Chilling Injury In Peach Fruit Research Articles

Membrane lipid metabolism influences chilling injury during cold storage of peach fruit

Peach fruit is prone to chilling injury (CI) during long-term low temperature (LT) storage, and develops protective mechanisms against LT stress. This study revealed that 4 °C storage induced the occurrence of CI in peach fruit by promoting the expression of membrane lipid metabolism genes and phosphatidic acid (PA) accumulation, and stimulated a protective mechanism for peach fruit against LT by increasing diacylglycerol (DAG), triacylglycerol (TAG) and several phosphatidylcholine (PC) components in the later storage stage. In contrast, 0 °C delayed the occurrence of CI in peach fruit by delaying the degradation of phospholipids, upregulation of fatty acid desaturase (FAD) and the process of fatty acid unsaturation, and maintaining higher levels of PC and PE. Results from this study provide new information on the mechanism of CI in peach fruit, and lay the foundation for the transcriptional regulation mechanism of CI and cold tolerance in peach fruit mediated by membrane lipid metabolism.

Amino acid metabolomic analysis involved in flavor quality and cold tolerance in peach fruit treated with exogenous glycine betaine

Glycine betaine (GB) has been reported to mitigate chilling injury of peach fruit during postharvest cold storage, but the effects of GB treatment on changes of fruit flavor and amino acid metabolism remain unclear. In this study, the changes of organic acids and amino acids in peach fruit treated with GB were analyzed through physiological and metabolomic methods. The results manifested that GB treatment reduced internal browning index and maintained higher contents of total soluble solids, titratable acidity, organic acids and total free amino acids. Electronic tongue analysis exhibited separation between GB-treated and control fruit. Additionally, GB treatment increased proline, polyamines and γ-aminobutyric acid (GABA) contents by higher enzyme activities and upregulated gene expressions of arginine metabolism, GABA shunt pathway and lower enzyme activities and downregulated gene expressions of polyamine degradation pathway. Thus, GB treatment could enhance flavor quality and cold tolerance of peach fruit during low temperature storage.

Transcriptome and DNA methylome analysis reveal new insights into methyl jasmonate-alleviated chilling injury of peach fruit after cold storage

Methyl jasmonate (MeJA) has been used to alleviate the chilling injury (CI) caused by postharvest cold storage of horticultural crops involving peach fruit. However, the molecular mechanism remains largely unknown. Here, we treated melting peach fruit (Prunus persica L. Batsch., cv. Hujingmilu) with different concentrations of MeJA, followed by storage at 0 °C up to 28 d. Peach fruit treated with 1 mM MeJA delayed the development of CI during 3 d shelf-life followed by 28 d cold after storage (C28dS3). The alleviated CI was associated with significant higher content of JA-Ile in peach fruit after MeJA treatment than controls. RNA-Seq revealed significant alternations in expression of genes related to ethylene synthesis, fruit softening, flesh browning and aroma-related volatile synthesis. Transcription factors associated with fruit ripening such as PpNAC1 and JA signaling such as PpMYC2.2 showed higher transcript levels in MeJA treated peach fruit than controls. Peach fruit with CI symptom had higher genome methylation level than MeJA treated fruit after cold storage at C28dS3. Reverse patterns between transcript abundance and DNA methylation in promoter were observed for transcription factor PpNAC1 and downstream PpACS1 for ethylene synthesis, PpExp1 for softening, and PpAAT1 for volatile ester and lactone production. Overall, in addition to providing new insights into the regulatory mechanism for MeJA in alleviating fruit chilling injury through integration of transcriptome and DNA methylome, our study also establishes a foundation for fruit quality maintaining after cold storage of peach fruit.

Short-term hypobaric treatment alleviates chilling injury by regulating membrane fatty acids metabolism in peach fruit.

