Chilling Injury Of Banana Fruit Research Articles

The metabolism of membrane lipid participates in the occurrence of chilling injury in cold-stored banana fruit

Banana fruit is highly vulnerable to chilling injury (CI) during cold storage, which results in quality deterioration and commodity reduction. The purpose of this study was to investigate the membrane lipid metabolism mechanism underlying low temperature-induced CI in banana fruit. Chilling temperature significantly induced CI symptoms in banana fruit, compared to control temperature (22 °C). Using physiological experiments and transcriptomic analyses, we found that chilling temperature (7 °C) increased CI index, malondialdehyde content, and cell membrane permeability. Additionally, chilling temperature upregulated the genes encoding membrane lipid-degrading enzymes, such as lipoxygenase (LOX), phospholipase D (PLD), phospholipase C (PLC), phospholipase A (PLA), and lipase, but downregulated the genes encoding fatty acid desaturase (FAD). Moreover, chilling temperature raised the activities of LOX, PLD, PLC, PLA, and lipase, inhibited FAD activity, lowered contents of unsaturated fatty acids (USFAs) (γ-linolenic acid and linoleic acid), phosphatidylcholine, and phosphatidylinositol, but retained higher contents of saturated fatty acids (SFAs) (stearic acid and palmitic acid), free fatty acids, phosphatidic acid, lysophosphatidic acid, diacylglycerol, a lower USFAs index, and a lower ratio of USFAs to SFAs. Together, these results revealed that chilling temperature-induced chilling injury of bananas were caused by membrane integrity damage and were associated with the enzymatic and genetic manipulation of membrane lipid metabolism. These activities promoted the degradation of membrane phospholipids and USFAs in fresh bananas during cold storage.

Transcriptional repression of MaRBOHs by MaHsf26 is associated with heat shock-alleviated chilling injury in banana fruit

Both heat shock factors (Hsfs) and reactive oxygen species (ROS) are widely perceived to be involved in chilling stress response. However, the particular mechanism of Hsfs mediated-ROS metabolism related to chilling stress remains largely unknown, especially during chilling injury development of postharvest economically cold-sensitive fruit such as banana. In this study, we found that heat shock treatment (HST) could effectively alleviate postharvest banana chilling injury and reduce ROS accumulation during storage. The expression levels of several respiratory burst oxidase homolog (RBOH) genes, encoding ROS-producing enzymes, increased consistently with the progression, whereas were inhibited upon HST. Significantly, we identified an Hsfs MaHsf26, which exhibited a opposite expression pattern as that of MaRBOHs, as the putative binding protein of MaRBOHB-like1, MaRBOHE-like and MaRBOHF-like promoters using yeast one-hybrid (Y1H) screening analysis. Further electrophoretic mobility shift assay (EMSA) and dual luciferase reporter (DLR) analysis displayed MaHsf26 suppressed the transcriptions of MaRBOHB-like1, MaRBOHE-like and MaRBOHF-like through binding to the heat shock elements (HSE) in their promoters, respectively. In general, our results suggested that MaHsf26 plays as a transcriptional repressor of ROS generation by suppressing the transcriptions of MaRBOHs and thereby involving in the HST-mitigated chilling injury in postharvest banana fruit.

Comparative transcriptomic analysis reveals the potential mechanism of hot water treatment alleviated-chilling injury in banana fruit

Banana fruit is prone to chilling injury (CI) during cold storage, resulting in quality deterioration and commodity reduction. The hot water treatment (HWT), dipping banana fruit in hot water (52 °C) for 3 min, reduced CI symptom at 7 °C storage. The purpose of this study was to investigate the potential molecular mechanism of HWT on the alleviation of CI of postharvest banana fruit. It was found that HWT treatment obviously inhibited the increases in CI index, relative electrolytic leakage, and the contents of malonaldehyde (MDA) and O2•-, while enhanced proline accumulation. Further transcriptome analysis in the pericarp of banana fruit was evaluated during storage. The results showed that differentially expressed genes (DEGs) in the comparison between control and HWT group were mainly enriched in photosynthesis, chlorophyll metabolism, lipid metabolism, glutathione metabolism, and brassinosteroid and carotenoid biosynthesis. Moreover, transcriptome expression profiles and RT-qPCR analyses exhibited that the corresponding genes involved in these metabolism pathways and heat shock proteins (HSPs) were upregulated by HWT during cold storage. In general, our findings clearly reveal the potential pathways by which HWT alleviates CI in banana fruit, enriching the theoretical basis for the application of hot water to reduce CI in fruits.

