Chilling Tolerance In Peach Fruit Research Articles

Near-Freezing Temperature Storage Improves Peach Fruit Chilling Tolerance by Regulating the Antioxidant and Proline Metabolism

Chilling injury (CI) in peach fruit (Prunus persica cv. Yuhualu) is generally caused by long-time low temperature (5 °C or 0 °C) storage. However, peach fruit stored at near-freezing temperature (NFT in this research is −1 °C), defined as within 0.5 °C above the biological freezing point of biological tissue, does not exhibit CI symptoms. The effect of NFT on the CI, proline metabolism, and antioxidant capability of peach fruit during storage was studied and compared with 5 °C and 0 °C storage as controls. The results exhibit that NFT completely inhibited the occurrence of CI in peach fruit. NFT significantly (p < 0.05) enhanced the activities of superoxide dismutase, catalase, ascorbate peroxidase, and 1,1-diphenyl-2-picrylhydrazyl scavenging capacity. Moreover, the increase of malondialdehyde, ion leakage, and H2O2 accumulation were inhibited remarkably by NFT, and decreases in the contents of phenolics and ascorbic acid were slowed significantly in peach fruit stored at NFT (p < 0.05). Additionally, NFT storage enhanced proline accumulation by modulating the activity of proline metabolizing enzymes. In conclusion, the above results suggest that NFT storage can improve the chilling tolerance of peach fruit by regulating the antioxidant defense and proline metabolism, which might represent a potential novel method to store fruits and vegetables for longer storage times.

Genome-wide identification of the CDPK gene family reveals the CDPK-RBOH pathway potential involved in improving chilling tolerance in peach fruit

Calcium-dependent protein kinase (CDPK), as an essential calcium receptor, plays a major role in the perception and decoding of intracellular calcium signaling in plant development and stress responses. Here, the CDPK gene family was analyzed at the genome-wide level in peach. This study identified 17 PpCDPK gene members from the peach genome, and systematically investigated phylogenetic relationships, conserved motifs, exon-intron structures, chromosome distribution, and cis-acting elements of each PpCDPK gene using bioinformatics. Furthermore, the expression levels of most PpCDPK genes were significantly changed under the CaCl2, EBR, GB, cold shock, hot water treatments, and various temperatures in the cold storage of peach fruits. RNA-seq data showed that PpCDPK2, PpCDPK7, PpCDPK10, and PpCDPK13 were related to postharvest chilling stress in peach. The interaction network of PpCDPK7 protein showed that the interaction between PpCDPK7 and PpRBOH may be the intersectional point of Ca2+ and ROS signal transmission during cold storage of peach fruits. These systematic analyses are helpful to further characterize the regulation of PpCDPKs and CDPK-RBOH mediated signal cascades in postharvest chilling injury in peach fruit.

24-Epibrassinolide improves chilling tolerance by regulating PpCBF5-mediated membrane lipid metabolism in peach fruit

24-Epibrassinolide plays an important role in regulating abiotic stress, which may enhance cold resistance of fruits and vegetables. C-repeat binding factor (CBF) has a rapid response to cold stress and is a crucial transcription factor for cold signal pathway. This study investigated the potential effect of EBR treatment on membrane lipid metabolism and the possible regulation mechanism of PpCBF5 to membrane lipid metabolism in peach fruit. The results showed that EBR treatment effectively suppressed the increase in activities and gene expression of phospholipase D, lipoxygenase and lipase, inhibited the hydrolysis of phosphatidylcholine and phosphatidylinositol to pohosphatidic acid, reduced the malondialdehyde content, and enhanced unsaturated fatty acids contents, thus alleviated the membrane lipid peroxidation and maintained the stability of cell membrane. In addition, the results of molecular assays in vivo, including dual luciferase reporter assay, in vivo bioluminescence imaging, yeast one hybrid and transient overexpression assay, showed that PpCBF5 negatively regulated the transcription of PpPLD and PpLipase. In conclusion, EBR treatment enhanced chilling tolerance of peach fruit through regulating membrane lipid metabolism and PpCBF5 might act as a crucial regulatory factor on membrane lipid metabolism.

