Chilling Resistance Research Articles

Influence of Foliar Application of Nanoparticles on Low Temperature Resistance of Rice Seedlings.

Chilling stress, a common abiotic factor, adversely affects the growth and biomass of rice seedlings during the early stages, ultimately reducing the yield. Effective strategies to mitigate these negative impacts are essential for improving rice productivity. The application of nanotechnology in agriculture, particularly nanoparticles (NPs), has shown a promising effect in alleviating chilling stress in plants. This study evaluates the effects of various nanoparticles, ZnO (0, 50, 100, and 200 mg/L), Fe2O3 (0, 50, 75, and 100 mg/L), TiO2 (0, 50, 75, and 100 mg/L), and CeO2 (0, 50, 75, and 100 mg/L) on the chilling resistance with one control (a water spray) under a normal temperature. Four rice cultivars: LLY-7108 and XZX-6 (Low-temperature-tolerant), and LLY-32 and ZJZ-17 (Low-temperature-susceptible) were tested in this experiment. Rice seedlings were subjected to low temperature conditions (12 h light 14 °C/12 h dark, at 10 °C) for five days, followed by seven days of recovery. The results of this study demonstrate that NPs significantly enhanced seedling height fresh/dry weight and root length compared to untreated controls under chilling stress. NP treatment also reduced the reactive oxygen species (ROS), malondialdehyde (MDA), and proline content, while enhancing superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities, thereby mitigating oxidative damage. The four rice varieties exhibited clear signs of rapid growth recovery and positive physiological changes due to NPs' application. Among the tested cultivars, LLY-7108 showed the most substantial recovery and physiological responses, while ZJZ-17 exhibited the least. The findings of this study indicate that the foliar application of ZnO (100 mg/L), Fe2O3 (50 mg/L), TiO2 (50 mg/L), and CeO2 (75 mg/L) NPs effectively mitigates chilling stress in rice seedlings, likely by enhancing the antioxidant enzymatic activity while reducing the oxidative damage. This study highlights the potential of NPs as effective agents in reducing the adverse effects of chilling stress on rice.

Current status for utilization of cold resistance genes and strategies in wheat breeding program.

Low temperature chilling is one of the major abiotic stresses affecting growth and yield of Triticum aestivum L. With global climate change, the risk of cold damage in wheat production has increased. In recent years, with the extensive research on wheat chilling resistance, especially the development of genetic engineering technology, the research on wheat chilling resistance has made great progress. This paper describes the mechanism of wheat cold damage, including cell membrane injury, cytoplasmic concentration increased as well as the imbalance of the ROS system. Mechanisms of cold resistance in wheat are summarised, including hormone signalling, transcription factor regulation, and the role of protective enzymes of the ROS system in cold resistanc. Functions of cloned wheat cold resistance genes are summarised, which will provide a reference for researchers to further understand and make use of cold resistance related genes in wheat. The current cold resistant breeding of wheat relies on the agronomic traits and observable indicators, molecular methods are lacked. A strategy for wheat cold-resistant breeding based on QTLs and gene technologies is proposed, with a view to breeding more cold-resistant varieties of wheat with the deepening of the research.

An AP2/ERF transcription factor confers chilling tolerance in rice.

Cold stress, a prominent adverse environmental factor, severely hinders rice growth and productivity. Unraveling the complex mechanisms governing chilling tolerance in rice is crucial for molecular breeding of cold-tolerant varieties. Here, we identify an APETALA2/Ethylene Responsive Factor (AP2/ERF) transcription factor, OsERF52, as a positive modulator in response to low temperatures. OsERF52 directly regulates the expression of C-Repeat Binding Factor (CBF) genes in rice. In addition, Osmotic Stress/ABA-Activated Protein Kinase 9-mediated phosphorylation of OsERF52 at S261 enhances its stability and interaction with Ideal Plant Architecture 1 and OsbHLH002/OsICE1. This collaborative activation leads to the expression of OsCBFs, thereby initiating the chilling response in rice. Notably, plants with base-edited OsERF52S261D-3HA exhibit enhanced chilling resistance without yield penalty. Our findings unveil the mechanism orchestrated by a regulatory framework involving a protein kinase and transcription factors from diverse families, offering potential genetic resources for developing chilling-tolerant rice varieties.