Specific binding of NTP to MaDORN1.19 enhances cold tolerance of postharvest banana fruit during storage

As the first plant receptor gene for extracellular ATP (eATP), DORN1, could play a key role in responding low temperature in plants. This study investigated the interactions of the banana receptor, MaDORN1.19, with nucleoside triphosphates (NTPs) to affect chilling injury (CI) of banana fruit stored for 8 d at 6 °C. Molecular simulation found that ATP or GTP exhibited more stable interactions with MaDORN1.19 according to the lower libDOCK scores and more amino acid residues in binding pockets compared with CTP and UTP. Results indicated that the CI indices of ATP or GTP-treated banana fruit were 1.6 and 1.79 whereas those of UTP or CTP-treated and non-treated fruit were 2.11, 2.07 and 2.22, respectively. Furthermore, application of ATP or GTP significantly maintained a low level of eATP, inhibited the accumulation of malondialdehyde and enhanced the antioxidant ability of banana fruit during cold storage. Based on the CI extent, binding ability of NTP to MaDORN1.19 and the NTP treatment effect, it can be suggested that ATP or its analogs could specifically bind to MaDORN1.19 to maintain eATP homeostasis, retard oxidative damage, ensure membrane integrity and, thus, attenuate chilling injury of banana fruit during cold storage. This study provided new insights of eATP in the CI occurrence of banana fruit during storage at low temperature.

Brassinolide alleviated chilling injury of banana fruit by regulating unsaturated fatty acids and phenolic compounds

The effects of brassinolide (BL) on alleviating the occurrence of chilling injury (CI) of banana fruit were investigated. The present results showed that BL effectively decreased the CI index, enhanced the proline accumulation, reduced the malondialdehyde production, and accelerated starch degradation. Meanwhile, it also enhanced the activities of antioxidative enzymes and contents of the phenolic compounds, and decreased the reactive oxygen species accumulation. Higher integrity of plasma membrane was observed in the epidermal tissues and higher levels of unsaturated fatty acids were detected in the membrane, indicated that BL enhanced membrane lipid fluidity and maintained the cell membrane integrity of banana fruit. In conclusion, BL treatment is a potential method in enhancing chilling tolerance of banana fruit under low temperature storage or cold chain circulation.

Changes of Morphology, Chemical Compositions, and the Biosynthesis Regulations of Cuticle in Response to Chilling Injury of Banana Fruit During Storage.

The plant cuticle covers almost all the outermost surface of aerial plant organs, which play a primary function in limiting water loss and responding to the environmental interactions. Banana fruit is susceptible to thermal changes with chilling injury below 13°C and green ripening over 25°C. Herein, the changes of surface morphology, chemical compositions of cuticle, and the relative expression of cuticle biosynthesis genes in banana fruit under low-temperature storage were investigated. Banana fruit exhibited chilling injury rapidly with browned peel appearance stored at 4°C for 6 days. The surface altered apparently from the clear plateau with micro-crystals to smooth appearance. As compared to normal ones, the overall coverage of the main cuticle pattern of waxes and cutin monomers increased about 22% and 35%, respectively, in browned banana stored under low temperature at 6 days. Fatty acids (C16–C18) and ω-OH, mid-chain-epoxy fatty acids (C18) dominated cutin monomers. The monomers of fatty acids, the low abundant ω, mid-chain-diOH fatty acids, and 2-hydroxy fatty acids increased remarkably under low temperature. The cuticular waxes were dominated by fatty acids (> C19), n-alkanes, and triterpenoids; and the fatty acids and aldehydes were shifted to increase accompanied by the chilling injury. Furthermore, RNA-seq highlighted 111 cuticle-related genes involved in fatty acid elongation, biosynthesis of very-long-chain (VLC) aliphatics, triterpenoids, and cutin monomers, and lipid-transfer proteins were significantly differentially regulated by low temperature in banana. Results obtained indicate that the cuticle covering on the fruit surface was also involved to respond to the chilling injury of banana fruit after harvest. These findings provide useful insights to link the cuticle on the basis of morphology, chemical composition changes, and their biosynthesis regulations in response to the thermal stress of fruit during storage.

