Inositol 1,4,5-Trisphosphate Mediates Nitric-Oxide-Induced Chilling Tolerance and Defense Response in Postharvest Peach Fruit

SlbHLH1 mediates ABA treatment-retarded chilling injury by repressing SlPP2C29 in tomato fruit

Low-temperature storage can facilitate to the preservation of postharvest fruits. However, tomato fruit are vulnerable to chilling injury (CI) throughout refrigerated storage, resulting in economic losses. Abscisic acid (ABA) treatment weakened the CI progression in tomato fruit. Protein phosphatase 2 C 29 (SlPP2C29) acted as the negative regulator in the ABA-enhanced chilling tolerance. The gene expression of SlPP2C29 and activity of PP2C were down regulated by ABA treatment. Furthermore, SlPP2C29 was shown to be the negative downstream messenger in the ABA-alleviated oxidative damage. Moreover, basic helix-loop-helix 1 (SlbHLH1) bound to the E-box element within SlPP2C29 promoter, and negatively modulated its expression. SlbHLH1 mediated the ABA-boosted chilling tolerance. It turned out that SlbHLH1 was the positive modulator involved in the ABA-inhibited SlPP2C29 expression and PP2C activity. SlbHLH1 was furtherly found to work as the positive regulator in the ABA-lowered oxidative damage. Thus, SlbHLH1 alleviated the CI severity by repressing SlPP2C29 under ABA treatment in tomato fruit.

PpMYB105 inhibits chilling injury by regulating PpMsrA1 in peach fruit

KEY MESSAGE

MeJA supplementation enhanced the chilling tolerance and gene expression of PpMsrA1. PpMYB105 protein positively regulated the PpMsrA1 promoter. PpMYB105 mediated the MeJA-boosted chilling tolerance by regulating PpMsrA1. Cold storage can maintain the quality of postharvest fruit. However, peaches easily suffer from chilling injury (CI) during cold storage, leading to economic loss. Results showed that methyl jasmonate (MeJA) supplementation reduced the CI severity, and enhanced the gene expression of methionine sulfoxide reductase A1 (PpMsrA1). It was found that MeJA application elevated the MsrA activity and methionine (Met) content, and reduced the methionine-S-sulfoxide (Met-S-SO) content and reactive oxygen species (ROS) production afterwards. Moreover, PpMYB105 could activate the transcription of PpMsrA1 by binding to the MYB binding element in its promoter. The gene expression of PpMYB105 was up-regulated by MeJA application. Overexpression of PpMYB105 in tomatoes enhanced the chilling tolerance and gene expression of SlMsrA1. Virus-induced gene silencing of PpMYB105 in peaches resulted in the increase in CI severity and the decrease in gene expression of PpMsrA1. Thus, PpMYB105 was involved in the MeJA-boosted chilling tolerance by regulating PpMsrA1.

DNP and ATP regulate the breakdown occurrence in the pulp of Phomopsis longanae Chi-infected longan fruit through modulating the metabolism of membrane lipid

This study aimed to illustrate how DNP and ATP affected the pulp breakdown occurrence in P. longanae-infected longan and their relationship with the membrane lipid metabolism. Compared with P. longanae-inoculated samples, the pulp of DNP-treated P. longanae-infected longan exhibited higher cellular membrane permeability, breakdown index, activities of PI-PLC, PLD, PC-PLC, LOX, and lipase, and values of SFAs, PA, and DAG, while lower levels of PI, PC, USFAs, IUFA and U/S. However, the opposite findings were observed in ATP-treated P. longanae-infected longan. The data manifested that DNP-increased the pulp breakdown occurrence in P. longanae-inoculated samples was due to the elevated MLDEs activities that reduced the contents of phospholipids (PI, PC) and USFAs, disrupting the cell membrane structures. Nevertheless, ATP decreased the pulp breakdown occurrence in P. longanae-inoculated samples, which was ascribed to the reduced MLDEs activities that raised phospholipids (PI, PC) and USFAs contents, thus maintaining the cell membrane structures.

