Low-temperature Conditioning Treatment Research Articles

Identification of COR413 Gene Family in Peach and Its Expression in Low Temperature and LTC Treatment at Postharvest

Peach were susceptible to chilling injury during low temperature (0 o C) storage at postharvest, and LTC (Low temperature conditioning) treatment could reduce chilling injury such as of H 2 O 2  production and fruit browning. In order to study the function of peach COR413  in the regulation of postharvest chilling injury in peach ‘Beijing No. 9’, four COR413 gene family members were identified based on the peach genome database, namely  PpCOR1 ~ PpCOR4 . Phylogenetic analysis showed that the four PpCORs could be clustered into two subfamilies. PpCOR1 ~ PpCOR3  belonged to the first subfamily, and most of the members in this subfamily were located in plasma membrane. PpCOR4  belongs to the second subfamily, and its members are mainly located in thylakoid membrane. The cis-acting elements analysis of PpCORs  promoter showed that PpCOR3  contained abundant abiotic stress responsive and hormone responsive elements such as jasmonate and abscisic acid. The results of gene expression showed that PpCOR3 was induced by low temperature while LTC treatment could repress the induction of PpCOR3  by low temperature. Interestingly, the expression of PpCOR3  was positively correlated with the change of H 2 O 2  content in peach, which indicated that PpCOR 3 was involved in the regulation of postharvest chilling injury in peach fruit. This result provides a theoretical basis for the study of postharvest storage and quality maintenance of peach fruit as well as the breeding of cold resistant peach varieties.

Low Temperature Conditioning Reduced the Chilling Injury by Regulating Expression of the Dehydrin Genes in Postharvest Huangguan Pear (Pyrus bretschneideri Rehd. cv. Huangguan)

‘Huangguan’ pear (Pyrus bretschneideri Rehd. cv. Huangguan) fruit is sensitive to chilling injury (CI), which exhibits peel browning spots (PBS) during cold storage. Dehydrin (DHN) is considered to be related to cold tolerance in plants, but its function in postharvest pear fruit during storage remains unclear. In this study, six PbDHNs (PbDHN1–6) genes were identified and characterized, and the PbDHN proteins were sorted into YnKn, SKn and YnSKn according to the major conserved motifs related to the number and location of K-segments, S-segments, and Y-segments. In addition, there were five cold-responsive related cis-acting elements in the promoter region of the PbDHNs. The analysis of fruit quality suggested that compared with a storage temperature at 20 °C, a storage temperature of 0 °C results in CI in ‘Huangguan’ pear fruit, while a storage temperature of 10 °C and low temperature conditioning (LTC) alleviates the CI. Moreover, gene expression results indicated that the six PbDHNs were markedly enhanced at low temperatures, especially at 0 °C. The transcripts of PbDHN1, PbDHN4, PbDHN5 and PbDHN6 were also increased in the fruit stored at 10 °C, but they were lower than that at 0 °C except PbDHN5. Compared with low temperature storage at 0 °C, LTC treatment significantly depressed the expression of PbDHN1, PbDHN2, PbDHN3, PbDHN4, and PbDHN6, while enhanced the mRNA amount of PbDHN5. In conclusion, PbDHN1, PbDHN4, PbDHN5, and PbDHN6 were closely related to the CI, and LTC lowered the CI by down-regulating the expression of PbDHN1, PbDHN4, and PbDHN6 and by up-regulating PbDHN5 in ‘Huangguan’ pear fruit.

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.