Attenuation of postharvest peel browning and chilling injury of banana fruit by Astragalus polysaccharides

The effect of Astragalus polysaccharides (APS) on peel browning and chilling injury (CI) of banana fruit was investigated. The results showed that APS induced the activities of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and reactive oxygen species (ROS) scavenging, reduced the H2O2 accumulation and the membrane lipid peroxidation and electrolyte leakage, by which delayed fruit CI, alleviated peel browning and the loss of nutrients in the flesh. It also improved the antioxidant capacity of fruit, enhanced the expression of MaSOD, MaCAT, MaAPX and led to the increase of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) activities. Moreover, APS up-regulated the expression of MaPOD, MaPAL, MaCHS and down-regulated the expression of MaPPO, resulting in the composition changes of the phenolics and flavonoids in banana fruit. Higher levels of hesperidin, ferulic acid, acacetin and myricetin were detected in APS treated fruit and were involved in alleviating fruit CI and peel browning. The present results for the first time demonstrated that APS treatment alleviated the CI of banana fruit, and provided a promising strategy for enhancing postharvest chilling tolerance.

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.

Ethylene attenuates chilling injury of banana fruit via the MabHLH060/183 module in controlling phosphatidic acid formation genes

Chilling injury (CI) of banana represents a serious problem constraining postharvest preservation in the industry. Application of ethylene was found to efficiently attenuate CI of banana, however, the mechanism of which remains to be investigated. Here, we found that application of ethrel could ameliorate the CI of banana, as evidenced by lower CI index, electrolytic leakage and malondialdehyde content. Meanwhile, expression of phosphatidic acid (PA) formation genes MaPLDδ1, MaPLDδ5 and MaDGK2, as well as two transcriptional regulators MabHLH060 and MabHLH183 was significantly increased with the progression of CI, but decreased under ethrel treatment. MabHLH060 and MabHLH183 were shown to locate in nucleus and have transactivation ability. Importantly, these two transcriptional regulators MabHLH060/183 recognized the E-box elements in the promoters of MaPLDδ1, MaPLDδ5 and MaDGK2, and promoted their transcription. Together, these findings suggest that ethylene-alleviated CI of banana may involve the MabHLH060/183 module in modulating the expression of PA formation genes.

Melatonin enhanced chilling tolerance and alleviated peel browning of banana fruit under low temperature storage

The effect of melatonin on chilling injury of banana fruit was investigated. Results showed that melatonin treatment delayed chilling injury and alleviated peel browning. Melatonin treatment increased the contents of phospholipids and unsaturated fatty acid, induced the reactive oxygen species (ROS) scavenging enzyme activities, and reduced the contents of H2O2, O2– of banana fruit. It also induced the miR528 expression, resulting in the down expression of the potential target genes of MaPPO1, MaPPO2 and MaPPO3, and inhibited the PPO activities. Moreover, the phenolic compounds in melatonin treated banana fruit peel were quantitatively analyzed by liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results indicated that melatonin treatment changed the contents of 63 polyphenolics in banana fruit, and by which involved in delaying chilling injury and alleviating peel browning. In conclusion, melatonin treatment is a potential technique in alleviating chilling injury of banana fruit under low temperature storage.

Regulatory influences of methyl jasmonate and calcium chloride on chilling injury of banana fruit during cold storage and ripening.

Fruit quality is preserved through cold storage, but climacteric fruits are prone to chilling injury (CI) which limits their shelf life and marketability. Two postharvest treatments, 1 mM methyl jasmonate (MeJA) and 4% (wt/vol) calcium chloride (Ca2+), were separately used to investigate their influences on chilling injury (CI) incidence and fruit quality in unpacked banana cultivar “Grand Nain” during cold storage and subsequent ripening. Banana fruits were dipped for 2 min in aqueous emulsions containing 1% Tween‐80—used here as a surfactant with untreated fruits being used as control. Fruits were stored at 10 ± 2 or optimal 14 ± 2°C temperature and relative humidity 85%–90% for a 20‐day cold storage period and then removed from cold storage at 5, 10, 15, and 20 days followed by ripening at 22 ± 2°C. Treatments with MeJA or Ca2+ significantly reduced CI in banana fruit during cold storage and subsequent ripening temperature. Untreated controls exhibited increased CI, weight loss, and decreased hue angle, as well as firmness. In contrast, the aforementioned changes were considerably delayed after treatments with MeJA or Ca2+. Application of MeJA or Ca2+ also increased total phenolic compound contents and maintenance of total antioxidant activity throughout cold storage and during ripening periods as compared to that of the control. These findings indicate that coating bananas with 1 mM MeJA or 4% (wt/vol) Ca2+ can improve the postharvest quality and shelf life of fruits, and it can ameliorate chilling injury during cold storage and at ripening temperature.