Nitric oxide modulates folate-mediated one-carbon metabolism and mitochondrial energy levels of peaches during cold storage

Folate-mediated one-carbon metabolism (FOCM) is closely associated with postharvest preservation. This study investigated the effects of exogenous nitric oxide (NO) on FOCM, storage quality, energy metabolism, and mitochondrial membrane integrity in cold-storage peach fruit. In this experiment, peaches were soaked with 1.5 mmol L^-1S-nitrosoglutathione (GSNO) as NO donor, and the negative treatment (NT) solution containing 5 μmol L^-1 carboxy-PTIO (c-PTIO, NO scavenger), 200 μmol L^-1 N^G-Nitro-_L-arginine methyl ester (_L-NAME, NO synthase-like enzyme inhibitor), and 200 μmol L^-1 sodium tungstate dihydrate (nitrate reductase inhibitor) and stored at 0°C. The results showed that NO decreased the activity of S-adenosylmethionine synthase and S-adenosylhomocysteine hydrolase and increased the activity of methionine sulfoxide reductase A, as well as the content of N5-methyl-THF, the ratio of tetrahydrofolate (THF), homocysteine, methionine, S-adenosylmethionine (SAM), and SAM to S-adenosylhomocysteine compared with the control, indicating that NO effectively increased FOCM flux by affecting the activity of FOCM enzymes. Meanwhile, NO increased the activities of H⁺-ATPase, Ca²⁺-ATPase, cytochrome c oxidase, succinate dehydrogenase, and the contents of adenosine triphosphate and adenosine diphosphate, and maintained high energy charge in peaches during storage. NO retarded the increase in mitochondrial permeability transition, reactive oxygen species content, and the decrease in mitochondrial membrane fluidity, membrane potential, and swelling. NT treatment exhibited the opposite results. In conclusion, these results suggested that NO could induce the accumulation of folate and FOCM flux and maintain mitochondrial energy levels, which might be responsible for maintaining the quality of peaches during cold storage.

Proteomic and metabolomic studies on chilling injury in peach and nectarine

Peaches and nectarines are temperate climate stone fruits, which should be stored at 0°C to prevent the ripening of these climacteric fruits. However, if stored for too long or if stored at a higher temperature (4 or 5°C), they develop chilling injury. Chilling injury damage includes (1) dry, mealy, wooly (lack of juice) fruits, (2) hard-textured fruits with no juice (leatheriness), (3) flesh browning, and (4) flesh bleeding or internal reddening. There are genetic components to these disorders in that early season fruits are generally more resistant than late season fruits, and white-fleshed fruits are more susceptible to internal browning than yellow-fleshed fruits. A recent review covered the recent research in genomic and transcriptomic studies, and this review examines findings from proteomic and metabolomics studies. Proteomic studies found that the ethylene synthesis proteins are decreased in cold compromised fruits, and this affects the processes initiated by ethylene including cell wall and volatile changes. Enzymes in metabolic pathways were both higher and lower in abundance in CI fruits, an indication of an imbalance in energy production. Stress proteins increased in both fruits with or without CI, but were higher in damaged fruits. Metabolomics showed the role of levels of sugars, sucrose, raffinose, galactinol, and glucose-6-phosphate in protection against chilling injury, along with other membrane stabilizers such as polyamines. Amino acid changes were inconsistent among the studies. Lipid species changes during storage could be correlated with sensitivity or resistance to CI, but more studies are needed.