Photosynthesis and Latex Burst Characteristics in Different Varieties of Rubber Trees (Hevea brasiliensis) under Chilling Stress, Combing Bark Tensile Property and Chemical Component Analysis

Rubber trees (Hevea brasiliensis) serve as the primary source of natural rubber. Their native habitat is characterized by warm and humid conditions, so they are particularly sensitive to low temperatures. Under such stress, latex burst can cause severe damage to rubber trees, which is due to the uniqueness of their economically productive parts. In order to establish a correlation between young and mature rubber trees and provide a novel prospective for investigating the mechanisms of latex burst and chilling resistance in rubber trees, the chlorophyll contents, photosynthesis, and chlorophyll fluorescence parameters in four varieties of one-year-old rubber tree seedlings were analyzed under artificially simulated chilling stress. The latex burst characteristics were subsequently recorded. A comprehensive statistical analysis of the chilling-resistance rank was conducted using the membership function method and the combination weighting method. Meanwhile, chemical compositions and tensile properties of barks from two-year-old twigs of mature rubber trees were ascertained. A correlation analysis between chilling resistance, chemical compositions, and tensile properties was performed to identify any interrelationships among them. The results showed that the number and the total area of latex-burst positions in variety Reken628 seedlings were greater than those in other varieties, and the lowest number and total area of latex-burst positions were observed in variety RRIM600 and variety PR107, respectively. With the exception of variety GT1, nectar secretion was noted in all other varieties of rubber tree seedlings under chilling stress. The chilling resistance of the four varieties decreased in the following order: variety GT1 > variety RRIM600 > variety PR107 > variety Reken628. The chilling resistance was strongly (p < 0.001) negatively correlated with cellulose content and acid-insoluble lignin content, respectively. The total area of latex burst was significantly (p < 0.001) and positively correlated with holocellulose content and maximum load, respectively. Furthermore, this study also provides new insights into the mechanism of nectar secretion induced by low temperatures and its association with the chilling resistance of rubber trees.

SMRT sequencing of a full-length transcriptome reveals cold induced alternative splicing in Vitis amurensis root

Alternative splicing enhances diversity at the transcriptional and protein levels that widely involved in plant response to biotic and abiotic stresses. V. amurensis is an extremely cold-tolerant wild grape variety, however, studies on alternative splicing (AS) in amur grape at low temperatures are currently poorly understood. In this study, we analyzed full-length transcriptome and RNA seq data at 0, 2, and 24 h after cold stress in V. amurensis roots. Following quality control and correction, 221,170 high-quality full-length non-concatemer (FLNC) reads were identified. A total of 16,181 loci and 30,733 isoforms were identified. These included 22,868 novel isoforms from annotated genes and 2815 isoforms from 2389 novel genes. Among the distinguished novel isoforms, 673 Long non-coding RNAs (LncRNAs) and 18,164 novel isoforms open reading frame (ORF) region were found. A total of 2958 genes produced 8797 AS events, of which 189 genes were involved in the low-temperature response. Twelve transcription factors show AS during cold treatment and VaMYB108 was selected for initial exploration. Two transcripts, Chr05.63.1 (VaMYB108short) and Chr05.63.2 (VaMYB108normal) of VaMYB108, display up-regulated expression after cold treatment in amur grape roots and are both localized in the nucleus. Only VaMYB108normal exhibits transcriptional activation activity. Overexpression of either VaMYB108short or VaMYB108normal in grape roots leads to increased expression of the other transcript and both increased chilling resistance of amur grape roots. The results improve and supplement the genome annotations and provide insights for further investigation into AS mechanisms during cold stress in V. amurensis.

