness of blueberries during cold storage, for the degradation of protopectin and chelator-soluble pectin to water-soluble pectin was reduced by inhibiting activities of polygalacturonase and pectin methylesterase. Therefore, γ irradiation-induced Ca2+ signals played an important role in regulation of pectin-involved fruit softening in blueberries during cold storage. This study provides a theoretical basis for the mechanism of Ca2+ signaling in blueberry storage.

Influence of pectin and hemicelluloses on physical properties of bacterial cellulose.

The properties of bacterial cellulose (BC)-based films produced by in situ biosynthesis with various polysaccharides (water-soluble pectin, arabinan, rhamnogalacturonan I, arabinoxylan, xyloglucan, glucomannan) were investigated. The addition of the polysaccharides to the bacterial growth environment changed the composition of the films by incorporating characteristic monosaccharides. BC-based films contained up to 26.7 % of non-cellulosic polysaccharides. The applied modification had a clear impact on water sorption and caused a decrease in the thermal stability of most BC films, which was connected with the depletion of geometrical dimensions of cellulose nanofibers observed with AFM. The FT-IR and Raman spectra demonstrated a decrease in % Iα of cellulose films, most notably for xyloglucan and glucomannan, as well as a change in their degree of crystallinity and the length of cellulose chains. The addition of xyloglucan had the most pronounced effect on film hardening; the other additives had a similar but lesser effect.

Xanthan gum coating delays ripening and softening of jujube fruit by reducing oxidative stress and suppressing cell wall polysaccharides disassembly

Harvested jujube fruit are prone to rapid ripening and softening during postharvest storage. In this work, jujube fruit were coated with xanthan gum (0.3%) and compared with uncoated control during storage at 20 ± 1 ºC for 15 d. Xanthan gum coating suppressed disease incidence (DI) and reduced fruit weight loss (FWL) of coated jujubes. Similarly, coating delayed reddening index development and suppressed relative ion leakage (RIL), malondialdehyde (MDA), superoxide anion (O2–•) and hydrogen peroxide (H2O2) concentrations. The coated jujubes exhibited suppressed respiration and ethylene production rates along with higher antioxidative enzymes activity. On the other side, xanthan gum coating preserved higher firmness and showed lower water-soluble pectin (WSP) along with conserved concentrations of Na2CO3-soluble pectin (SSP), cellulose (CS), hemicellulose (HCS) and chelate-soluble pectin components (CSP) owing to suppressed activities of polygalacturonase (PG), cellulase (CX), pectin methylesterase (PME) and β-galactosidase (β-gal) enzymes. The coated jujubes showed reduced total soluble solids increase and exhibited higher ascorbic acid content. So, xanthan gum coating could be applied as an eco-friendly postharvest treatment for the quality preservation of fresh jujube fruit.

Layer by layer application of chitosan and carboxymethyl cellulose coatings delays ripening of mango fruit by suppressing cell wall polysaccharides disassembly

Mango is a climacteric fruit that ripens quickly after harvest due to its climacteric nature. Edible coatings have been reported to delay the ripening of various harvested fruit. The efficacy of the applied edible coatings could be improved by using in combination as a layer-by-layer (LBL) approach. So, the influence of LBL application of chitosan (CH) and carboxymethyl cellulose (CMC) was studied on mangoes during postharvest storage at 15 °C for 20 days. Mangoes were coated with monolayers of CH (1 % w/v) and CMC (1 % w/v) as well as LBL application of CH and CMC and were compared with control. The treatment of mangoes with CH and CMC-based LBL treatment resulted in lower decay percentage and weight loss along with higher total chlorophyll pigments and suppressed total carotenoid accumulation. The LBL application of CH and CMC showed lower activity of chlorophyll degrading such as chlorophyllase (CPS), pheophytinase (Phe), Mg-dechalatase (MGD) and chlorophyll degrading peroxidase (Chl-POD) enzymes as well as reduced changes in b*, a* and L* along with a suppressed increase in ethylene (EP) and CO2 production (CPR) rates having higher antioxidant such as catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD) and superoxide dismutase (SOD) enzymes activity. In addition, mangoes coated with LBL treatment of CH and CMC exhibited lower water-soluble pectin (WSP) and higher protopectin (PP) having higher concentrations of chelate soluble (CSP) and sodium carbonate-soluble pectin (SCP). Similarly, LBL-coated mangoes showed significantly higher hemicellulose (HCLS) and cellulose (CLS) contents in contrast with control. It was observed that mangoes coated with CH and CMC-based LBL coating exhibited higher flesh firmness and showed suppressed cellulase (CS), pectin methylesterase (PME), polygalacturonase (PG) and β-galactosidase (β-Gal) enzymes activity. The concentrations of total soluble solids and ripening index were markedly lower and titratable acidity was higher in the LBL-based coating treatment in comparison with control. In conclusion, LBL treatment based on CH and CMC coatings could be used for the delay of ripening and softening of harvested mangoes.