Short-term hypobaric treatment (SHT) on postharvest quality and membrane fatty acids metabolism were studied in peach fruit (Prunus persica [L.] Batsch., cv. Feicheng) during shelf life after cold storage. SHT was effective in alleviating chilling injury (CI) and maintaining postharvest quality. SHT reduced the production of malondialdehyde (MDA) and electrolyte leakage (EL), and increased membrane fluidity. In addition, SHT plays an imperative role in reducing saturated fatty acid (SFA), increasing unsaturated fatty acid (USFA), and keeping a higher unsaturation level in peach fruit. Meanwhile, SHT enhanced the activity of fatty acid synthetase (FAS), upregulated the expression levels of FAD2, FAD3-1, FAD3-2, and FAD7 genes at the early stage of storage, as well as inhibited the activity of lipoxygenase (LOX) and gene expression of LOX1. These results suggested that SHT could increase fatty acids unsaturation by regulating FAS activity, FAD and LOX1 gene expression, thus maintain high membrane stability and alleviate CI. PRACTICAL APPLICATIONS: CI is an important factor affecting the postharvest quality of peaches in cold storage, and metabolism of membrane fatty acids is one of the main CI response mechanisms. Our previous study has shown that SHT could alleviate CI in peach fruit. Therefore, it is of great significance to investigate the regulation of membrane fatty acids metabolism under SHT. Results from this study suggest that the enhancement of chilling tolerance by SHT in peaches could be explained, at least in part, as being due to enhanced FAS activity, upregulated the expression of FAD gene, and inhibited LOX1 to maintain higher unsaturation level. All in all, we explored the response mechanism of membrane fatty acids metabolism under SHT in peach fruit, and supplied theoretical guidance for application of the technology.

Transcriptome and genome analysis to identify C2H2 genes participating in low-temperature conditioning-alleviated postharvest chilling injury of peach fruit

Abstract Objectives This work intended to identify candidate C2H2 genes participating in low-temperature conditioning (LTC)-alleviated postharvest chilling injury of peach fruit. Materials and Methods For LTC treatment, fruit were pre-stored at 10 °C for 5 d and then transferred to 0 °C storage. Fruit firmness was measured by a hardness tester. H2O2 content was determined by luminosity measurement model using a multifunctional enzyme labeler. Identification of C2H2 family members was performed by HMMSCAN according to peach genome. The cis-acting element of gene promoters was analyzed using the Plant CARE website. Weighted gene coexpression network analysis (WGCNA) was performed by the WGCNA package in the BMK Cloud platform. Results LTC treatment decreased flesh browning rate and H2O2 production of ‘Beijing No. 9’ peach. Transcription factor identification of differentially expressed genes in 0 °C and the LTC treatment indicated that peach C2H2 participated in the regulation of chilling injury. A total of 47 C2H2 genes were identified based on peach genome. Real-time quantitative polymerase chain reaction (qRT-PCR), phylogenetic analysis and promoter cis-acting element analysis revealed that ZFP21 was involved in the regulation of LTC-alleviated chilling injury in peach. WGCNA and dual luciferase assay suggested that ZFP21 participated in LTC-alleviated chilling injury by downregulating the expression of reactive oxygen species-related genes Rboh. Conclusions Our investigation, based on genome and RNA-seq, revealed that ZFP21 was involved in LTC treatment-alleviated chilling injury of peach fruit. This work is useful for the identification of peach cold tolerance-related genes and the study of C2H2 family in peach.

Cold shock treatment alleviates chilling injury in peach fruit by regulating antioxidant capacity and membrane lipid metabolism

Abstract Objectives The work intended to reveal the effect of cold shock (CS) treatment on chilling injury (CI), antioxidant capacity, and membrane fatty acid of peach fruit. Materials and methods Peaches were soaked in ice water (0 °C) for 10 min and stored at 5 °C for 28 days for determination, except CI, and then stored for 3 days at 20 °C, only CI was measured. The electrolyte leakage (EL) was measured by conductivity meter. The activities of antioxidant enzymes (superoxide dismutase, ascorbate peroxidase, catalase, and peroxidase) and key enzymes of membrane lipid metabolism (phospholipase D, lipase, and lipoxygenase) as well as reactive oxygen species (ROS; O2·– and H2O2) were measured with a spectrophotometer. An ELISA kit and gas chromatography were used to determine membrane lipids and membrane fatty acids. The relative gene expression was measured by real-time polymerase chain reaction analysis. Results The results showed that CS treatment effectively delayed CI, suppressed the increase of EL and malondialdehyde content. Meanwhile, CS-treated fruit exhibited lower level of ROS and higher activities of antioxidant enzymes. Furthermore, CS treatment inhibited the activities as well as the relative gene expression of key enzymes in membrane lipid metabolism. CS-treated fruits maintained higher membrane fatty acid unsaturation and lower phosphatidic acid content. Conclusions These results indicated that CS treatment effectively alleviated CI and maintained the integrity of cell membranes by inducing antioxidant-related enzyme activity and maintaining a higher ratio of unsaturated fatty acids to saturated fatty acids.