Arachidonic acid treatment combined with low temperature conditioning mitigates chilling injury in cold‐stored banana fruit

SummaryCold‐stored banana fruit is particularly susceptible to chilling injury (CI). Over transportation and storage, CI is a key physiological factor affecting postharvest banana quality. Arachidonic acid (ARA) is considered a signal molecule that elicits stress signalling networks in plants. However, whether exogenous ARA treatment can reduce CI in postharvest fruit remains unknown. This study investigated the effects of a combination of exogenous ARA treatment and low temperature conditioning (LTC) on mitigating CI occurrence. ARA + LTC treatment decreased electrolyte leakage, accumulation of malondialdehyde, H2O2 content, weight loss and occurrence of CI symptoms. This treatment also delayed fruit softening and colour development, and maintained both vitamin C and chlorophyll contents in bananas stored at 0 °C for 36 days. In addition, ARA + LTC treatment significantly increased the activities of ascorbate peroxidase, glutathione reductase, peroxidase, catalase and superoxide dismutase. Concluding, ARA + LTC treatment has the potential to reduce CI in banana fruit during cold storage. This makes it an effective postharvest technique for fruits and vegetables susceptible to CI.

Role of AOX in low-temperature conditioning induced chilling tolerance in sweetpotato roots

Chilling injury is a significant postharvest physiological disorder in sweetpotatoes during storage. This study investigated the role of alternative oxidase (AOX) in low-temperature conditioning (LTC) induced chilling tolerance in sweetpotato storage roots. Roots were pre-treated with a LTC treatment (12°C for 5 days) or with salicylhydroxamic acid (SHAM, AOX inhibitor) combined with LTC, followed by storage at 4°C for 35 days. Results showed that LTC pre-treatment significantly lowered root chilling injury symptoms, suppressed malondialdehyde levels and the accumulation of reactive oxygen species. However, SHAM reduced the impact triggered by LTC and resulted in lower antioxidant enzyme activities and free proline content, reduced glutathione and adenosine triphosphate contents compared with LTC alone. The results from gene expression analysis showed that LTC-induced higher transcript level of IbAOX1a and IbAOX1b during storage at 4°C. However, SHAM suppressed the effect of LTC. SHAM treatment not only reduced AOX activity but also resulted in a lower AOX transcript and protein abundance, which might contribute to the lower AOX activity observed in the SHAM treated roots. These results suggest that AOX participates in LTC-induced chilling tolerance of sweetpotato storage roots.

ETHYLENE RESPONSE FACTOR39-MYB8 complex regulates low-temperature-induced lignification of loquat fruit.

Flesh lignification is a specific chilling response that causes deterioration in the quality of stored red-fleshed loquat fruit (Eribotrya japonica) and is one aspect of wider chilling injury. APETALA2/ETHLENE RESPONSIVE FACTOR (AP2/ERF) transcription factors are important regulators of plant low-temperature responses and lignin biosynthesis. In this study, the expression and action of 27 AP2/ERF genes from the red-fleshed loquat cultivar ‘Luoyangqing’ were investigated in order to identify transcription factors regulating low-temperature-induced lignification. EjERF27, EjERF30, EjERF36, and EjERF39 were significantly induced by storage at 0 °C but inhibited by a low-temperature conditioning treatment (pre-storage at 5 °C for 6 days before storage at 0 °C, which reduces low-temperature-induced lignification), and their transcript levels positively correlated with flesh lignification. A dual-luciferase assay indicated that EjERF39 could transactivate the promoter of the lignin biosynthetic gene Ej4CL1, and an electrophoretic mobility shift assay confirmed that EjERF39 recognizes the DRE element in the promoter region of Ej4CL1. Furthermore, the combination of EjERF39 and the previously characterized EjMYB8 synergistically transactivated the Ej4CL1 promoter, and both transcription factors showed expression patterns correlated with lignification in postharvest treatments and red-fleshed ‘Luoyangqing’ and white-fleshed ‘Ninghaibai’ cultivars with different lignification responses. Bimolecular fluorescence complementation and luciferase complementation imaging assays confirmed direct protein–protein interaction between EjERF39 and EjMYB8. These data indicate that EjERF39 is a novel cold-responsive transcriptional activator of Ej4CL1 that forms a synergistic activator complex with EjMYB8 and contributes to loquat fruit lignification at low temperatures.