Characterization and function of banana DORN1s during fruit ripening and cold storage

Abstract DORN1 as the first plant receptor gene for extracellular ATP (eATP) regulates a series of biological activities, but the biological roles of eATP and DORN1 remain unclear in postharvest fruit. In this study, a total of 34 DORN1s termed as MaDORN1s were identified from banana genome and can be classified into five groups according to the analyses of phylogenetic tree, gene structure and conserved domain. The cis-element and microRNA targeting analyses also revealed that MaDORN1s might regulate ripening process and cold stress response. Using the molecular docking, the ten highly expressed MaDORN1 proteins exhibited high binding affinities with ATP, indicating the key interaction sites between MaDORN1 proteins and ATP. It was noted particularly that the pretreatment with 1 mM ATP for 5 min significantly promoted fruit ripening and enhanced cold tolerance of postharvest banana during storage. The eATP treatment induced rapidly the early expressions of most MaDORN1s in association with accelerated ripening at ambient temperature while inhibited the initial expressions in relation to reduced chilling injury of banana fruit at low temperature, suggesting their early responses in fruit ripening and low temperature storage. This study provides important insights into the roles of eATP and its receptor DORN1 of banana fruit during ripening and in response to low temperature.

Exogenous progesterone treatment alleviates chilling injury in postharvest banana fruit associated with induction of alternative oxidase and antioxidant defense

The effects of exogenous progesterone (PROG) on chilling injury (CI) in postharvest banana fruit were investigated. Concentration screening tests showed that 10−5 mol/l PROG was most effective in reducing CI in banana fruit stored for 25 d at 5 ± 1 °C, but did not markly increase PROG content of pulps. This PROG treatment significantly reduced the electrolyte leakage, levels of malondialdehyde, O2− production rate and H2O2 contents in banana compared with control fruit. The PROG treatment caused an early induction of alternative oxidase (AOX) at the transcript and protein level to reduce the generation of O2− and H2O2. PROG treatment also enhanced the transcript levels and activities of antioxidant enzymes and maintained higher levels of reduced glutathione and ascorbic acid than the control fruit. These results suggested that PROG attenuating CI in banana fruit may be attributed to the induction of AOX and the improvement of enzyme and non-enzymatic antioxidant defenses.

Fibroin treatment inhibits chilling injury of banana fruit via energy regulation

The effects of fibroin on chilling tolerance of harvested banana fruit via energy regulation were investigated after 4 d of storage at 6 °C. Chilling injury index, respiration rate and electrolyte leakage were also investigated. Application of 1 g L−1 fibroin solution reduced effectively chilling injury symptoms and delayed significantly the decreases in ATP level and energy charge (EC) of banana fruit during storage at 6 °C. Compared with the control group, the transcriptional level of MaATPase1 and MaAAC1 were up-regulated while MaAOX1 and MaUCP1 were down-regulated in fibroin-treated banana fruit after 4 d of storage. Meanwhile, fibroin treatment increased the contents of soluble sugars. The results suggested that fibroin treatment exhibited the potential for alleviating chilling injury symptoms of banana fruit during cold storage by maintaining high energy status.

Proteomic profiling of 24-epibrassinolide-induced chilling tolerance in harvested banana fruit