Exogenous Gibberellic Acid Ameliorates Chilling Injury in Peach (Prunus persica L.) by Improving the Antioxidant System

Currently, several studies have demonstrated that cold stress can cause the accumulation of reactive oxygen species (ROS) in fruit. However, little is known about the roles of gibberellic acid (GA3) on the antioxidant system in the mitochondria of fruit. To explore the molecular basis of GA3 interference with the chilling tolerance of fruit, ‘Jinqiuhongmi’ peach fruit was treated with 0.1 mmol L−1 GA3 after harvest. Exogenous GA3 treatment relieved the chilling injury of postharvest peach fruit with a lower cold injury index and higher antioxidant level. In addition, GA3 delayed the senescence of peaches by reducing the firmness, respiratory action, and ethylene production. The antioxidant enzyme activities were elevated, including superoxide dismutase (SOD) and catalase (CAT). Moreover, GA3-treated peaches exhibited lower hydrogen peroxide (H2O2) and malondialdehyde (MDA) in comparison with the control. These results showed that the application of 0.1 mmol L−1 of GA3 enhanced the chilling resistance of peach fruit by regulating the antioxidant system.

PbrWRKY62-PbrADC1 module involves in superficial scald development of Pyrus bretschneideri Rehd.fruit via regulating putrescine biosynthesis

Putrescine plays a role in superficial scald development during the cold storage of pear fruit. However, the molecular mechanism behind this phenomenon has not been un-fully clarified until recently. In this study, a conjoint analysis of metabolites and gene expression profiles in the putrescine-metabolic pathway of P. bretschneideri Rehd. fruit followed by experimental validation revealed that PbrADC1, forming a homodimer in the chloroplast, was involved in putrescine biosynthesis and thus fruit chilling resistance. Additionally, the substrate-binding residue Cys546 in PbrADC1, whose activity was modified by H2O2, played a crucial role in arginine decarboxylation into agmatine. Through a combined analysis of the distribution of cis-acting elements in the PbrADC1 promoter as well as the expression profiles of related transcription factors (TFs), several TFs were identified as upstream regulators of PbrADC1 gene. Further investigation revealed that the nuclear PbrWRKY62 could directly bind to the W-box elements in the PbrADC1 promoter, activate its expression, enhance putrescine accumulation, and thus increase fruit chilling tolerance. In conclusion, our results suggest that the PbrWRKY62-PbrADC1 module is involved in the development of superficial scald in P. bretschneideri Rehd. fruit via regulating putrescine biosynthesis. Consequently, these findings could serve as valuable genetic resources for breeding scald-resistant pear fruit.Graphical

ABC transporter SlABCG23 regulates chilling resistance of tomato fruit by affecting JA signaling pathway

To explore the effect and mechanism of an ATP-binding cassette transporter, SlABCG23, on the chilling resistance of tomato fruit during storage, we generated mutant using CRISPR/Cas9 technology for further investigation. This research showed under cold stress, the slabcg23 mutant fruit exhibited severe chilling injury (CI), lower jasmonic acid (JA) contents, and higher expression levels of JA signaling inhibitor, SlJAZ6, than wild-type (WT). The mutation of SlABCG23 caused a decrease in the thickness of the fruit pericarp. The expression levels of SlCBF1 and SlICE1 in slabcg23 mutant fruit were lower than those in WT fruit under cold stress. Moreover, the slabcg23 mutant fruit exhibited reduced activities of antioxidant enzymes, including superoxide dismutase, catalase and peroxidase, and increased reactive oxygen species and malondialdehyde contents. These findings indicated that SlABCG23 affects fruit resistance to CI by influencing the JA signaling pathway, fruit pericarp development, cold response signal and antioxidant capacity.

Transcription factor SlWRKY50 enhances cold tolerance in tomato by activating the jasmonic acid signaling.