Evaluation of 1-methylcyclopropene (1-MCP) and low temperature conditioning (LTC) to control brown of Huangguan pears

Harvested ‘Huangguan’ pears are popular with consumers, but a series of physiological diseases are likely to occur in Huangguan pears during storage, especially brown. The objective of the study was to evaluate the effectiveness of 1-methylcyclopropene (1-MCP) and low temperature conditioning (LTC) on the control of brown in Huangguan pears. Physiological indexes and enzyme activity including browning index, total phenol content, malondialdehyde (MDA) content, electrolyte leakage, hydrogen peroxide (H2O2) content, superoxide radical (O2−) production rate, flavonoid content, soluble solid content (SSC), l-ascorbate peroxidase (APX), phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) were measured. Results showed that 1-MCP or LTC treatment suppressed browning index, MDA content, electrolyte leakage, H2O2 content, O2− production rate, PPO activity and improved total phenol content, flavonoid content, SSC, APX and PAL activity in comparison with the control. Furthermore, the combination of 1-MCP and LTC contributed the maximum efficacy compared to the individual treatment. In conclusion, our results indicated the combined treatment may be an efficient way to control brown in Huangguan pears.

Low temperature conditioning alleviates loss of aroma-related esters of ‘Nanguo’ pears by regulation of ethylene signal transduction

The optimum harvest time for ‘Nanguo’ pears lasts for only 20 days. Refrigeration is a common technique used to extend the fruit supply. However, with low-temperature storage, the proper aroma of the pear is lost when it matures during shelf-life at room temperature. In this study, we investigated the ability of low-temperature conditioning (LTC) to regulate aroma esters of ‘Nanguo’ pears, and identified the key genes in the ethylene signal transduction pathway based on RNA-seq analysis. LTC caused higher ethylene production and effectively alleviated the loss of aroma-related esters in ‘Nanguo’ pears during refrigeration and during the subsequent shelf-life at room temperature. Furthermore, the expression levels of PuERS1, PuEIN4, PuEIN2, and PuERF were increased under LTC treatment. Thus, we speculate that the alleviation effect of LTC on fruit aroma esters is closely related to ethylene signal transduction, including up-regulated expression of PuERS1, PuEIN4, PuEIN2, and PuERF.

Effects of low‐temperature conditioning and cold storage on development of chilling injuries and the transcriptome of ‘Wonderful’ pomegranate fruit

SummaryWe recently developed a postharvest low‐temperature‐conditioning (LTC) treatment for ‘Wonderful’ pomegranate fruits that involve prestorage exposure to 15 °C for 10 days, and it markedly enhanced chilling tolerance. To elucidate the molecular mechanisms involved in the fruit responses to LTC, we conducted RNA‐Seq analysis of ‘Wonderful’ pomegranate inner membrane tissue at four different time points: (i) immediately after harvest; (ii) after the LTC treatment; (iii) after 2 weeks of cold storage at 1 °C; and (iv) after LTC + 2 weeks at 1 °C. Pairwise comparisons revealed that 7798 transcripts were significantly (P ≤ 0.05) induced or repressed by a factor of at least four in the chilling treatment (2422 upregulated and 5376 downregulated) as compared with just 1997 transcripts in the LTC + chilling treatment (974 upregulated and 1023 downregulated). Thus, application of LTC mitigated the overall changes in transcript levels associated with cold storage. Furthermore, the LTC + chilling affected gene expression patterns related to regulatory and stress mechanisms, including modification of specific transcription factor, signalling and stress‐related genes.