Postharvest Treatment of ‘Florida Prince’ Peaches with a Calcium Nanoparticle–Ascorbic Acid Mixture during Cold Storage and Its Effect on Antioxidant Enzyme Activities

Chilling injury (CI) is a physiological disorder resulting from low storage temperatures that affects the fruit quality and marketing of the ‘Florida Prince’ peach. In this study, the exogenous application of a mixture of calcium nanoparticles (CaNPs) and ascorbic acid was found to significantly alleviate the symptoms of CI in peaches during cold storage. Fruits were treated with CaNPs plus different concentrations of ascorbic acid (AA; 0, 3, 6, and 9 mM). Peaches were immersed in CaNP–AA for 15 min before being stored at 4 ± 1 °C and 95 ± 1% RH for 30 days. We observed that the 9 mM CaNP–AA treatment lowered the values for the CI index, ion leakage, and malondialdehyde (MDA) content and increased antioxidant enzyme activities (AEAs), such as for ascorbate oxidase (APX), catalase (CAT), superoxide dismutase (SOD), and glutathione reductase (GR). Furthermore, the treatment reduced the accumulation of both H2O2 and O2•− and increased the level of DPPH reduction throughout the duration of cold storage. Our results suggest that 9 mM CaNP–AA treatment suppresses the incidence of CI in peach fruit throughout cold storage, possibly because 9 mM CaNP–AA is at least partly involved in enhancing the antioxidant system via its effect on antioxidant substances. The results indicate that applying the 9 mM CaNP–AA treatment afforded peaches with enhanced tolerance against cold storage stress.

DNA hypermethylation associated with the development of temperature-dependent postharvest chilling injury in peach fruit

Peach fruit is often subjected to postharvest chilling injury (CI) during long-term cold storage and the degree of CI is related to the storage temperature. Analysis of the data on softening, ethylene production and internal browning (IB) showed that CI occurred in fruit stored at or below 12 °C. Impairment of ethylene production and softening was greater in fruit stored at 0 and 5 °C and was consistent with lower expression of related critical genes. Lower malondialdehyde and hydrogen peroxide contents and enhanced hydroxyl radical contents were observed in fruit stored at 0 and 5 °C. These changes were associated with higher transcript levels of polyphenol oxidases and peroxidase, but lower expression levels of lipoxygenase, superoxide dismutase and catalase. To investigate whether DNA methylation is involved in the CI development in peach fruit, single-base resolution DNA methylome and transcriptome analysis was carried out. The DNA methylation level was higher in CI fruit and a close positive correlation was observed between the methylation level and IB index. Furthermore, for most genes involved in softening, ethylene biosynthesis and signal transduction, IB and reactive oxygen species metabolism, the expression level was found to be well correlated with low temperature-induced DNA hyper- or hypo-methylation in promoter, genebody or downstream regions. It was concluded that changes in DNA methylation in different genomic regions regulate CI associated gene expression and contribute to the development of temperature-dependent CI in postharvest peach fruit.

Genome-wide identification of heat shock transcription factors and potential role in regulation of antioxidant response under hot water and glycine betaine treatments in cold-stored peaches.

Heat shock transcription factors (Hsfs) play pivotal roles in plant responses to stress. Although glycine betaine (GB) and hot water (HW) treatments are effective in reducing chilling injury (CI), little is known about the characterization of the Hsfs gene family and its potential roles in alleviating CI by regulating antioxidant systems in peach fruit. In this study, 17 PpHsfs were identified in the peach genome and were investigated using bioinformatics, including chromosomal locations, phylogenetic relationships, gene structure, motifs, and promoter analyses. The expression patterns of PpHsfs under GB and HW treatments were also investigated. The PpHsfs showed different expression patterns in GB- and HW-treated fruit, and most of them were significantly up-regulated by both treatments, especially PpHsfA1a/b, PpHsfA2a, PpHsfA9a, and PpHsfB2a/b. Meanwhile, GB and HW treatments induced higher levels of gene expression and antioxidant enzyme activity of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) compared to the control, contributing to the inhibition of hydrogen peroxide (H2 O2 ) accumulation and superoxide anion (O2 .- ) production. Moreover, the correlation analysis between PpHsfs and antioxidant-related genes showed that three PpAPXs were significantly correlated with ten PpHsfs, whereas PpCAT and PpSOD had no significant correlations with PpHsfs, which indicated that PpAPX might be regulated by PpHsfs. The results indicated that GB and HW treatments induced different PpHsfs transcript levels to regulate the antioxidant gene expressions, which might be beneficial in inhibiting the accumulation of reactive oxygen species and protecting the integrity of cell structure, thus alleviating the development of CI in peach fruit during cold storage. © 2021 Society of Chemical Industry.