The mechanism of 24-epibrassinolide (EBR)-induced chilling tolerance in harvested banana fruit was investigated. Results showed that EBR pretreatment remarkably suppressed the development of chilling injury (CI) in harvested banana fruit during 12 days of cold storage at 8 °C, as indicated by lower CI index in treated fruit. Physiological measurements exhibited that EBR treatment reduced the relative electrolyte leakage and malondialdehyde (MDA) content while increased the chlorophyll fluorescence (Fv/Fm), total soluble solids (TSS) and ratio of TSS and titratable acidity. Furthermore, the differentially accumulated proteins of banana fruit in response to EBR and cold treatment were investigated by employing gel-based proteomic in combination with MALDI-TOF-TOF MS and LC-ESI-MS/MS analyses. There were fifty five protein spots to be successfully identified. Notably, most of up-regulated proteins by EBR treatment were related to energy biosynthesis, stress response and cell wall modification. In contrast, proteins involved in protein degradation and energy consumption were down-regulated by EBR treatment. These results suggest that EBR treatment could enhance the defense ability, promote the synthesis and utilization of energy, as well as maintain the protein function via enhancing protein biosynthesis and inhibiting protein degradation, consequently contributing to improvement of cold tolerance in harvested banana fruit. SignificanceTo extend our understanding of chilling injury (CI) of harvested banana fruit, we reported the effect of 24-epibrassinolide (EBR) on CI of banana fruit when stored at 8 °C. It was the first report on the comprehensive proteomic analysis of banana fruit in response to EBR treatment at low temperature. EBR pretreatment significantly reduced CI in harvested banana fruit. Fifty five protein spots were successfully identified. Notably, the most of up-regulated proteins by EBR treatment were related to energy biosynthesis, stress response and cell wall modification. In contrast, proteins involved in protein degradation and energy consumption were down-regulated. These results suggest that exogenous EBR treatment could enhance the defense ability and maintain high energy status. Meanwhile, EBR treatment maintained protein function via enhancing protein biosynthesis and inhibiting protein degradation. These results may help us to understand the molecular mechanism of the chilling tolerance induced by EBR treatment and broaden the current knowledge of the mechanism of CI of harvested banana fruit.

Antioxidant enzyme activities and exogenous ascorbic acid treatment of ‘Williams’ banana during long-term cold storage stress

Abstract The effect of exogenous ascorbic acid (AA) application on chilling injury (CI) of banana fruit ‘Williams’ (Giant Cavendish AAA sub-group) harvested at the mature green stage. The investigation aimed to increase chilling tolerance of banana fruits under cold storage temperature. The experiment was carried throughout growth two seasons 2014 and 2015. Fruits were immersed in 0, 3, 6, and 9 mM ascorbic acid (AA) for 15 min at cold temperature. Thereafter, fruits were stored at cold temperature (6 ± 1 °C with 90% RH) for 27days. The results pointed out that the immersing banana fruits at 9 mM of AA were most effective in reducing chilling injury incidences in fruit peel. Also, the treatment reduced increases in cell membrane dysfunction at to lipid peroxidation (MDA) and protein oxidation (PCG) accumulation consequently, decreases ion leakage. Moreover, immersing in AA at 9 mM minimized superoxide anion (O2 −) and H2O2 production. Also, it increased significantly antioxidant enzyme activities during cold storage stress of ascorbate peroxidase (APX; CE: 1.11.1.11), peroxidase (POD; EC: 1.11.1.7), catalase (CAT; EC:1.11.1.6), and superoxide dismutase (SOD; EC: 1.15.1.1) so, less chilling injury symptoms on fruit peel which it reflects on fruit appearing compared to control fruit and other AA treatments. These results pointed out that the AA treatments at 9 mM might increase chilling tolerance of banana fruit by increasing antioxidant enzyme activities. Consequently, decrease/alleviate O2 − and H2O2 generation during cold storage stress. Thus, exogenous AA treatment at 9 mM could be a useful application to reduce/delay/alleviate CI in banana fruit during cold storage.

Regulatory effects of CaCl2, sodium isoascorbate, and 1‐methylcyclopropene on chilling injury of banana fruit at two ripening stages and the mechanisms involved

To improve fruit chilling tolerance during postharvest storage, banana fruit at two ripening stages (green and yellow) were pretreated with 2% (wt/vol) CaCl2 (Ca2+) or 1% (wt/vol) sodium isoascorbate (SI) under vacuum infiltration, or fumigated with 1.0 μL/L 1-methylcyclopropene (1-MCP), then stored at 6 °C. Application of Ca2+ or SI significantly reduced chilling injury index, electrolyte leakage, malondialdehyde content, and polyphenol oxidase activity of banana peel during storage at 6 °C. And Ca2+ or SI also sustained levels of firmness, peel lightness, and promoted activities of peroxidase, superoxide dismutase, catalase, and ascorbate peroxidase in banana at two ripening stages. Application of 1-MCP resulted in positive effects only on the visual quality of yellow ripening banana. Our results indicated that Ca2+ or SI could ameliorate chilling injury of both mature green and yellow ripening banana fruit stored at 6 °C; 1-MCP could enhance chilling tolerance of yellow ripening banana. Practical applications Refrigeration is a usual method for extending storage life of banana fruit. Like other tropical and subtropical fruits, banana is highly susceptible to chilling injury (CI) and develops CI symptoms of rapid peel browning, pulp rigidity, and pitting when stored at low temperature. Our results indicate that 2% (wt/vol) calcium chloride or 1% (wt/vol) sodium isoascorbate are effective methods in alleviating CI of the banana at two ripening stages. A total of 1.0 μL/L 1-methylcyclopropene significantly reduced CI of yellow ripening banana, while exacerbation of CI was observed in green maturity banana during the storage. This research not only provides environmentally friendly chemicals for postharvest application but also investigates the effects of chemical treatments on CI both of mature green banana and yellow ripening banana.