CaM enhances chilling tolerance of peach fruit by regulating energy and GABA metabolism

The effects of calcium chloride (CaCl2), calmodulin antagonist trifluoperazine (TFP) and different storage temperatures on chilling injury (CI) of peach fruit during postharvest storage were studied. The results showed that 0 ℃ storage and CaCl2 treatment reduced the CI index, reduced the ion leakage and maintained the integrity of cell membrane. Storage at 0 ℃ and CaCl2 treatment increased calmodulin (CaM) expression and protein content, energy charge (EC), adenosine triphosphate (ATP) content and adenosine diphosphate (ADP) content. At the same time, it also promoted the expression and activity of Ca2+-ATPase and other enzymes related to energy metabolism. In addition, storage at 0 ℃ and CaCl2 treatment promoted the expression and activity of glutamic acid decarboxylase (GAD), and increased the content of γ-aminobutyric acid (GABA) and the expression of GABA transaminase (GABA-T). On the contrary, TFP treatment significantly increased CI index and ion leakage, significantly inhibited PpCaM expression and protein content, and decreased EC and GABA content. Moreover, the molecular properties of PpCaM were studied. The results showed that PpCaM was a highly conserved hydrophilic protein, located on the nucleus and plasma membrane. PpCaM could induce the expression of PpCa2+-ATPase, increase the activity of Ca2+-ATPase, and participate in the regulation of energy metabolism. In addition, PpCaM could activate the activity of PpGAD, promote the synthesis of GABA, and participate in the regulation of GABA metabolism. These results suggested that 0 ℃ storage and CaCl2 treatment promoted the expression of PpCaM and increased the protein content of PpCaM, suggesting PpCaM enhanced the cold resistance and reduced the occurrence of CI by participating in the regulation of energy metabolism and GABA metabolism.

Postharvest nitric oxide treatment induced the alternative oxidase pathway to enhance antioxidant capacity and chilling tolerance in peach fruit

Nitric oxide (NO) is an important regulator of plant response to cold stress. In this study, NO treatment delayed the development of chilling injury (CI), inhibited the increase in H2O2 content, O2− production rate and decrease in firmness of postharvest peach fruit. Meanwhile, through RNA-seq analysis, NO treatment up-regulated gene expression of PpG-6-PDH, Pp6-PGDH and PpAOX while it down-regulated the expression of PpGPI and PpHK, suggesting that the pentose phosphate respiratory pathway and cyanide-resistant respiratory pathway were promoted and the glycolysis pathway was inhibited. Furthermore, the PpAOX expression was consistent with the trend of PpPOD1/2 expression and H2O2 content, indicating that AOX may play a role in reducing oxidative damage of peach fruit by scavenging H2O2. Thus, it was concluded that NO treatment could induce the cyanide-resistant respiration pathway to enhance antioxidant ability and chilling tolerance in post-harvest peach fruit.

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.

PpINH1, an invertase inhibitor, interacts with vacuolar invertase PpVIN2 in regulating the chilling tolerance of peach fruit

Sucrose metabolism, particularly the decomposition of sucrose by invertase, plays a central role in plant responses to cold stress. Invertase inhibitors (INHs) evolved in higher plants as essential regulators of sucrose metabolism. By limiting invertase activity, INHs keep cellular sugar levels elevated, which provides enhanced protection to plants under stress. Our results showed that the expression of PpVIN2, the only vacuolar invertase (VIN) gene in peach fruit sensitive to chilling temperatures, increases significantly during cold storage, while VIN enzyme activity increases more modestly. We also found that peach fruit transiently overexpressing PpINH1 had decreased VIN activity. Interactions of PpINH1 and PpVIN2 with recombinant proteins were shown by yeast two-hybrid assays and bimolecular fluorescence complementation assays, as well as in vitro. During cold storage, trehalose-treated peach fruit had significantly increased PpINH1 expression, decreased VIN enzyme activity, and significantly higher sucrose content than did untreated fruit. As a result, the treated fruit had enhanced resistance to chilling injury. Collectively, our data show that the post-translational repression of VIN enzyme activity by PpINH1 helps maintain sucrose levels in peach fruit during cold storage, thereby improving resistance to 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.