Tomato (Solanum lycopersicum) is a cold-sensitive crop but frequently experiences low-temperature stimuli. However, tomato responses to cold stress are still poorly understood. Our previous studies have shown that using wild tomato (Solanum habrochaites) as rootstock can significantly enhance the cold resistance of grafted seedlings, in which a high concentration of jasmonic acids (JAs) in scions exerts an important role, but the mechanism of JA accumulation remains unclear. Herein, we discovered that tomato SlWRKY50, a Group II WRKY transcription factor that is cold inducible, responds to cold stimuli and plays a key role in JA biosynthesis. SlWRKY50 directly bound to the promoter of tomato allene oxide synthase gene (SlAOS), and overexpressing SlWRKY50 improved tomato chilling resistance, which led to higher levels of Fv/Fm, antioxidative enzymes, SlAOS expression, and JA accumulation. SlWRKY50-silenced plants, however, exhibited an opposite trend. Moreover, diethyldithiocarbamate acid (a JA biosynthesis inhibitor) foliar treatment drastically reduced the cold tolerance of SlWRKY50-overexpression plants to wild-type levels. Importantly, SlMYC2, the key regulator of the JA signaling pathway, can control SlWRKY50 expression. Overall, our research indicates that SlWRKY50 promotes cold tolerance by controlling JA biosynthesis and that JA signaling mediates SlWRKY50 expression via transcriptional activation by SlMYC2. Thus, this contributes to the genetic knowledge necessary for developing cold-resistant tomato varieties.

Postharvest 24-epibrassinolide treatment improves chilling resistance of peach fruit via PpHDT1 modulating brassinosteroid metabolism

Brassinosteroids (BRs) exhibit a positive effect on facilitating chilling resistance in fruits and vegetables. However, the change and regulatory mechanism of BR metabolism in fruits and vegetables are poorly understood. This study aimed to explore the underlying relationship among chilling injury (CI), BR metabolism and regulatory factor PpHDT1. The results showed that exogenous 24-epibrassinolide (EBR) retarded peaches CI, reduced endogenous brassinolide (BL) accumulation, repressed the transcriptions of BR synthesis-related genes, promoted expression of BR signal-related genes. The results of molecular assays in vivo demonstrated that PpHDT1 down-regulated BR synthesis gene PpDWF4 and up-regulated BR signal transduction gene PpBZR1. Moreover, EBR treatment enhanced PpHDT1 expression, revealing that EBR treatment might alleviate peaches CI through PpHDT1 modulating BL metabolism and signal pathway. Our study provides a new insight into the underlying mechanism of EBR on regulating chilling resistance in postharvest peaches.

SlMsrB5 contributes to the chilling tolerance induced by methyl jasmonate in postharvest tomato fruit

Chilling injury (CI) is a common phenomenon during low temperature storage for most fruits, reducing the effectiveness of refrigeration methods. Methyl jasmonate (MeJA) has been extensively employed to extend the shelf life of fruits during cold storage. However, the mechanism of MeJA inducing fruit resistance to CI requires further investigation. The study found that treating tomatoes with 0.05 mM MeJA inhibited CI by regulating the reactive oxygen species (ROS) metabolism, polyamines, and jasmonic acid (JA) signaling pathway, as well as cold response pathway. Interestingly, the expression of SlMsrB5 in tomato was up-regulated under MeJA treatment, showing an increase of 36.44% to 161.75% compared to the control fruit. Notably, silencing the expression of SlMsrB5 led to a continuously increased in CI incidence by 52.17% and CI index by 36.58% compared to the control fruit at the end of storage. Additionally, the silencing of SlMsrB5 weakened the inhibitory impact of MeJA on CI and reduced its induction effects on the aforementioned indicators. In addition, correlation analysis showed that the transcription of SlMsrB5 has a negative correlation with ROS related indicators under MeJA treatment, while was highly correlated with the aforementioned induction effects controlled by MeJA. Therefore, this study demonstrates a new basis for revealing the underlying mechanisms in the MeJA-regulated chilling resistance in postharvest fruits.