Calcium Mediated Cold Acclimation in Plants: Underlying Signaling and Molecular Mechanisms

Exposure of plants to low temperatures adversely affects plant growth, development, and productivity. Plant response to cold stress is an intricate process that involves the orchestration of various physiological, signaling, biochemical, and molecular pathways. Calcium (Ca²⁺) signaling plays a crucial role in the acquisition of several stress responses, including cold. Upon perception of cold stress, Ca²⁺ channels and/or Ca²⁺ pumps are activated, which induces the Ca²⁺ signatures in plant cells. The Ca²⁺ signatures spatially and temporally act inside a plant cell and are eventually decoded by specific Ca²⁺ sensors. This series of events results in the molecular regulation of several transcription factors (TFs), leading to downstream gene expression and withdrawal of an appropriate response by the plant. In this context, calmodulin binding transcription activators (CAMTAs) constitute a group of TFs that regulate plant cold stress responses in a Ca²⁺ dependent manner. The present review provides a catalog of the recent progress made in comprehending the Ca²⁺ mediated cold acclimation in plants.

Nitric oxide regulation of plant metabolism

Nitric oxide (NO) has emerged as an important signal molecule in plants, having myriad roles in plant development. In addition, NO also orchestrates both biotic and abiotic stress responses, during which intensive cellular metabolic reprogramming occurs. Integral to these responses is the location of NO biosynthetic and scavenging pathways in diverse cellular compartments, enabling plants to effectively organize signal transduction pathways. NO regulates plant metabolism and, in turn, metabolic pathways reciprocally regulate NO accumulation and function. Thus, these diverse cellular processes are inextricably linked. This review addresses the numerous redox pathways, located in the various subcellular compartments that produce NO, in addition to the mechanisms underpinning NO scavenging. We focus on how this molecular dance is integrated into the metabolic state of the cell. Within this context, a reciprocal relationship between NO accumulation and metabolite production is often apparent. We also showcase cellular pathways, including those associated with nitrate reduction, that provide evidence for this integration of NO function and metabolism. Finally, we discuss the potential importance of the biochemical reactions governing NO levels in determining plant responses to a changing environment.

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

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 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.

Employing phytosulfokine α (PSKα) for delaying broccoli florets yellowing during cold storage

The yellowing of florets limits the economic and nutritional value of broccoli during postharvest. We investigated mechanisms of action of 150 nM phytosulfokine α (PSKα) for delaying florets yellowing in broccoli during cold storage. Our results showed that SUMO E3 ligase (SIZ1) gene expression was higher in florets treated with PSKα, which may prevent endogenous H₂O₂ accumulation, resulting from the higher activity of superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase. Besides, higher expression of methionine sulfoxide reductase and cysteine peroxiredoxin genes, concomitant with higher expression of heat shock proteins 70/90 genes, may arise from higherexpression of SIZ1 gene. Lower expression and activity of phospholipase D and lipoxygenase may be liable for membrane integrity protection featured by lower malondialdehyde accumulation in florets treated with PSKα. Additionally,florets treated with PSKα exhibited higher endogenous cytokinin accumulation which may arise from higher expression of isopentenyl transferase gene, concomitant with lower expression of cytokinin oxidase gene.

GhPIPLC2D promotes cotton fiber elongation by enhancing ethylene biosynthesis

Inositol-1,4,5-trisphosphate (IP₃) is an important second messenger and one of the products of phosphoinositide-specific phospholipase C (PIPLC)-mediated phosphatidylinositol (4,5) bisphosphate (PIP₂) hydrolysis. However, the function of IP₃ in cotton is unknown. Here, we characterized the function of GhPIPLC2D in cotton fiber elongation. GhPIPLC2D was preferentially expressed in elongating fibers. Suppression of GhPIPLC2D transcripts resulted in shorter fibers and decreased IP₃ accumulation and ethylene biosynthesis. Exogenous application of linolenic acid (C18:3) and phosphatidylinositol (PI), the precursor of IP₃, improved IP₃ and myo-inositol-1,2,3,4,5,6-hexakisphosphate (IP₆) accumulation, as well as ethylene biosynthesis. Moreover, fiber length in GhPIPLC2D-silenced plant was reduced after exogenous application of IP₆ and ethylene. These results indicate that GhPIPLC2D positively regulates fiber elongation and IP₃ promotes fiber elongation by enhancing ethylene biosynthesis. Our study broadens our understanding of the function of IP₃ in cotton fiber elongation and highlights the possibility of cultivating better cotton varieties by manipulating GhPIPLC2D in the future.