The Mediation of NO-Enhanced Chilling Tolerance by GSK-3 in Postharvest Peach Fruit

The role of glycogen synthase kinase-3 (GSK-3) in nitric oxide (NO)-enhanced chilling tolerance in postharvest peach fruit was investigated. The fruits were immersed in sodium nitroprusside (SNP; exogenous NO donor) and bikinin (GSK-3 inhibitor). Results showed that the chilling injury (CI) index declined following the exposure of the peach fruit to exogenous SNP. SNP treatment also induced GSK-3 expression. Furthermore, SNP treatment reduced malondialdehyde (MDA) content and electrolyte leakage in the peach fruit. In addition, SNP treatment induced the increase in alternative oxidase (AOX) activity and the upregulation of the gene expression of 18.1-kDa class I heat shock protein (HSP), WRKY2, and C-repeat binding factor (CBF). The effects of SNP treatment were partly weakened by the addition of bikinin. These findings indicate that GSK-3 mediated the reduction of MDA content and electrolyte leakage and the activation of AOX, 18.1-kDa class I HSP, WRKY2, and CBF by NO, thereby inducing chilling tolerance in peach fruit.

The Role of IP3 in NO-Enhanced Chilling Tolerance in Peach Fruit.

The role of inositol 1,4,5-trisphosphate (IP3) in nitric oxide (NO)-reduced chilling injury (CI) in peach fruit was investigated. The fruit were immersed in sodium nitroprusside (SNP) (NO donor) and neomycin (IP3 inhibitor). Results showed that chilling tolerance was enhanced upon exogenous SNP in postharvest peach fruit. Further, GABA accumulation was stimulated by SNP. The increase in protein expression and activity for enzymes in GABA biosynthesis, including glutamate decarboxylase (GAD), polyamine oxidase (PAO), and amino aldehyde dehydrogenase (AMADH), upon SNP treatment was also observed. Also, the up-regulation of Δ1-pyrroline-5-carboxylate synthetase (P5CS) and ornithine d-aminotransferase (OAT) and the down-regulation of proline dehydrogenase (PDH) were induced by SNP treatment, thereby accelating proline production. Additionally, SNP treatment elevated protein expression and activity of alternative oxidase (AOX). The above effects induced upon SNP were partly weakened by neomycin. Therefore, IP3 mediated NO-activated GABA and proline accumulation as well as AOX, thus inducing chilling tolerance in postharvest peach fruit.

Interactions among chilling tolerance, sucrose degradation and organic acid metabolism in UV-C-irradiated peach fruit during postharvest cold storage