Salicylic acid treatment mitigates chilling injury in peach fruit by regulation of sucrose metabolism and soluble sugar content

Peach fruit stored in the cold are susceptible to chilling injury. A pre-storage treatment with the natural hormone salicylic acid can alleviate chilling damage, although the mechanism is unclear. We found that a treatment with 1 μmol L−1 salicylic acid for 15 min prior to storage at 4 °C delayed and reduced fruit internal browning, a symptom of chilling injury. Salicylic acid had a large effect on sugar metabolism, increasing total soluble sugars via a substantial increase in sucrose content. The transcript abundance of genes related to sucrose biosynthesis and degradation was significantly regulated by salicylic acid, consistent with the changes in sucrose content. Salicylic acid treatment also increased the expression of two DREB cold stress-related proteins, transcriptional activators that regulate cold resistance pathways. The results show that salicylic acid alleviates chilling injury in peach by multiple mechanisms, including an increased content of sucrose and activation of cold response genes.

Jasmonic acid and salicylic acid induce the accumulation of sucrose and increase resistance to chilling injury in peach fruit.

Salicylic acid (SA) and jasmonic acid (JA) can both enhance resistance of chilling injury (CI) in cold-storage peach fruit, but the regulatory mechanisms involved and whether there is a coordinated regulation between them is unclear. In this study, postharvest peach fruit were treated with an aqueous SA solution for 15 min or an aqueous JA solution for 30 s before storage at 4°C for 35 days. SA and JA treatments both delayed and reduced development of internal browning (a symptom of CI) and induced the accumulation of hydrogen peroxide and sucrose. The SA and JA also reduced catalase and peroxidase activities, which are involved in hydrogen peroxide generation. The SA and JA treatments significantly regulated the transcript abundance of genes related to sucrose biosynthesis and degradation consistent with the observed increase in sucrose content. These results intimate that JA and SA may be involved in coordinating the alleviation of CI via increased accumulation of sucrose. © 2021 Society of Chemical Industry.

Genome-wide identification of phospholipase C related to chilling injury in peach fruit

Phospholipase C (PLC) responsible for acyl editing of phospholipids plays crucial roles in chilling sensitive plants and flesh fruit, which is prone to physiological disorders caused by chilling stress, collectively termed chilling injury. Up to now, genes encoding PLC in Prunus persica genome (PpPLC) and characteristics closely related to chilling injury remain elusive. In this study, a total of 10 PpPLCs were identified and divided into two subclasses, with equal number of phosphatidylinositol-specific PLC (PpPI-PLCs) and non-specific PLC (PpNPCs). Compared with PpNPCs, PpPI-PLCs show the differences in the number and the organization of exons and introns, as well as multiple splice variants. Meanwhile, the subclasses share two motifs enriched with lysine and proline. Furthermore, the PpPLCs consistently displayed two distinct transcriptional responses to four treatments conferring chilling tolerance in peach fruit, with the upregulation of PpPI-PLCs such as PpPI-PLC4.1/4.2 and the down-regulation of PpNPCs except to PpNPC1, which is located at the plasma membrane. The results will facilitate deciphering the functions of the PLC in plants and flesh fruit when they undergo chilling injury.

Jasmonic acid treatment alleviates chilling injury in peach fruit by promoting sugar and ethylene metabolism

Peach (Prunus persica L.) fruit are highly susceptible to chilling injury during cold storage, resulting in internal flesh browning and a failure to soften normally. We have examined the effect of a postharvest treatment consisting of a brief (30 s) dip in the natural plant hormone jasmonic acid, prior to storage at 4 °C. Jasmonic acid treatment reduced the severity of internal flesh browning and did not inhibit fruit softening over a 35 d storage period. Two major physiological effects of jasmonic acid on the fruit were observed, an increase in ethylene production and a prevention of the decline in soluble sugar content seen in controls. An increased soluble sugar content may have multiple benefits in resisting chilling stress, scavenging reactive oxygen species and acting to stabilize membranes. Our results show that a treatment with jasmonic acid can enhance chilling tolerance of peach fruit by regulating ethylene and sugar metabolism.