Low-temperature conditioning combined with cold storage inducing rapid sweetening of sweetpotato tuberous roots (Ipomoea batatas (L.) Lam) while inhibiting chilling injury

Sweetpotato tuberous roots (Ipomoea batatas (L.) Lam) are prone to chilling injury (CI) when stored at low temperature. Here, tuberous roots were subjected to low-temperature conditioning (LTC) at 10 °C for 5 d before exposure to chilling stress under cold storage at 4 °C for 28 d. After investigation of antioxidant and sugar metabolic responses to chilling stress, the results indicated that LTC treatment can enhance sweetness while effectively reducing CI observed in roots stored at 4 °C for 28 d. Moreover, LTC triggered increased sucrose levels, transcription of enzyme genes, and increased superoxide dismutase, catalase, and ascorbate peroxidase activities, while preventing increases in malondialdehyde content, relative leakage, and production of reactive oxygen species during cold storage. Furthermore, LTC may trigger beta-amylase gene transcription via C-repeat binding factor (CBF) pathway induction. Therefore, LTC combined with cold storage can induce fast sweetening in tuberous roots while preventing chilling injury.

Effects of low temperature conditioning on fruit quality and peel browning spot in ‘Huangguan’ pears during cold storage

‘Huangguan’ pears are susceptible to peel browning spots (PBS) during cold storage. In this study, the effects of low temperature conditioning (LTC) on fruit firmness, soluble solids content (SSC) and PBS incidence in ‘Huangguan’ pears were investigated. Fruit were directly stored at 0°C (control) and conditioned at 10°C for 3 d (LTC), respectively. Afterwards, all fruit were stored at 0°C. Fruit firmness was unaffected by the LTC treatment. However, SSC was higher in the LTC-treated fruit than in control fruit on days 30 and 60. Compared with the control, LTC treatment effectively inhibited the development of PBS, reduced the activities of lipoxygenase (LOX) and polyphenol oxidase (PPO), reduced malondialdehyde (MDA) content in peel tissue, the decline in the phenolic content, and it showed higher proline content before the appearance of PBS. In addition, LTC treatment decreased the expression levels of LOX1, PPO1 and PPO5 genes, while it up-regulated the expression of the PPO4 gene in peel tissue. These results indicate that the alleviation effect of LTC on the development of PBS was closely related to reduced membrane lipid peroxidation, activities of LOX and PPO, and the expression of LOX1, PPO1 and PPO5 genes in peel tissue in ‘Huangguan’ pears.

Low temperature conditioning alleviates peel browning by modulating energy and lipid metabolisms of ‘Nanguo’ pears during shelf life after cold storage

Refrigeration is a common technique for impeding the postharvest ripening of the ‘Nanguo’ pear (Pyrus ussuriensis Maxim.). However, peel of pears gradually become brown when the fruit are returned to room temperature after cold storage. Low temperature conditioning (LTC), in which fruit were initially stored at 10°C and then cooled during a 20 day period, delayed the incidence of peel browning (PB) of pears in our study. LTC-treated fruit showed a decrease in the content of malondialdehyde (MDA) and the relative leakage rate of the peel. The ATP content and energy charge (EC) were higher in LTC-treated pears. Gene expression levels of transcripts for NADH dehydrogenase (NDA), ATP synthase (ATPase) and vacuolar proton-inorganic pyrophosphatase (VPP), which were involved in oxidative phosphorylation, were all up-regulated by LTC treatment. Gene expression levels of phospholipase D (PLD) involved in glycerophospholipid metabolism were lower in LTC-treated fruit during the shelf-life. These results indicate that LTC treatment can effectively alleviate the PB of ‘Nanguo’ pear and the possible mechanisms are discussed.