Functional characterization of dehydrins CpRAB and CpERD and their roles in regulating cold resistance of zucchini fruit under high relative humidity storage

The contribution of CpERD and CpRAB on cold resistance of zucchini fruit under high relative humidity (HRH) storage was studied. The results showed that higher accumulations of CpRAB and CpERD were associated with decreased chilling injury in zucchini. HRH storage maintained a higher level of CpDREB1–5 expression and further activated the transcription of CpRAB and CpERD. CpRAB and CpERD exhibited protective roles in lactate dehydrogenase activity in vitro and cell activity of transformed E.coli in vivo under stresses. In addition, CpRAB and CpERD physically interacted with the CpSOD1 and CpCAT2 of zucchini. The transient expression of CpRAB and CpERD maintained higher antioxidant activities in tobacco leaves under cold stress. Taken together, the results suggested that accumulations of CpRAB and CpERD under HRH storage enhanced the chilling resistance of zucchini fruit, which may be due to their potential protective function of enzyme activities under cold and oxidative stress.

Unraveling molecular mechanisms underlying low-temperature adaptation in Laguncularia racemosa

Laguncularia racemosa (L.) C.F. Gaertn is a controversial species in China, in terms of being a pioneer species for mangrove restoration and a putative invasive species occupying natural habitats. The tolerance to chilling stress allows L. racemosa to adapt to extreme climate change. However, little is known about the molecular-level chilling resistance mechanisms in L. racemosa, which restricts our understanding of its biological features and invasion potential. In this study, L. racemosa seedlings were treated with freezing temperature (0 °C) at four durations (0 h, 3 h, 12 h and 24 h of recovery after treatment), and both physiological and transcriptional regulations underlying chilling stress resistance were investigated. Chilling stress caused damage to the cell membrane system and reduced photosynthesis efficiency of L. racemosa seedlings. To combat the adverse impacts, plasma membrane biosynthesis and antioxidant processes were substantially enhanced. After 24 h of recovery, the seedlings nearly recovered to normal growth condition, except for the processes related to photosynthesis, indicating their vigorous adaptation to short-term chilling stress. Importantly, the individuals from higher latitude displayed better adaptation to chilling injury than those from lower latitude, highlighting the role of long-term heredity × environment interactions in promoting the chilling resistance capacity of L. racemosa. These features allow L. racemosa to survive in extremely cold weather, but may also increase its risk of invasion into intertidal ecosystems. Together, our findings present a comprehensive view of the chilling-adaptative mechanisms of L. racemosa, which provide clues for better evaluating the invasive potential of L. racemosa.

Transcriptome analyses revealed chilling response genes in mango (Mangifera indica L. cv. Keitt) leaf

ABSTRACT Mangifera indica L. cv. Keitt is a cold-stress fruit plant native to China's drought river valley. Chilling stress affects productivity. Understanding the mechanisms of chilling stress is important to increasing chilling resistance in mango. Leaves of Keitti were subjected to 4 °C for 0, 3, 6, and 9 h for RNA-Seq-based transcriptome analysis, respectively. The chlorophyll content, carotenoid content, catalase, and peroxidase activities significantly increased during 9 h. The leaves responded to the stress by enhancing photosynthetic pigment content and antioxidant enzyme activity. After 3 h of chilling, 410 genes were differentially expressed. WRKY70 and PLD1 were significantly up-regulated after 9 h. Compared to 9 and 0 h, there were 1123 DEG. The DEGs are enriched in hormonal signal transduction, secondary metabolites, and the abiotic stress response. Similarly, the transcriptional factor families including NCED2, MYB73, and HLH162 up-regulated. The study will promote research on the development of chill-resistant mangoes.

Cold priming improves chilling resistance in wheat seedlings: Changing of photosystem II imprints during recovery from priming