Interaction between nitric oxide and storage temperature on sphingolipid metabolism of postharvest peach fruit

Both nitric oxide (NO) and cold storage have positive effects on the maintenance of fruit quality during storage. However, the roles of NO and storage temperatures in regulating the responses of sphingolipids metabolism to chilling injury of peach fruit during storage remain unknown. Peaches were treated by immersion in distilled water and 15 μmol L−1 NO solution, then stored at 25 °C and 0 °C, respectively. The effects of NO-treatment and storage temperature on the activities of enzymes in sphingolipid metabolism and the contents of sphingolipids in peach fruits were studied. NO maintained higher activities of acid phosphatase (AP) and alkaline phosphatase (ALP) in peach fruits at 25 °C, but promoted the decrease in the activities of AP and ALP at 0 °C, suggesting the regulation by NO on AP and ALP could be modulated by temperature. Compared with the storage at 25 °C, cold storage at 0 °C decreased the activities of phospholipase A (PLA), alkaline phosphatase (ALP), 3-ketodihydrosphingosine reductase (KDSR), sphingosine kinase (SPHK), ceramide synthase (CERS), ceramide kinase (CERK), and the contents of sphingosine (SPH), ceramide (CER), sphingosine-1-phosphate (S1P), ceramide-1-phosphate (C1P), sphingomyelin (SM), and increased the activities of phospholipase C (PLC), phospholipase D (PLD), sphingomyelin synthase (SMS). NO significantly increased the contents of sphingolipid metabolites, and the activities of PLA, KDSR, SPHK, CERS, CERK, but decreased the activities of PLC, PLD, SMS of peaches. The results suggested that NO could maintain sphingolipid metabolism to relieve the response of the postharvest fruit to low temperature.

Combination of Low Fluctuation of Temperature with TiO2 Photocatalytic/Ozone for the Quality Maintenance of Postharvest Peach.

Chilling injury, tissue browning, and fungal infection are the major problems of peach fruit during post-harvest storage. In this study, a precise temperature control cold storage with low-temperature fluctuation (LFT) and internal circulation flow system is designed. An ozone (O3) generator and a (titanium dioxide) TiO2 photocatalytic reactor were applied to cold storage to investigate the variation of LFT combined with ozone fumigation and a TiO2 photocatalytic reactor in the efficiency of delaying ripening and maintaining peach fruit quality. Results showed that the temperature fluctuation with the improved control system was only ±0.1 to ±0.2 °C compared with that of ±0.5 to ±1.0 °C in conventional cold storage. LFT significantly reduced the chilling injury of peach fruit during storage. Although LFT combined with fumigation of 200 mg m−3 ozone periodical treatment slightly damaged the peach fruit after 40 d of storage, its combination with the TiO2 photocatalytic system significantly improved the postharvest storage quality of the fruit. This treatment maintained higher titratable acidity (TA), total soluble solids (TSS), better firmness, color, microstructure, and lower decay rate, polyphenol oxidase (PPO) activities, total phenol accumulation, respiratory intensity, ethylene production, and malondialdehyde (MDA) content during 60 d of storage. All the results show that LFT combined with the TiO2 photocatalytic system might be a promising technology for quality preservation in peach fruit storage.

Methyl Jasmonate Promotes Phospholipid Remodeling and Jasmonic Acid Signaling To Alleviate Chilling Injury in Peach Fruit.

Chilling injury (CI) is a physiological disorder induced by cold, which heavily limit crop production and postharvest preservation worldwide. Methyl jasmonate (MeJA) can alleviate CI in various fruit species, including peach; however, the underlying molecular mechanism is poorly understood. Here, changes in contents of phenolics, lipids, and jasmonic acid (JA) and gene expressions are compared between MeJA and control fruit. Exogenous MeJA inhibited expressions of PpPAL1, PpPPO1, and PpPOD1/2 but did not affect the phenolic content. Furthermore, MeJA fruit showed lower relative electrolyte leakage, indicating less membrane damage. Meanwhile, the enrichment of linoleic acid in the potential lipid biomarkers, especially phosphatidylcholine, phosphatidylethanolamine, and phosphatidylglycerol, coincided with lower expressions of PpFAD8.1 but higher PpLOX3.1 and JA content. In the JA signaling pathway, MeJA significantly upregulated expressions of PpMYC2.2 and PpCBF3 but downregulated PpMYC2.1. In conclusion, adjustments of fatty acids in phospholipids contribute to MeJA-induced alleviation of CI in peach fruit via induction of the JA-mediated C-repeat-binding factor pathway.

