Revealing Further Insights on Chilling Injury of Postharvest Bananas by Untargeted Lipidomics

Alteration of surface morphologies and chemical composition of cuticle in response to chilling injury in papaya (Carica papaya L.) after harvest

The alteration of surface microstructures and chemical composition in cuticle of papaya fruit in response to chilling stress were comparatively studied between cultivars of 'Risheng' and 'Suihuang' after harvest. Fruit surface was covered by fissured wax layers in both cultivars. The presence of granule crystalloids was cultivar dependent, with higher abundance in 'Risheng' and lower in 'Suihuang'. Various typical very-long-chain aliphatics i.e., fatty acids, aldehydes, n-alkanes, primary alcohols, and n-alkenes dominated waxes; and cutin monomers were prominently 9/10,16-dihydroxyhexadecanoic acid in papaya fruit cuticle. Chilling pitting symptom was accompanied by modification of granule crystalloids into flat appearance and decreased primary alcohols, fatty acids, and aldehydes in 'Risheng', but no evident changes in 'Suihuang'. The response of cuticle to chilling injury in papaya fruit might be not directly related to the overall amount of waxes and cutin monomers, but more likely to the alteration of appearance morphologies and chemical composition in cuticle.

Review of recent advances in post-harvest techniques for tropical cut flowers and future prospects: Heliconia as a case-study

Aesthetic attributes and easy-to-grow nature of tropical cut flowers (TCFs) have contributedto their potential for increased production. The dearth of information regarding agronomic practices and lack of planting materials are the key hindrances against their fast expansion. Unconventional high-temperature storage requirements and the anatomy of the peduncle contribute topoor vase life performance, while troublesome packaging and transport due to unusual size and structureprimarily cause post-harvest quality deterioration. Nonetheless, the exotic floral structuresconsequently increase market demand, particularly in temperate countries. This boosts studies aimed at overcoming post-harvest hindrances. While a few TCFs (Anthurium, Strelitzia, Alpinia, and a few orchids) are under the spotlight, many others remain behind the veil. Heliconia, an emerging specialty TCF (False Bird-of-Paradise, family Heliconiaceae), is one of them. The structural uniquenessand dazzling hues of Heliconia genotypes facilitate shifting its position from the back to the forefrontof the world floriculture trade. The unsatisfactory state-of-the-art of Heliconia research and the absence of any review exclusively on it are the key impetus for structuring this review. In addition to the aforementioned setbacks, impaired water uptake capacity after harvest, high chilling sensitivity, and the proneness of xylem ducts to microbial occlusion may be counted as a few additional factors that hinder its commercialization. This review demonstrates the state-of-the-art of post-harvest research while also conceptualizing the implementation of advanced biotechnological aid to alleviate the challenges, primarily focusing on Heliconia (the model crop here) along with some relevant literature on its other allied members. Standard harvesting indices, grading, and packaging are also part of the entire post-harvest operational chain, but since these phases are barely considered in Heliconia and the majority of tropical ornamentals except a few, a comprehensive account of these aspects has also been given. The hypothesized cues to nip chilling injury, resorting to different bio-chemical treatments, nano-based technology, and advanced packaging techniques, may help overcome preservation difficulties and propel its transition from niche to the commercial flower market. In a nutshell, readers will gain a comprehensive overview of how optimum post-harvest handling practices can rewardingly characterize this unique group of TCFs as the most remunerative component.

Azadirachtin exposure inhibit ovary development of Spodoptera litura (Lepidoptera: Noctuidae) by altering lipids metabolism event and inhibiting insulin signaling pathways