UV-C irradiation treatment has been demonstrated to be able to enhance chilling tolerance in peach (Prunus persica L. Batsch) during postharvest cold storage. Sugar and organic acid play central roles in plant metabolism. However, little is known about the relationships among chilling injury, soluble sugar and organic acid in peaches subjected to UV-C. In this study, peaches were irradiated with UV-C (1.5 kJ/m2) and then stored at 1 °C for 35 days. The content of sugar and organic acid, activities of enzymes, and the expression of enzyme genes that catalyze the metabolism of sugar and acid were evaluated. Results showed that UV-C significantly alleviated chilling injury and maintained the quality of peaches during storage. For sugar metabolism, UV-C suppressed sucrose degradation and glucose production mostly by inhibiting the enzyme activity and mRNA transcription of invertase (β-d-fructofuranoside fructohydrolase; EC 3.2.1.26) during the cold storage. For organic acid metabolism, UV-C irradiation downregulated the enzyme activities and gene expressions of aconitase (citrate hydrolyase; EC 4.2.1.3), and NADP-malic enzyme (S-malate: NADP-oxidoreductase; EC 1.1.1.40), but upregulated the enzyme activities and gene expressions of citrate synthase (acetyl-CoA: oxaloacetate C-acetyltransferase; EC 2.3.3.1) and NAD-malate dehydrogenase (l-malate: NAD-oxidoreductase; EC 1.1.1.37), leading to the low degradation of citric and malic acids during the whole storage periods. These results suggest that UV-C enhanced chilling tolerance in peach fruit during cold storage by suppressing the degradations of sucrose, citric, and malic acids.

Sodium nitroprusside (SNP) spray to maintain fruit quality and alleviate postharvest chilling injury of peach fruit

Peaches, cultivar ‘G.H. Hill’, from trees that were sprayed with 0, 25, 50 and 100μmolL−1 sodium nitroprusside (SNP) 14days before harvest were stored at 4°C for 4 weeks. Chilling injury (CI), ethylene production, weight loss, firmness, malondialdehyde, hydrogen peroxide and vitamin C concentrations, antioxidant capacity (AC), and superoxide dismutase, peroxidase and polyphenol oxidase activities in the fruit were measured during storage. SNP treatments reduced ethylene production and maintained firmness, AC and vitamin C of the fruit. Treatment with 25 and 50μmolL−1 SNP reduced CI but 100μmolL−1 SNP increased it. SNP at 100μmolL−1 promoted the accumulation of reactive oxygen species, decreased the activity of antioxidant enzymes and accelerated peroxidation in fruit during storage. These results indicated that preharvest SNP (25 and 50μmolL−1) treatment increased chilling tolerance of peach fruit through suppressing ethylene production, maintaining firmness, AC and vitamin C and enhancing anti-oxidative enzyme activity.

Sucrose degradation is regulated by 1-methycyclopropene treatment and is related to chilling tolerance in two peach cultivars

In order to reveal how sucrose degradation is related to chilling tolerance, two varieties of peach fruit, ‘Zajiao’ and ‘Yulu’, were treated with 1-methylcyclopropene (1-MCP) vapor at 1μL/L for 24h before storage at 5°C for 35 and 28d respectively. ‘Yulu’ peaches had higher sucrose content than ‘Zajiao’ peaches at harvest, but a higher rate of sucrose degradation in untreated ‘Yulu’ fruit may have resulted greater sensitivity to chilling stress compared with untreated ‘Zajiao’ fruit. 1-MCP treatment significantly inhibited chilling injury (CI) and preserved higher firmness values in both varieties. This treatment reduced the activities and expression of enzymes related to sucrose degradation, and increased activity and expression of sucrose synthase synthesis, resulting in a lower rate of sucrose degradation and the increase of glucose and fructose content in both varieties during cold storage. These results suggest that lower degradation rates of sucrose during cold stress, rather than the higher content of sucrose at harvest time, enhances chilling tolerance in peach fruit.

Exogenous glycine betaine treatment enhances chilling tolerance of peach fruit during cold storage

The effect of exogenous glycine betaine (GB) treatment on chilling injury (CI), energy status, endogenous GB, γ-aminobutyric acid (GABA) and proline content in cold-stored peach fruit was investigated. The results showed that GB treatment significantly prevented CI and maintained low flesh firmness and high extractable juice in peach fruit during cold storage. The accumulation of endogenous GB, GABA and proline contents in peaches was enhanced by GB treatment resulting from increasing activities of metabolism enzymes, including betaine aldehyde hydrogenase (BADH), glutamate decarboxylase (GAD), Δ1-pyrroline-5-carboxylate synthetase (P5CS) and ornithine δ-aminotransferase (OAT). Moreover, high level of energy status in GB-treated peach fruit was found. These results indicated that GB treatment enhanced chilling tolerance in peaches due to induction of energy status, endogenous GB, GABA and proline contents, which prevented membrane damage. Thus, exogenous GB treatment could be a useful method to reduce CI in peach fruit during cold storage.