Peeling mechanism of tomato induced by HHAIB: Microscopic, ultrastructure, chemical, physical and mechanical properties perspectives

In order to better manage the peeling degree and avoid unnecessary losses, the current work aimed to explore the peeling mechanism of a novel peeling technology, high-humidity hot air impingement blanching (HHAIB). The relationships between HHAIB peeling performance and the changes in skin temperature, skin structure, water state, pectin fractions content, and skin mechanical properties of tomatoes were analyzed. Results showed, after HHAIB treatment, the epicuticular wax was disrupted, the skin exhibited more and longer random cracks, the degradation of inner skin tissue was observed by transmission electron microscopy, the free water percentage increased resulting in water loss in the whole tomato, the water-soluble pectin contents decreased in tomato fleshes, while the contents of chelate-soluble pectin and sodium-carbonate-soluble pectin increased. HHAIB heating reduced the elongation at break, and increased Young's Modulus of tomato peel. This study revealed the HHAIB peeling mechanism and provided new insights for developing HHAIB peeling technology.

Increased weight loss and internal air space, degraded starch and pectin combined to cause pulp mealiness in ‘Oregon Spur Ⅱ’ apples during ambient storage

Pulp mealiness is a common phenomenon in ‘Delicious’ apples during ambient storage, but the underlying mechanism remains poorly understood. In the present study, fruit physiological and quality parameters, the volume of internal air space and the degree of mealiness as well as cell wall-degrading enzyme activities and pectin material content were measured in ‘Oregon Spur Ⅱ’ apple fruit during ambient storage. The results showed that the peaks of respiration rate and ethylene production of ‘Oregon Spur Ⅱ’ fruit occurred at 5 d and 10 d of storage, respectively, during which the starch and malic acid contents and firmness decreased significantly, while the fruit weight loss, the volume of internal air space and the degree of mealiness increased rapidly. Meanwhile, the activities of pectin methylesterase (PME) and pectin lyase (PL) showed a unimodal change during storage, whereas the activity of polygalacturonase (PG) decreased, and the activities of α-L-arabinofuranosidase (α-AFase) and β-galactosidase (β-Gase) as well as the contents of water-soluble pectin (WSP), chelator-soluble pectin (CSP), and sodium carbonate-soluble pectin (NSP) increased with increasing storage time. Correlation analysis showed that α-AFase, β-Gase, WSP, CSP, weight loss, the volume the air space, firmness, starch, and malic acid were significantly correlated with the degree of pulp mealiness (|r|>0.9). In conclusion, increased weight loss and internal air space, degraded starch and pectin combined to cause pulp mealiness in ‘Oregon Spur Ⅱ’ apples during ambient storage.

Physiological and molecular mechanisms of Acacia melanoxylon stem in response to boron deficiency.

Boron is an essential micronutrient for plant growth as it participates in cell wall integrity. The growth and development of Acacia melanoxylon stem can be adversely affected by a lack of boron. To explore the mechanism of boron deficiency in A. melanoxylon stem, the changes in morphological attributes, physiological, endogenous hormone levels, and the cell structure and component contents were examined. In addition, the molecular mechanism of shortened internodes resulting from boron deficiency was elucidated through transcriptome analysis. The results showed that boron deficiency resulted in decreased height, shortened internodes, and reduced root length and surface area, corresponding with decreased boron content in the roots, stems, and leaves of A. melanoxylon. In shortened internodes of stems, oxidative damage, and disordered hormone homeostasis were induced, the cell wall was thickened, hemicellulose and water-soluble pectin contents decreased, while the cellulose content increased under boron deficiency. Furthermore, plenty of genes associated with cell wall metabolism and structural components, including GAUTs, CESAs, IRXs, EXPs, TBLs, and XTHs were downregulated under boron deficiency. Alterations of gene expression in hormone signaling pathways comprising IAA, GA, CTK, ET, ABA, and JA were observed under boron deficiency. TFs, homologous to HD1s, NAC10, NAC73, MYB46s, MYB58, and ERF92s were found to interact with genes related to cell wall metabolism, and the structural components were identified. We established a regulatory mechanism network of boron deficiency-induced shortened internodes in A. melanoxylon based on the above results. This research provides a theoretical basis for understanding the response mechanism of woody plants to boron deficiency.