Effects of Putrescine Application on Peach Fruit during Storage

The peach industry faces serious economic losses because of the short “green” life of the fruit at postharvest. In the present study, we investigated the effects of putrescine (PUT) application on the quality characteristics, pattern of ripening, storage behaviour and shelf life of peach fruit during low-temperature storage. The aqueous solution of PUT (0, 1, 2 and 3 mM) was applied to the peach trees at three distinctive stages of fruit growth and development. The fruits, harvested at the commercial stage of maturity, were stored at 1 ± 1 °C and 90 ± 2% relative humidity for 6 weeks. The data for fruit firmness, total soluble solids (SSC), titratable acidity (TA), ascorbic acid (AsA) content, rate of ethylene production, chilling injury (CI) index and colour perception were collected at harvest and then on a weekly basis throughout the storage period. The results showed that spray application of PUT significantly reduced the incidence of CI and reduced the rates of fruit softening, loss in fruit weight, SSC, TA, AsA content and fading of skin colour during storage, regardless of the doses of PUT applied, or the time of application. However, the positive effects on the quality characteristics of peach fruit, including CI, were more pronounced with the higher doses of PUT, specifically when applied at 2 mM. In conclusion, CI in peach fruit may be substantially alleviated by the spray application of 1–3 mM PUT during fruit growth without compromising the quality of the fruit for up to 6 weeks in low-temperature storage.

Glycine betaine reduces chilling injury in peach fruit by enhancing phenolic and sugar metabolisms

Glycine betaine (GB) treatment is useful to reduce chilling injury (CI) of several kinds of fruits including peach. However, the regulatory mechanism remains unknown. In this study, peach fruit was treated with 10 mmol L−1 GB solution for 10 min. The effects of GB treatment on CI, phenolic and soluble sugar metabolism were investigated in this study. Moreover, phenylpropanoid and soluble sugar content, and enzyme activities associated with phenolic and sugar metabolisms were also measured. The results showed that GB reduced CI and maintained high levels of total phenolic and flavonoid content. The activities of phenylpropanoid metabolism-related enzymes were significantly enhanced by GB. Higher content of sucrose and lower contents of fructose and glucose were observed in GB-treated fruits. Therefore, our results showed that GB could enhance chilling tolerance of peach through regulating phenolic and sugar metabolisms, and maintaining high levels of individual phenolic and sucrose content.

Melatonin treatment reduces chilling injury in peach fruit through its regulation of membrane fatty acid contents and phenolic metabolism

Effects of 0.1 mM melatonin (MT) on chilling injury (CI), membrane fatty acid content and phenolic metabolism in peach fruit were studied during storage at 1°C for 28 days. MT treatment delayed the development of CI in peach fruit, as was illustrated by MT-treated fruit showing lower CI incidence, CI index and firmness loss than the control. MT treatment prevented membrane lipid peroxidation and contributed to maintaining a higher ratio of unsaturated to saturated fatty acids in peach fruit. MT treatment also stimulated the activities of glucose-6-phosphate dehydrogenase, shikimate dehydrogenase and phenylalanine ammonia lyase, but inhibited the activities of polyphenol oxidase and peroxidase. This would help in activating the accumulation of total phenolic and endogenous salicylic acid that might have a direct function in alleviation of CI. These results indicate that MT treatment can be an effective technique to reduce postharvest CI during low temperature storage of peach fruit.

Transcriptomic and metabolic analyses provide new insights into chilling injury in peach fruit.

Low temperature conditioning (LTC) alleviates peach fruit chilling injury but the underlying molecular basis is poorly understood. Here, changes in transcriptome, ethylene production, flesh softening, internal browning and membrane lipids were compared in fruit maintained in constant 0°C and LTC (pre-storage at 8°C for 5d before storage at 0°C). Low temperature conditioning resulted in a higher rate of ethylene production and a more rapid flesh softening as a result of higher expression of ethylene biosynthetic genes and a series of cell wall hydrolases. Reduced internal browning of fruit was observed in LTC, with lower transcript levels of polyphenol oxidase and peroxidase, but higher lipoxygenase. Low temperature conditioning fruit also showed enhanced fatty acid content, increased desaturation, higher levels of phospholipids and a preferential biosynthesis of glucosylceramide. Genes encoding cell wall hydrolases and lipid metabolism enzymes were coexpressed with differentially expressed ethylene response factors (ERFs) and contained ERF binding elements in their promoters. In conclusion, LTC is a special case of cold acclimation which increases ethylene production and, operating through ERFs, promotes both softening and changes in lipid composition and desaturation, which may modulate membrane stability, reducing browning and contributing to alleviation of peach fruit chilling injury.