Effect of 24-epibrassinolide on chilling injury of peach fruit in relation to phenolic and proline metabolisms

Peach fruit is cold-sensitive and vulnerable to chilling injury (CI) during cold storage, which limits its edible and market value. Brassinosteroids (BRs) have been used to alleviate CI of fruit; however, the effect of BRs on CI of peach fruit remains unknown. In this study, peach fruit were immersed in a 15μM 24-epibrassinolide (EBR) solution for 10min at 25°C and then stored at 1°C for 4 weeks and subsequently transferred to 25°C for 3d to investigate the effects and possible mechanisms of EBR on CI in peach fruit. EBR treatment effectively inhibited the loss of firmness and delayed the increase of CI index and levels of malondialdehyde, superoxide anion production, and hydrogen peroxide in peach fruit. EBR treatment significantly increased shikimate dehydrogenase, phenylalanine ammonia lyase, cinnamate-4-hydroxylase and 4-coumarate: coenzyme A ligase activity, but reduced polyphenol oxidase and peroxidase activity, which resulted in a higher total phenolic content that might contribute to inhibition of the CI. The treatment also significantly enhanced the accumulation of proline associated with increase in the activity of Δ1-pyrroline-5-carboxylate synthetase and decrease in proline dehydrogenase activity. These results indicate that EBR treatment may be an effective strategy to induce chilling tolerance of peach fruit, and the EBR-mediated amelioration of CI may be attributed to activation of phenolic and proline biosynthesis as well as inhibition of oxidative stress.

The metabolism of soluble carbohydrates related to chilling injury in peach fruit exposed to cold stress

In order to elucidate the metabolism of soluble carbohydrates related to chilling injury (CI) in peach fruit (Prunus persica L. Batsch cv. Yulu) exposed to cold storage, we systematically investigated the changes in soluble carbohydrate content, transcript levels for genes encoding related enzymes, and the ascorbic acid (AsA) regeneration cycle in fruit stored at 0°C and 5°C for 28 days. At 0°C, sucrose levels gradually increased up to day 21 before declining, but no significant changes of reducing-sugar levels (glucose and fructose) were observed during this time. However, the levels of sucrose decreased sharply and reducing-sugar levels increased during storage at 5°C. Thus, fruit stored at 0°C showed significantly higher levels of sucrose and lower levels of glucose and fructose than fruit stored at 5°C. This difference was primarily due to lower transcription levels for neutral invertase 2 (NI/2), acid invertase (AI) and sucrose synthase (SS) and lower activities of NI and AI, and higher levels for sucrose phosphate synthase 1 (SPS/1). Both groups of fruit displayed an early, dramatic increase in the transcription levels of sorbitol and sorbitol dehydrogenase (SDH). Additionally, stable membrane permeability, a lack of CI symptoms and a regular AsA cycle were observed throughout the test period in fruit stored at 0°C. On the other hand, membrane permeability increased sharply in fruit stored at 5°C, which caused severe internal browning and stimulated AsA cycle activity later in storage. These results suggest that the higher levels of sucrose, resulting from the balance between its degradation and biosynthesis, contribute to membrane stability and enhanced chilling tolerance in peach fruit. Additionally, higher levels of glucose may have provided more reducing power and served as a substrate for AsA biosynthesis, which resulted in enhanced AsA cycle activity in chilling-sensitive fruit.