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GhPIPLC2D positively regulates cotton fiber elongation

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GhPIPLC2D cleaves PIP₂ into IP₃, which could be phosphorylated to IP₆

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IP₆ enhances fiber elongation via improving ethylene biosynthesis

Exogenous glutathione alleviates chilling injury in postharvest bell pepper by modulating the ascorbate-glutathione (AsA-GSH) cycle

We investigated the effect of exogenous glutathione (GSH) on chilling injury (CI) in postharvest bell pepper fruits stored at low temperature and explored the mechanism of this treatment from the perspective of the ascorbate-glutathione (AsA-GSH) cycle. Compared with the control, fruits treated with exogenous GSH before refrigeration displayed only slight CI symptoms and mitigated CI-induced cell damage after 10 d. Moreover, the treated peppers had lower lipid peroxidation product, H₂O₂, and O₂^- content than those did the control. Glutathione treatment enhanced the ascorbate-glutathione cycle by upregulating CaAPX1, CaGR2, CaMDHAR1, and CaDHAR1 and the antioxidant enzymes APX, GR, and MDHAR associated with the ascorbate-glutathione cycle. Glutathione treatment also increased ascorbate and glutathione concentrations. Taken together, our results showed that exogenous GSH treatment could alleviate CI in pepper fruits during cold storage by triggering the AsA-GSH cycle and improving antioxidant capacity.

Nitric oxide: A radical molecule with potential biotechnological applications in fruit ripening

Nitric oxide (NO) is a short-life and free radical molecule involved in a wide range of cellular, physiological and stressful processes in higher plants. In recent years it has been observed that exogenous NO application can palliate adverse damages against abiotic and biotic stresses. Conversely, there is accumulating information indicating that endogenous NO participates significantly in the mechanism of modulation of the ripening in climacteric and non-climacteric fruits. Even more, when NO is exogenously applied, it can mediate beneficial effects during ripening and postharvest storage being one of the main effects the increase of antioxidant systems. Consequently, NO could be a promising biotechnological tool to improve crops through ameliorating nutritional indexes and to alleviate damages during fruit ripening and postharvest management. Thus, this approach should be complementary to previous strategies to allow preserving the quality and healthiness of fruits with a view of enhancing their added value. The present mini-review aims to provide an overview of NO biochemistry in plants and updated information on the relevance of NO in fruit ripening and postharvest stages with a view to its biotechnological applications.

Combining salicylic acid and trisodium phosphate alleviates chilling injury in bell pepper (Capsicum annuum L.) through enhancing fatty-acid desaturation efficiency and water retention

Chilling injury (CI) restricts the quality and shelf life of bell pepper fruits; reducing these CI-induced detrimental effects is therefore of high economic and agricultural relevance. Here, we investigated the effects of trisodium phosphate (TSP), salicylic acid (SA), and TSP + SA treatments on pepper fruits under cold stress at 4 °C for 25 d. Combined TSP + SA treatment performed an optimal effect. Specifically, TSP + SA treatment enhanced fatty-acid desaturation efficiency, as indicated by the increased expression of key fatty acid desaturase genes, and higher content of unsaturated fatty acids. Meanwhile, TSP + SA treatment inhibited the CI-induced membrane damage, manifested as lower electrolyte leakage and malondialdehyde content. Furthermore, low field-nuclear magnetic resonance and proline content also revealed that TSP + SA treatment mitigated CI through enhancing water retention in pepper fruits. Collectively, our results may shed new light on optimizing the low-temperature storage conditions of post-harvest peppers.

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.

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.