Lipids are main energy source for insects reproduction, which are becoming emerging target for pest management. Azadirachtin (AZA) is a multi-targeted and promising botanical insecticide, but its reproduction toxicity mechanism related to lipids metabolism is poorly understood. Here, we applied lipidomic and transcriptomic to provide a comprehensive resource for describing the effect of AZA on lipids remodeling in ovary of Spodoptera litura. The results showed that AZA exposure obviously altered the contents of 130 lipids subclasses (76 upregulated and 54 downregulated). In detail, AZA exposure changed the length and saturation degrees of fatty acyl chain of most glycerolipid, phospholipid and sphingolipid as well as the expression of genes related to biosynthesis of unsaturated fatty acids and fatty acids elongation. Besides, following the abnormal lipids metabolism, western blot analysis suggested that AZA induce insulin resistance-like phenotypes by inhibiting insulin receptor substrates (IRS) /PI3K/AKT pathway, which might be responsible for the ovary abnormalities of S. litura. Collectively, our study provided insights into the lipids metabolism event in S. litura underlying AZA exposure, these key metabolites and genes identified in this study would also provide important reference for pest control in future.

Reduction of Membrane Lipid Metabolism in Postharvest Hami Melon Fruits by n-Butanol to Mitigate Chilling Injury and the Cloning of Phospholipase D-β Gene

To investigate the effect of n-butanol on postharvest membrane lipid metabolism of Hami melon (Cucumis melo 'Hami'), the fruits were soaked in a 1.0% solution of n-butanol for 30 min with water as the control. Symptoms of chilling injury were observed regularly, and the indices related to permeability and membrane lipid metabolism of pericarp cells were measured. The results showed that treatment with n-butanol inhibited the increase in chilling injury index, membrane permeability, and malondialdehyde content of Hami melon fruits, promoted an increase in the contents of phosphatidyl alcohol and unsaturated fatty acids, such as linoleic acid, linolenic acid, oleic acid (except 14 d), and erucic acid (28-42 d), and decreased the content of saturated fatty acids, stearic acid (0-28 d), phosphatidic acid (except for 21 d), and the key enzymes of membrane lipid metabolism compared with the control. The activities of phospholipase D (PLD) and lipoxygenase (LOX) and the downregulation of the levels of expression CmPLD-β and CmLOX (42 d only) genes reduced the chilling injury index of Hami melon and alleviated the further expansion of chilling injury symptoms in the fruits. We also cloned the key gene of membrane lipid metabolism CmPLD-β, which was obtained by pre-transcriptome screening of the pericarp. We found that CmPLD-β of Hami melon had the closest affinity with cucumber (CsXP5), indicating that the CmPLD-β gene of Hami melon was functionally similar to that of cucumber. In addition, a two-fold alignment analysis of CmPLD-β and CmXP5 base sequences indicated that the base sequences of the two promoter regions differed from each other.

Lipidomic and transcriptomic profiles of glycerophospholipid metabolism during Hemerocallis citrina Baroni flowering

BACKGROUND

Hemerocallis citrina Baroni (daylily) is a horticultural ornamental plant and vegetable with various applications as a raw material in traditional Chinese medicine and as a flavouring agent. Daylily contains many functional substances and is rich in lecithin, which is mostly composed of glycerophospholipids. To study the comprehensive dynamic changes in glycerophospholipid during daylily flowering and the underlying signalling mechanisms, we performed comprehensive, time-resolved lipidomic and transcriptomic analyses of 'Datong Huanghua 6' daylily.

RESULTS

Labelling with PKH67 fluorescent antibodies clearly and effectively helped visualise lipid changes in daylily, while relative conductivity and malonaldehyde content detection revealed that the early stages of flowering were controllable processes; however, differences became non-significant after 18 h, indicating cellular damage. In addition, phospholipase D (PLD) and lipoxygenase (LOX) activities increased throughout the flowering process, suggesting that lipid hydrolysis and oxidation had intensified. Lipidomics identified 558 lipids that changed during flowering, with the most different lipids found 12 h before and 12 h after flowering. Transcriptome analysis identified 13 key functional genes and enzymes in the glycerophospholipid metabolic pathway. The two-way orthogonal partial least squares analysis showed that diacylglycerol diphosphate phosphatase correlated strongly and positively with phosphatidic acid (PA)(22:0/18:2), PA(34:2), PA(34:4), and diacylglycerol(18:2/21:0) but negatively with phospholipase C. In addition, ethanolamine phosphotransferase gene and phospholipid-N-methyltransferase gene correlated positively with phosphatidylethanolamine (PE)(16:0/18:2), PE(16:0/18:3), PE(33:2), and lysophosphatidylcholine (16:0) but negatively with PE(34:1).