Banana fruit VQ motif-containing protein5 represses cold-responsive transcription factor MaWRKY26 involved in the regulation of JA biosynthetic genes.

Most harvested fruits and vegetables are stored at low temperature but many of them are highly sensitive to chilling injury. Jasmonic acid (JA), a plant hormone associated with various stress responses, is known to reduce chilling injury in fruits. However, little is known about the transcriptional regulation of JA biosynthesis in relation to cold response of fruits. Here, we show the involvement of a Group I WRKY transcription factor (TF) from banana fruit, MaWRKY26, in regulating JA biosynthesis. MaWRKY26 was found to be nuclear-localized with transcriptional activation property. MaWRKY26 was induced by cold stress or by methyl jasmonate (MeJA), which enhances cold tolerance in banana fruit. More importantly, MaWRKY26 transactivated JA biosynthetic genes MaLOX2, MaAOS3 and MaOPR3 via binding to their promoters. Further, MaWRKY26 physically interacted with a VQ motif-containing protein MaVQ5, and the interaction attenuated MaWRKY26-induced transactivation of JA biosynthetic genes. These results strongly suggest that MaVQ5 might act as a repressor of MaWRKY26 in activating JA biosynthesis. Taken together, our findings provide new insights into the transcriptional regulation of JA biosynthesis in response to cold stress and a better understanding of the molecular aspects of chilling injury in banana fruit.

Contribution of polyamines metabolism and GABA shunt to chilling tolerance induced by nitric oxide in cold-stored banana fruit

Effect of exogenous nitric oxide (NO) on polyamines (PAs) catabolism, γ-aminobutyric acid (GABA) shunt, proline accumulation and chilling injury of banana fruit under cold storage was investigated. Banana fruit treated with NO sustained lower chilling injury index than the control. Notably elevated nitric oxide synthetase activity and endogenous NO level were observed in NO-treated banana fruit. PAs contents in treated fruit were significantly higher than control fruit, due to the elevated activities of arginine decarboxylase and ornithine decarboxylase. NO treatment increased the activities of diamine oxidase, polyamine oxidase and glutamate decarboxylase, while reduced GABA transaminase activity to lower levels compared with control fruit, which resulted the accumulation of GABA. Besides, NO treatment upregulated proline content and significantly enhanced the ornithine aminotransferase activity. These results indicated that the chilling tolerance induced by NO treatment might be ascribed to the enhanced catabolism of PAs, GABA and proline.

Hydrogen sulfide alleviates chilling injury of banana fruit by enhanced antioxidant system and proline content

Hydrogen sulfide (H2S) has been proven to act as an antioxidant in prolonging storage of postharvest fruits and vegetables, indicating that H2S might have the potential to ameliorate chilling injury (CI). Effect of H2S fumigation released from 0.5mM H2S donor (NaHS) on banana fruit during chilling storage followed by a ripening period was evaluated. Results demonstrated that H2S fumigation maintained higher values of lightness, peel firmness and reduced accumulation of malondialdehyde. It was also found that H2S promoted the phenylalanine ammonia lyase activity, total phenolics content and antioxidant capacity. Moreover, H2O2 and superoxide anion accumulation were reduced by H2S with up-regulated activities of guaiacol peroxidase, superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase. Further investigation on proline metabolism showed that elevated proline content which resulted from increased Δ1-pyrroline-5-carboxylate synthetase activity and decreased proline dehydrogenase activity, might be related to CI tolerance improvement. These data indicate that H2S alleviates CI of banana fruit may through the enhancement of antioxidant system and proline content.