Involvement of PAL, C4H, and 4CL in Chilling Injury-induced Flesh Lignification of Loquat Fruit

Loquat (Eriobotrya japonica) is a model fruit for investigating flesh lignification during storage and response to chilling injury. However, the investigations of enzymes and coding genes and loquat fruit lignification under low-temperature storage are still limited. Here, the activity and transcript levels of up-stream enzymes of the phenylpropanoid pathway, including l-phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), and 4-coumarate:coenzyme A ligase (4CL), were investigated. The results indicated that activity of these enzymes was positively correlated with loquat fruit lignification and suppression of these increases by heat treatment (HT) and low-temperature conditioning (LTC) significantly alleviated loquat fruit lignification. Coding genes for these enzymes were subsequently isolated based on information from an RNA-seq database and expression of Ej4CL1 was found to be the most responsive to low temperature and inhibition by HT and LTC treatment, whereas the other genes were less responsive to these treatments. Furthermore, function of Ej4CL1 was analyzed by transient overexpression in tobacco leaves, where it stimulated lignin accumulation. Ej4CL1 may be a key candidate that involved in CI-related loquat fruit lignification.

Effects of harvest date and low-temperature conditioning on chilling tolerance of ‘Wonderful’ pomegranate fruit

The optimal storage temperatures for ‘Wonderful’ pomegranates are between 5 and 7.5°C. However, application of a cold-quarantine disinfestation treatment against the Mediterranean fruit fly (Ceratitus capitate) requires exposure to a much lower temperature – below 1°C – for at least 14days; conditions that often cause chilling injury (CI) symptoms, manifested in surface pitting and internal browning of the white spongy tissue and inner membranes. We demonstrated that harvest time had a remarkable effect on fruit chilling tolerance: early-harvested fruits were very susceptible to CI and were severely damaged after 4 weeks of exposure to 1°C followed by an additional week at a shelf-life temperature of 20°C, whereas late-harvested fruits were rather chilling tolerant and showed hardly any CI symptoms after similar exposure. In addition, we developed a postharvest low-temperature-conditioning (LTC) treatment for ‘Wonderful’ pomegranate fruits; it involves exposure to a moderate temperature of 15°C for 10days before transfer to the cold-quarantine treatment. When this proposed LTC treatment was applied to mid-season fruits, it entirely prevented the appearance of CI symptoms after 4 weeks storage at 1°C followed by one additional week at 20°C, without impairment of fruit-quality parameters, as manifested in loss of weight, flavor, juice total soluble solids and acid contents, and total antioxidant activity. Overall, these findings demonstrate that harvesting mid- and, preferably, late-season fruits, and applying a pre-storage LTC treatment at 15°C for 10days, enables export of ‘Wonderful’ pomegranates to new markets that require cold-quarantine disinfestation treatments against the Mediterranean fruit fly.

Postharvest Low Temperature Conditioning Reduces Peel Browning and Improves Fruit Quality in Storage and Subsequent Shelf Life of Huangguan Pear

Huangguan pear (Pyrus bretschneideri Rehd cv. Huangguan) is a pear cultivar that rapidly developed in China. However, rapid postharvest browning appearing in fruit peel and core during storage and shelf life pose a challenge for their marketing. The potential for low temperature conditioning (LTC) treatment to inhibit peel browning and improve quality of Huangguan pears in storage and shelf life was investigated. Pears were treated at 8℃ - 9℃ for 1, 3, 6 and 9 d, respectively, physiological indexes, including peel and core browning, core breakdown, malondialdehyde (MDA) content and ethanol content were determined and quality in storage period and shelf life was evaluated in this paper. LTC treatment alleviated peel browning and core browning either in storage or shelf life remarkably; it also delayed the decline of firmness, total soluble solids and titratable acidity in storage to some extent, inhibited ethanol and MDA content both in storage and shelf life effectively and maintained juiciness and crispness of pear fruit in shelf life. These results showed that LTC can serve as an important tool for the regulation of Huangguan pears external and internal quality in storage and shelf life with economic benefits and LTC treatment for 6 d was the optimum condition in the present study.