CONCLUSIONS

Overall, this study elucidated changes in the glycerophospholipid metabolism pathway during the daylily flowering process, as well as characteristic genes, thus providing a basis for future studies of glycerophospholipids and signal transduction in daylilies.

Amelioration of Chilling Injury by Fucoidan in Cold-Stored Cucumber via Membrane Lipid Metabolism Regulation

Cucumber fruit is very sensitive to chilling injury, which rapidly depreciates their commodity value. Herein, the effect of fucoidan treatment on cucumber under cold stress were investigated. Fucoidan treatment of cold-stored cucumber alleviated the occurrence of chilling injury, delayed weight loss, lowered electrolyte leakage and respiration rate, and retarded malondialdehyde accumulation. Different from the control fruit, fucoidan treated fruit showed a high level of fatty acid unsaturated content, fatty acid unsaturation, and unsaturation index and increased ω-FDAS activity, along with upregulated expression levels of CsSAD and CsFAD genes. Fucoidan reduced the phosphatidic acid content and membrane lipid peroxidation, lowered the phospholipase D (PLD) and lipoxygenase (LOX) activity, and downregulated the expression levels of CsPLD and CsLOX genes. Collectively, fucoidan treatment maintained the integrity of cell membrane in cold-stress cucumbers. The results provide a new prospect for the development of fucoidan as a preservative agent in the low-temperature postharvest storage of cucumbers.

Dissecting postharvest chilling injury through biotechnology

Paradoxically, refrigerating many fruits and vegetables destroys their quality, and may even accelerate their spoilage. This phenomenon, known as postharvest chilling injury (PCI), affects produce from tropical and subtropical regions and leads to economic and postharvest loss and waste. Low temperatures are used to pause the physiological processes associated with senescence, but upon rewarming, these processes may resume at an accelerated rate. Chilling-injured produce may be discarded for not meeting consumer expectations or may prematurely deteriorate. In this review, we describe progress made in identifying the cellular and molecular processes underlying PCI, and point to advances in biotechnological approaches for ameliorating symptoms. Further, we identify the gaps in knowledge that must be bridged to develop effective solutions to PCI.

Prediction of banana quality during storage by brown area

To study the feasibility of evaluating the quality characteristics of banana based on the browning area. The texture characteristics, total soluble solids (TSS), ascorbic acid, malondialdehyde (MDA) concentrations, relative conductivity, polyphenol oxidase, peroxidase, and phenylalanine ammonia-lyase (PAL) activities in banana peels were detected during storage. A linear model was made by principal component analysis and multiple linear regression between the banana browning area and characteristic indices. The results showed that the changes in the physiological characteristics of bananas were significantly different during different storage periods. The main factors that affected the banana browning area were relative conductivity, PAL, TSS, and MDA, indicating that lipid peroxidation, respiration, and metabolism of phenylpropanoids had significant influence on the banana browning area during storage. Thus, it is feasible to predict banana quality based on changes in browning area, which could be a rapid and non-destructive detection of banana quality during storage.

Advances in chilling injury of postharvest fruit and vegetable: Extracellular ATP aspects

Due to the global use of cold chain, the development of postharvest technology to reduce chilling injury (CI) in postharvest fruits and vegetables during storage and transport is needed urgently. Considerable evidence shows that maintaining intracellular adenosine triphosphate (iATP) in harvested fruits and vegetables is beneficial to inhibiting CI occurrence. Extracellular ATP (eATP) is a damage-associated signal molecule and plays an important role in CI of postharvest fruits and vegetables through its receptor and subsequent signal transduction under low-temperature stress. The development of new aptasensors for the simultaneous determination of eATP level allows for better understanding of the roles of eATP in a myriad of responses mediated by low-temperature stress in relation to the chilling tolerance of postharvest fruits and vegetables. The multiple biological functions of eATP and its receptors in postharvest fruits and vegetables were attributed to interactions with reactive oxygen species (ROS) and nitric oxide (NO) in coordination with phytohormones and other signaling molecules via downstream physiological activities. The complicated interconnection among eATP in relation to its receptors, eATP/iATP homeostasis, ROS, NO, and heat shock proteins triggered by eATP recognition has been emphasized. This paper reviews recent advances in the beneficial effects of energy handling, outlines the production and homeostasis of eATP, discusses the possible mechanism of eATP and its receptors in chilling tolerance, and provides future research directions for CI in postharvest fruits and vegetables during low-temperature storage.