Chilling stress oriented from frequent extreme events has seriously depressed growth and productivity of wheat. Cold priming can effectively improve cold tolerance of crops. However, it is still unclear about the changes of stress memory imprints during recovery from priming and the potential function of the imprints on improved cold tolerance. Here we subjected wheat plants to cold priming (10 °C/6 °C, 1 d) at the trifoliate stage, and then to chilling stresses (2 °C/0 °C, 1 d) at 3, 6, 9, 12, 15 and 18 days of recovery from priming, respectively. Compared with non-primed plants (NL), primed plants (PL) showed the most obvious resistance phenotype at 9 days after priming. Its terminal spreading leaves exhibit temporally specific physiological memory and persistent a high photochemical quenching capacity of photosystem II after priming. In addition, it appeared faster photosynthetic performance in the post-stress rewarming phase during 3–12 days after priming. Further analysis of different leaf positions revealed that priming increased light energy absorption by the augmented antennal pigments content and synthesis of light-harvesting proteins, and a higher percentage of primary and secondary quinone electron acceptors (QAQB) active reaction centers (RCs) which enhanced energy capture and transfer performance in primed control plants (PC). Meanwhile, the increased antenna pigments in PC indirectly affected PL. Compared with NL, priming increased electron flux into the inter-system by alleviating the degradation of antenna pigments and increased Photosystem II Subunit S (PsbS) gene expression to promote the occurrence of non-photochemical quenching (NPQ), lowered the excitation pressure per RC, and increased the percentage of QA-RCs, it finally improved the light energy absorption and utilization capacity in PL. In summary, priming-induced memory is mainly present in primed leaves (3rd and 4th leaves during R6-R15) and diminishes with spatial and temporal changes, it exists even no obvious difference in phenotype. This study contributes to a deeper understanding of the long-term effects of fluctuating temperatures on the plant.

Exogenous Ca2+ priming can improve peanut photosynthetic carbon fixation and pod yield under early sowing scenarios in the field.

Harnessing cold-resilient and calcium-enriched peanut production technology are crucial for high-yielding peanut cultivation in high-latitude areas. However, there is limited field data about how exogenous calcium (Ca2+) application would improve peanut growth resilience during exposure to chilling stress at early sowing (ES). To help address this problem, a two-year field study was conducted to assess the effects of exogenous foliar Ca2+ application on photosynthetic carbon fixation and pod yield in peanuts under different sowing scenarios. We measured plant growth indexes, leaf photosynthetic gas exchange, photosystems activities, and yield in peanuts. It was indicated that ES chilling stress at the peanut seedling stage led to the reduction of Pn, gs, Tr, Ls, WUE, respectively, and the excessive accumulation of non-structural carbohydrates in leaves, which eventually induced a chilling-dependent feedback inhibition of photosynthesis due mainly to weaken growth/sink demand. While exogenous Ca2+ foliar application improved the export of nonstructural carbohydrates, and photosynthetic capacity, meanwhile activated cyclic electron flow, thereby enhancing growth and biomass accumulation in peanut seedlings undergoing ES chilling stress. Furthermore, ES combined with exogenous Ca2+ application can significantly enhance plant chilling resistance and peanut yield ultimately in the field. In summary, the above results demonstrated that exogenous foliar Ca2+ application restored the ES-linked feedback inhibition of photosynthesis, enhancing the growth/sink demand and the yield of peanuts.

The sweet potato transcription factor IbbHLH33 enhances chilling tolerance in transgenic tobacco

Chilling is an important abiotic stress in plants. Sweet potato is sensitive to cold damage due to its tropical origin. In this study, we identified a basic helix-loop-helix (bHLH) gene, IbbHLH33, from our cold-tolerance-related transcriptomic data. Further analyses revealed that IbbHLH33 encoded a nuclear protein and was most closely related to AtbHLH33. RT-qPCR analysis showed that IbbHLH33 was expressed at the highest level in the roots, and its expression was strongly induced by low temperature (4 °C), H<sub>2</sub>O<sub>2</sub> and abscisic acid (ABA) treatments. Transgenic tobacco plants overexpressing IbbHLH33 were obtained by Agrobacterium-mediated transformation, which enhanced the chilling resistance of tobacco. At low temperatures, the proline content, superoxide dismutase (SOD) activity and malondialdehyde (MDA) content increased significantly, while the relative conductivity decreased significantly. At the same time, the expression of proline synthesis related genes and antioxidant activity related genes increased, while the expression of ABA synthesis related genes decreased. The results showed that IbbHLH33 is a transcription factor encoding a gene of the bHLH family that regulates chilling tolerance. In conclusion, these data suggest that IbbHLH33 has the potential to improve chilling tolerance in tobacco and other plants.