Effect of methyl jasmonate on energy metabolism in peach fruit during chilling stress

Energy status is associated with ripening, senescence and physiological disorder of various types of fruit after harvest, including peaches. Methyl jasmonate (MeJA) was effective in enhancing chilling tolerance in cold-stored peach fruit. The effect of MeJA on energy metabolism in peach fruit was investigated. MeJA treatment increased the contents of adenosine triphosphate and adenosine diphosphate, but decreased the content of adenosine monophosphate, which resulted in a higher level of energy charge in peach fruit. Enzyme activities including H+-adenosine triphosphatase, Ca2+-adenosine triphosphatase, succinic dehydrogenase and cytochrome c oxidase were also higher in MeJA-treated fruit than those in control fruit. Meanwhile, MeJA treatment markedly inhibited the increase of ion leakage and the accumulation of malondialdehyde, super-oxidant radical and hydrogen peroxide. These results indicated that MeJA could enhance chilling tolerance of peach fruit by inducing enzyme activities related to energy metabolism and maintaining high levels of ATP and energy charge.

γ-Aminobutyric acid treatment reduces chilling injury and activates the defence response of peach fruit

Peach fruit were immersed in 5mM γ-aminobutyric acid (GABA) solution for 10min at 20°C and then stored at 1°C for 5weeks to investigate the effect of GABA treatment on chilling injury (CI), antioxidant enzymes and energy status in peach fruit. The results showed that GABA treatment significantly inhibited CI incidence of peaches and enhanced activities of antioxidant enzymes, such as superoxide dismutase, catalase, ascorbate peroxidase, glutathione peroxidase, glutathione S-transferase, monodehydroascorbate reductase and dehydroascorbate reductase. The treatment also increased contents of adenosine triphosphate and adenosine diphosphate, but lowered adenosine monophosphate content, which resulted in a higher level of energy charge in treated fruit. These results indicated that GABA increased chilling tolerance of peach fruit through enhancing its enzymatic antioxidant system and maintaining energy status in peach fruit.

Peach fruit acquired tolerance to low temperature stress by accumulation of linolenic acid and N-acylphosphatidylethanolamine in plasma membrane

Peach fruit (Prunus persica L. cv. Beijing 33) did not show symptoms of chilling injury in 0 C-Air or 0 C- CA, but did in 5 C-Air after 21 d. The mechanisms by which 0 C storage could activate chilling tolerance of peach fruit were investigated by analysing characteristics of plasma membrane. We found that peach fruit stored in 0 C-Air and 0 C-CA had much higher linolenic acid content and unsaturation degree of plasma membrane than did that in 5 C-Air. In addition, the fruits stored in 0 C-CA showed a higher membrane fluidity and membrane integrity than did that in 0 C-Air, which was related to the accumu- lation of N-acylphosphatidylethanolamine (NAPE) of peach fruits stored in 0 C-CA. Based on these results, it appears that a higher unsaturation degree of membrane lipid and NAPE accumulation are ben- eficial for maintaining membrane fluidity, leading to an enhanced tolerance of peach fruit to chilling stress.

Crucial contribution of membrane lipids’ unsaturation to acquisition of chilling-tolerance in peach fruit stored at 0°С

Abstract Peach fruits ( Prunus persica L.) were less prone to chilling injury (CI) when stored at 0 °С than at 5 °С for 30 days. In order to make known the mechanism involved, the relationship between CI and membrane lipid unsaturation was investigated in this study. The results demonstrated that peach fruit stored at 0 °С manifested higher membrane lipid fluidity and higher membrane lipid unsaturation than at 5 °С. In addition, a higher omega-3 fatty acid desaturase gene ( FAD ) mRNA level and a higher level of linolenic acid (C18:3) were found when peach fruits were stored at 0 °С. The findings indicated that the higher membrane lipid unsaturation in peach fruit stored at 0 °С was beneficial in maintaining membrane lipid fluidity and enhancing tolerance of peach fruit to low temperature stress, and the C18:3 level could be regulated by omega-3 FAD .