Effect of Drought Stress on Degradation and Remodeling of Membrane Lipids in Nostoc flagelliforme

Nostoc flagelliforme is a kind of terrestrial edible cyanobacteria with important ecological and economic value which has developed special mechanisms to adapt to drought conditions. However, the specific mechanism of lipidome changes in drought tolerance of N. flagelliforme has not been well understood. In this study, the ultra-high-performance liquid chromatography and mass spectrometry were employed to analyze the lipidome changes of N. flagelliforme under dehydration. A total of 853 lipid molecules were identified, of which 171 were significantly different from that of the control group. The digalactosyldiacylglycerol/monogalactosyldiacylglycerol (DGDG/MGDG) ratio was increased. The amount of wax ester (WE) was sharply decreased during drought stress, while Co (Q10) was accumulated. The levels of odd chain fatty acids (OCFAs) were increased under dehydration, positively responding to drought stress according to the energy metabolism state. In conclusion, the lipidomic data corroborated that oxidation, degradation, and biosynthesis of membrane lipids took place during lipid metabolism, which can respond to drought stress through the transformation of energy and substances. Besides, we constructed a lipid metabolic model demonstrating the regulatory mechanism of drought stress in N. flagelliforme. The present study provides insight into the defense strategies of cyanobacteria in lipid metabolic pathways.

Reversible changes in galactolipid saturation level and head group composition are associated with tolerance to postharvest chilling in tomato fruit

BACKGROUND

Chilling injury (CI) is a physiological disorder that results in a limitation for cold storage (CS) of many fruits and vegetables. The low temperature-induced changes in the properties and composition of cell membranes are involved in the response to chilling temperature and in the mechanism of CI and tolerance.

RESULTS

We compared the changes in the lipid composition by gas chromatography-mass spectrometry before, immediately after CS, as well as during a 3-day subsequent period, of tomato fruits with different chilling-sensitivity: Micro-Tom (tolerant) and Minitomato (susceptible). The changes in linolenic acid content, double bond index and digalactosyldiacylglycerol/monogalactosyldiacylglycerol ratio (DGDG/MGDG) showed membrane fluidity adjustment, depending on the temperature. By a database search, we identified 18 membrane-bound fatty acid desaturase (FAD) genes and five DGDG synthases (DGD) genes that phylogenetically clustered into four and two subfamilies, respectively. The FAD and DGD genes were differentially expressed in response to CS, as determined by quantitative reverse transcriptase-polymerase chain reaction analysis.

CONCLUSION

The data strongly suggest that reversion of CS-induced changes during the recovery period is important for the proper function of the membrane and tolerance to postharvest CI in tomato fruit. © 2021 Society of Chemical Industry.

NAC-mediated membrane lipid remodeling negatively regulates fruit cold tolerance

Low temperatures are known to destroy cell membranes' structural integrity by affecting the remodeling of their phospholipids. Fruits stored at low temperature are prone to chilling injury, characterized by discoloration, absence of ripening, surface pitting, growth inhibition, flavor loss, decay, and wilting. Phosphatidic acid, a vital second-messenger lipid in plants, is known to accumulate in response to different kinds of stress stimuli. However, the regulatory mechanism of its production from the degradation of phospholipids remains poorly understood. We identified two cold-responsive NAC (NAM/ATAF1/CUC2) transcription factors from bananas, namely, MaNAC25 and MaNAC28, which negatively regulated cold tolerance in banana fruits by upregulating the expression of phospholipid degradation genes in banana fruits. Furthermore, MaNAC25 and MaNAC28 formed a positive feedback loop to induce phospholipid degradation and produce phosphatidic acid. In contrast, ethylene directly inhibited the degradation of phospholipids in banana and transgenic tomato fruits. In addition, ethylene reduced the activity of MaNAC25 and MaNAC28, thereby inhibiting phospholipid degradation. To conclude, NAC-mediated membrane lipid remodeling negatively regulates the cold tolerance of banana and transgenic tomato fruits.