Low temperature conditioning prevents loss of aroma-related esters from ‘Nanguo’ pears during ripening at room temperature

Refrigeration delays ripening and reduces decay of pear fruit, but this benefit is offset by a loss of aroma when the fruit is then ripened at room temperature. Low temperature conditioning (LTC) has been used to alleviate chilling injury (CI) of fruit, however, its effect on aroma remains unknown. Pear fruit cv. ‘Nanguo’ (Pyrus ussuriensis Maxim.) were subjected to LTC (namely, exposed to 10°C, decreased by 1°C every 3 days to 5°C, then decreased by 1°C per day to 0±0.5°C) and changes in aroma-related esters, levels of fatty acids, the activity and gene expression of alcohol acyltransferase (AAT), lipoxygenase (LOX), and alcohol dehydrogenase (ADH) were investigated. Changes in the activity and gene expression of enzymes involved in ethylene biosynthesis and the expression of genes involved in ethylene signal transduction were also studied. Significantly higher ester contents and levels of linoleic and linolenic acids were found in LTC-treated fruit. Levels of PuAAT1, PuLOX1, and PuADH3 transcripts were promoted by LTC treatment and the activity of AAT, LOX and ADH was higher in LTC-treated fruit during the shelf-life at room temperature. The increased levels of the expression and activity of 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) and ACC oxidase (ACO) contributed to the elevated ethylene levels in LTC-treated fruit. The expression of genes involved in ethylene signal transduction (PuETR1 and PuCTR1) was also promoted by LTC treatment. Treatment with LTC effectively prevented the loss of aroma-related esters from refrigerated ‘Nanguo’ pears and possible mechanisms were discussed.

Low‐temperature conditioning combined with methyl jasmonate treatment reduces chilling injury of peach fruit

AbstractBACKGROUND: Peaches are sensitive to low temperature and develop chilling injury (CI) symptoms during refrigerated storage. This CI reduces consumer acceptance of peaches and limits the potential postharvest market life of the fruit. To develop a suitable technique to reduce CI, the effect of a combination of low‐temperature conditioning (LTC) and methyl jasmonate (MJ) treatment on CI of peach fruit was investigated in this study.RESULTS: Freshly harvested firm‐mature peaches were treated with a combination of LTC at 10 or 20 °C and 1 µmol L−1 MJ and then stored at 0 °C for 5 weeks. The fruits developed CI during storage, manifested as internal browning and flesh mealiness. The combined treatment significantly reduced these CI symptoms and maintained higher fruit quality. The activities of polyphenol oxidase and peroxidase were significantly inhibited while those of superoxide dismutase, catalase and ascorbate peroxidase were induced by the combined treatment. In addition, the activities of phenylalanine ammonia‐lyase and polygalacturonase and the level of total phenolics were enhanced by the combined treatment.CONCLUSION: The combination of LTC and MJ treatment could be a useful technique to reduce CI and maintain quality in peach fruit during cold storage. Copyright © 2009 Society of Chemical Industry

Low temperature conditioning reduces postharvest chilling injury in loquat fruit

Chilling injury occurs in loquat ( Eriobotrya japonica Lindl. cv. Luoyangqing) fruit when they are stored at temperatures lower than 5 °C. In attempts to reduce this chilling injury, the effect of low temperature conditioning (LTC) was examined. Loquat fruit were conditioned at 5 °C for 6 days before 0 °C storage for up to 54 days. Control fruit stored at 0 °C exhibited severe symptoms of lignification and tissue browning, and a decrease in percentage juice. LTC treatment significantly reduced these chilling injury symptoms, and doubled storage life. In terms of acceptability (tissue browning, internal browning (IB) index <0.4; fruit decay, <10%; flesh firmness, <6.0 N; percentage juice, >60%), fruit could only be stored for 40 days at 0 °C with a 3 days shelf life at 20 °C, while LTC fruit could be stored for 60 days at 0 °C with a similar shelf life. Similarly, LTC fruit could be stored for 40 days with a 5 days shelf life at 20 °C, while fruit could be only stored for 20 days at 0 °C with a 5 days shelf life. Our results confirm that LTC can effectively alleviate postharvest chilling injury of loquat fruit and may provide longer storage life with acceptable external and internal quality.