Mechanisms of texture and cell microstructure changes during post-ripening of ‘Cuixiang’ kiwifruit

The lack of ability to control post-ripening softening is a bottleneck that affects the economic efficiency of ‘Cuixiang’ kiwifruit. This study investigated the softening mechanisms of fruit texture and microstructural changes during post-ripening at room temperature and established a kinetic model to predict and validate shelf life. The starch content of ‘Cuixiang’ decreased, total soluble solid (TSS) and sugar–acid ratio (SAR) increased, and the texture gradually became softer during post-ripening. Microstructural changes reflected starch fragmentation and disintegration, cell structure collapse, plasmolysis, and intensified mitochondrial vacuolization and cell-wall degradation during post-ripening. Changes in cell wall polysaccharide fractions and the evolution of cell membrane lipid metabolism indicated that post-ripening was accompanied by cellulose and hemicellulose degradation. In addition, pectin components transformed into water-soluble pectin, and oxidative stress across the cell membrane caused membrane damage and rupture, increasing membrane permeability. A zero-order kinetic model of firmness was selected to accurately and reliably predict the shelf life of ‘Cuixiang’ kiwifruit.

Ripening induced degradation of pectin and cellulose affects the medium-and short-wave infrared drying characteristics of mulberry

Mulberries were categorized into five stages of ripening (D1–D5, 0.905–1.055 g/cm3) based on their density, and their physicochemical properties, tissue structure, cell wall polysaccharide properties, and drying characteristics were investigated. As mulberry ripening progressed, the TSS and water-soluble pectin content rapidly increased, while the contents of TA, hardness, chelate-, sodium carbonate-soluble pectin, hemicellulose, and cellulose decreased gradually. Pectin nanostructure and monosaccharide composition indicated that both the main and side chains of pectin undergo depolymerization. Medium- and short-wave infrared drying time initially decreased and then increased during mulberry ripening, with D4 fruits exhibiting the shortest drying time. Compared with D4 fruits, the collapse of cell structure in D5 fruits prolongs their drying time. The results demonstrate that ripeness significantly affects mulberry drying characteristics, which is related to changes in cell structure and pectin properties. Utilizing mulberry density to determine ripeness and grading is an effective approach to achieving optimal drying.

Cold shock precooling improves the firmness of chili pepper during postharvest storage and the molecular mechanisms related to pectin.

This research was conducted to explore the influence of cold shock on the firmness, a quality marker in chili pepper during 0-21 d storage and determine mechanism by cold shock impacted pectin. Chili peppers were exposed to cold shock precooling (0±2°C water/ice mixture) for 0-, 30-, 90- and 150-min, respectively. Results showed that cold shock alleviated loss of firmness throughout storage. Firmness was positively associated with sodium carbonate-soluble pectin content (r=0.44), methylation degree of CDTA-soluble pectin (r=0.82) and water-soluble pectin (WSP, r=0.87), but negatively associated with WSP content (r=-0.76), and the activities of β-galactosidase (r=-0.72) and pectinlyase (r=-0.74). Cold shock for 90min was determined to be optimal. This study confirms the applicability of cold shock precooling to maintain firmness and thereby to extend the shelf life of chili pepper.

A new pharmacological composition based on water-soluble pectin metal complexes stimulating hematopoiesis

A new pharmacological composition based on water-soluble pectin metal complexes stimulating hematopoiesis

Repression of cell wall metabolism by calcium lactate enhances the postharvest quality maintenance of Jinfeng pear fruit

Quality deterioration of pear fruit is a significant factor contributing to postharvest losses. Calcium lactate, as a food additive, was investigated in this study to estimate its impacts on quality indexes and cell wall metabolism of Jinfeng pear fruit during storage at room temperature. Results demonstrated that calcium lactate effectively maintained higher levels of titratable acidity, flesh firmness, and soluble solids content in pears. Additionally, it delayed the decline of chlorophyll content and inhibited the changes in L*, a*, b* values, and ΔE of pear fruit. The activities and gene transcriptions of pectin methyltranseliminase, pectate lyase, polygalacturonase, pectinmethylesterase, β-glucosidase, cellulase, and β-galactosidase of pears were also inhibited by calcium lactate. Moreover, calcium lactate delayed the decrease of water-insoluble pectin and cellulose contents, and inhibited the increase of water-soluble pectin content and polygalacturonic acid transeliminase activity. These results imply that postharvest application of calcium lactate can effectively retard the softening process of Jinfeng pears and maintain their postharvest quality by regulating cell wall metabolism.