Coronatine Enhances Chilling Tolerance of Tomato Plants by Inducing Chilling-Related Epigenetic Adaptations and Transcriptional Reprogramming.

Low temperature is an important environmental factor limiting the widespread planting of tropical and subtropical crops. The application of plant regulator coronatine, which is an analog of Jasmonic acid (JA), is an effective approach to enhancing crop’s resistance to chilling stress and other abiotic stresses. However, the function and mechanism of coronatine in promoting chilling resistance of tomato is unknown. In this study, coronatine treatment was demonstrated to significantly increase tomato chilling tolerance. Coronatine increases H3K4me3 modifications to make greater chromatin accessibility in multiple chilling-activated genes. Corresponding to that, the expression of CBFs, other chilling-responsive transcription factor (TF) genes, and JA-responsive genes is significantly induced by coronatine to trigger an extensive transcriptional reprogramming, thus resulting in a comprehensive chilling adaptation. These results indicate that coronatine enhances the chilling tolerance of tomato plants by inducing epigenetic adaptations and transcriptional reprogramming.

NMR revealed that trehalose enhances sucrose accumulation and alleviates chilling injury in peach fruit

• Trehalose alleviates the effects of chilling injury in peach fruit • NMR reveals higher sucrose content in trehalose treated peaches • Trehalose treatment decreases expression of SnRK1, promoting the accumulation of sucrose • Trehalose improves the cold tolerance of peach by affecting sucrose levels Nuclear magnetic resonance (NMR) was applied to identify the metabolic differences in trehalose-treated and -untreated peach fruit during storage at 5°C in this study. Forty-one metabolites were identified using NMR; trehalose-treated peaches had higher sucrose, proline, and choline content, and lower glucose, fructose and gluconic acid content. These metabolic changes were accompanied by lower levels of chilling injury (CI). Trehalose-treated fruit had lower levels PpSnRK1 expression, resulting in lower sucrose decomposition and higher sucrose synthesis. We suggest that accumulated sucrose in trehalose-treated peaches is associated with the decrease in expression of PpSnRK1 and increases in the expression and activity of the sucrose phosphate synthase (SPS). This probably results in the improvement of chilling resistance in peach fruit.

Polyamines in plasma membrane function in melatonin-mediated tolerance of apricot fruit to chilling stress

Polyamines are closely associated with environmental stresses and melatonin pretreatment enhances the resistance of fruit to chilling stress. However, a mechanism underlying melatonin-mediated chilling resistance remains to be answered. This research aimed to illuminate whether polyamines would be involved in melatonin-mediated chilling resistance. Therefore, in the experiment, the polyamines conjugated to the plasma membrane from the melatonin-pretreated apricot flesh cell were examined under chilling stress. Chilling resistance was judged by four parameters: fruit browning degree, plasma membrane permeability, malondialdehyde content and plasma membrane protein sulfhydryl level. Results showed melatonin pretreatment led to obvious rises in the levels of non-covalently conjugated spermine and spermidine, and covalently conjugated putrescine and spermidine in the plasma membrane. Methylglyoxyl-bis (guanylhydrazone) pretreatment could inhibit the melatonin-induced increases of non-covalently conjugated spermidine and spermine by inhibiting S-adenosylmethionine decarboxylase (SAMDC) activity and free spermidine and spermine contents in flesh, coupled with the decrease in chilling resistance. Similarly, phenanthroline pretreatment could inhibit the melatonin-induced increases in covalently conjugated putrescine and spermidine in the plasma membrane through inhibiting transglutaminase (TGase) activity and simultaneously could aggravate chilling damage. The results suggested melatonin pretreatment could enhance chilling resistance by increasing non-covalently conjugated spermidine and spermine, as well as covalently conjugated putrescine and spermidine in the plasma membrane of apricot fruit.