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.

The state of the art in plant lipidomics

Lipids are a group of compounds with diverse structures that perform several important functions in plants. To unravel and better understand their in vivo functions, plant biologists have been using various lipidomic technologies including liquid-chromatography (LC)-mass spectrometry (MS). However, there are still significant challenges in LC-MS based plant lipidomics, which need to be addressed. In this review, we provide an overview of the key developments in LC-MS based lipidomic approaches to detect and identify plant lipids with emphasis on areas that can be further improved. Given that the cellular lipidome is estimated to contain hundreds of thousands of lipids,^1,2 many of the lipid structures remain to be discovered. Furthermore, the plant lipidome is considered to be significantly more complex compared to that of mammals. Recent technical developments in mass spectrometry have made the detection of novel lipids possible; hence, approaches that can be used for plant lipid discovery are also discussed.

An Arabidopsis lipid map reveals differences between tissues and dynamic changes throughout development

Mass spectrometry is the predominant analytical tool used in the field of plant lipidomics. However, there are many challenges associated with the mass spectrometric detection and identification of lipids because of the highly complex nature of plant lipids. Studies into lipid biosynthetic pathways, gene functions in lipid metabolism, lipid changes during plant growth and development, and the holistic examination of the role of plant lipids in environmental stress responses are often hindered. Here, we leveraged a robust pipeline that we previously established to extract and analyze lipid profiles of different tissues and developmental stages from the model plant Arabidopsis thaliana. We analyzed seven tissues at several different developmental stages and identified more than 200 lipids from each tissue analyzed. The data were used to create a web-accessible in silico lipid map that has been integrated into an electronic Fluorescent Pictograph (eFP) browser. This in silico library of Arabidopsis lipids allows the visualization and exploration of the distribution and changes of lipid levels across selected developmental stages. Furthermore, it provides information on the characteristic fragments of lipids and adducts observed in the mass spectrometer and their retention times, which can be used for lipid identification. The Arabidopsis tissue lipid map can be accessed at http://bar.utoronto.ca/efp_arabidopsis_lipid/cgi-bin/efpWeb.cgi.

The Involvement of Energy Metabolism and Lipid Peroxidation in Lignin Accumulation of Postharvest Pumelos

Lignification is especially prominent in postharvest pumelo fruit, which greatly impairs their attractiveness and commercial value. This study investigated the energy metabolism and lipid peroxidation and their relationship with accumulated lignin content in juice sacs of “Hongroumiyou” (HR) during 90 d of storage at 25 °C. The results indicated that, the alterations of energy metabolism in juice of sacs of postharvest pumelos was featured by a continuous decline in energy charge and ATP/ADP; an increase in succinic dehydrogenase (SDH) activity before 30 d and increases in activities of cytochrome c oxidase (CCO) and F₀F₁-ATPase before 60 d; but declines in activities of Ca²⁺-ATPase and H⁺-ATPase. Additionally, enhanced contents of H₂O₂, O₂⁻, and –OH scavenging rate; increased malondialdehyde (MDA) content; and transformation of unsaturated fatty acids (USFA) to saturated fatty acids (USFA) and reduced USFA/SFA (U/S) could result in lipid peroxidation and membrane integrity loss. Moreover, correlation analysis showed that lignin accumulation was in close relation to energy metabolism and lipid peroxidation in juice sacs of postharvest pumelos. These results gave evident credence for the involvement of energy metabolism and lipid peroxidation in the lignin accumulation of HR pumelo fruit during postharvest storage.