Transcriptome Profiles Reveal the Promoting Effects of Exogenous Melatonin on Fruit Softening of Chinese Plum.

In this study, we investigated the effect of exogenous melatonin (MT) on cell wall metabolism leading to Chinese plum (Prunus salicina Lindl.) fruit softening. Exogenous MT treatment increased the endogenous MT content in plum fruits before fruit ripening. However, in mature plum fruits, exogenous MT treatment decreased the fruit hardness, pulp hardness, fruit elasticity, contents of ion-bound pectin, covalently-bound pectin, hemicellulose, and cellulose, and activities of xyloglucan endotransglycosylase/hydrolase and endo-β-1,4-glucanase, and increased the water-soluble pectin content, and activities of pectin methyl esterase, pectin lyase, polygalacturonase, β-galactopyranosidase, and α-L-arabinofuranosidase. Transcriptome analysis revealed that the differentially expressed genes (DEGs) associated with cell wall metabolism in the exogenous MT-treated plum fruits were mainly enriched in the pentose and glucuronate interconversions, phenylpropanoid biosynthesis, cyanoamino acid metabolism, and galactose metabolism pathways. Analysis of these DEGs revealed that exogenous MT treatment affected the expression of genes regulating the cell wall metabolism. Overall, exogenous MT treatment promotes the fruit softening of Chinese plum.

Hydrogen sulfide delays softening of banana fruit by inhibiting cell wall polysaccharides disassembly

SummaryHarvested banana undergoes rapid softening, which limits its shelf life. To delay softening, banana fruit was treated with hydrogen sulfide (H2S) emitted by 0.6 mm sodium hydrosulfide (NaHS) and stored at 15 °C for 16 days. The effects of H2S on cell wall degradation and other physiological characteristics were investigated. In comparison to control fruits, H2S‐treated bananas retained a higher level of fruit firmness, but lower hue values. Ethylene metabolism analysis suggested that H2S inhibited the production of ethylene and the accumulation of 1‐aminocyclopropane‐1‐carboxylic acid (ACC) and decreased the activities of ACC synthase (ACS) and ACC oxidase (ACO). Cell wall polysaccharides determination assays suggested that H2S treatment increased the proportion of HCl‐soluble pectin (HSP), NaOH‐soluble pectin (NSP), cellulose and hemicellulose but decreased water‐soluble pectin (WSP) in fruits. H2S treatment also inhibited the activities of polysaccharide degrading enzymes such as polygalacturonase (PG), pectin methylesterase (PME), pectin lyase (PL), cellulase (CL) and β‐galactosidase (β‐Gal). Transmission electron microscopy analysis suggested that H2S protected cell walls from structural breakdown. These results indicated that H2S is effective in delaying banana softening by regulating cell wall polysaccharide metabolism.

Low temperature inhibits pectin degradation by PpCBFs to prolong peach storage time.

Low-temperature storage is a widely used method for peach fruit storage. However, the impact of PpCBFs on pectin degradation during low-temperature storage is unclear. As such, in this study, we stored the melting-flesh peach cultivar "Fuli" at low temperature (LT, 6°C) and room temperature (RT, 25°C) to determine the effect of different temperatures on its physiological and biochemical changes. Low-temperature storage can inhibit the softening of "Fuli" peaches by maintaining the stability of the cell wall. It was found that the contents of water-soluble pectin and ionic-soluble pectin in peach fruit stored at RT were higher than those stored at LT. The enzyme activities of polygalacturonase (PG), pectate lyase (PL), and pectin methylesterase (PME) were all inhibited by LT. The expressions of PpPME3, PpPL2, and PpPG were closely related to fruit firmness, but PpCBF2 and PpCBF3 showed higher expression levels at LT than RT. The promoters of PpPL2 and PpPG contain the DER motif, which suggested that PpCBF2 and PpCBF3 might negatively regulate their expression by directly binding to their promoters. These results indicated that LT may maintain firmness by activating PpCBFs to repress pectin-degradation-related enzyme genes during storage.