Delayed Fruit Softening Research Articles

Postharvest melatonin application attenuates browning, delays softening, and maintains the antioxidant potential of jackfruit bulbs

Although the impact of postharvest melatonin (MLT) application in extending the storage life of horticultural produce has been widely studied, its effect in jackfruit remains unknown. This investigation evaluates the influence of MLT dip application (0, 0.05, 0.1, and 0.2 mM) on browning, softening and oxidative stress in cold-stored jackfruit bulbs over a period of 20d. All MLT treatments reduced browning index and oxidative stress, while activities of browning-related enzymes were comparatively lower in the 0.1 mM MLT treatment. Treatment with 0.2 mM MLT maintained elevated levels of antioxidants as compared to control. Higher bulb firmness, total pectin and cellulose content with considerably lower activities of cell wall degrading enzymes were observed in all MLT treatments. In conclusion, MLT (0.1 and 0.2 mM) is an effective treatment for mitigating postharvest browning and oxidative stress in addition to delaying fruit softening and maintaining the antioxidant potential of cold-stored jackfruit bulbs.

Advancing Fruit Preservation: Ecofriendly Treatments for Controlling Fruit Softening

Textural softening is a major factor that limits the storage potential of fruit. Fresh produce markets incur severe financial losses due to excessive fruit softening. The application of preservation strategies aimed at mitigating fruit softening is crucial for optimising the marketability of fruit. Proposed preservation strategies include ecofriendly treatments, namely, hexanal, edible coatings, heat treatments, ozone and UV-C irradiation. These treatments optimise firmness retention by targeting the factors that affect fruit softening, such as ethylene, respiration rates, enzymes and pathogens. This review discusses the mechanisms by which ecofriendly treatments inhibit fruit softening, providing insights into their effect on ethylene biosynthesis, cell wall metabolism and disease resistance. Although ecofriendly treatments offer a promising and sustainable approach for delaying fruit softening, the optimisation of treatment application protocols is needed to improve their efficacy in retaining fruit firmness. Studies reporting on the molecular mechanisms by which ecofriendly treatments inhibit fruit softening are limited. Future studies should prioritise proteomic and transcriptome analyses to advance our understanding of the underlying molecular mechanisms by which ecofriendly treatments delay the fruit-softening process.

Melatonin extends shelf life in postharvest okra via delaying fruit softening and reducing weight loss.

Melatonin, a hormone present in animals and some plants, has garnered attention for its potential in preserving harvested produce. Softening due to changes in cell wall composition and wilting caused by weight loss are the major reasons for the loss of commercial value in postharvest okra. This study aimed to evaluate the impact of melatonin on the softening and weight loss of postharvest okra. The results revealed that the application of melatonin had a significant influence on the maintenance of fruit firmness by inhibiting the breakdown and dissolution of cell wall polysaccharides by suppressing the expression of specific genes responsible for cell wall degradation in okra. Conversely, melatonin treatment positively influenced the expression of genes involved in the synthesis of cell wall components. Furthermore, the treatment exhibited notable benefits in reducing weight loss in okra, which was accomplished by promoting the closure of stomata - the tiny pores on the surface of the fruit. Melatonin could serve as a novel approach to reduce water loss, delay fruit softening and extend the shelf life of okra. © 2024 Society of Chemical Industry.

γ-Aminobutyric acid delays fruit softening in postharvest kiwifruit by inhibiting starch and cell wall degradation

The effects of 10 mM γ-aminobutyric acid (GABA) treatment on fruit softening, starch degradation, cell wall disassembly in cold-stored ‘Hongyang’ kiwifruit after harvest were investigated. The results depicted that GABA treatment maintained firmness and delayed fruit softening during storage by retaining high starch content due to the inhibition of the transcription levels of related starch-degrading genes, such as AcGWD, AcPWD, and AcBAMs. In addition, compared with the control, higher level of chelated-soluble pectin, Na2CO3-soluble pectin, hemicellulose and cellulose content but lower water-soluble pectin content were observed in the treated kiwifruit as GABA suppressed cell wall breakdown by down-regulating the expression of AcPE, AcPG, AcBGALs, and AcXTHs. In summary, our results indicated that exogenous GABA contributes to maintaining fruit firmness, delaying softening in postharvest kiwifruit by inhibiting starch degradation and preserving cell wall metabolism.

Effect of ozone treatment on the decay and cell wall metabolism during the postharvest storage of cantaloupe

Cantaloupe is a popular summer fruit with immense market potential in China. However, the cantaloupe fruits generally soften rapidly after harvest, which dramatically reduces their economic value. The ozone treatment has been found to be effective in delaying the softening of cantaloupe fruit. The results indicated that ozone treatment significantly inhibited the mycelial growth of Fusarium hypha. The ozone treatment was able to delay the decline of total soluble solids, lower the respiration rate, and maintain the fruit's firmness without damaging fruit quality. The study also indicated that the activity and gene expression of cell wall degrading enzymes such as polygalacturonase (PG), pectin methylesterase (PME), β-galactosidase (β-gal), cellulose (Cx), and α-l-arabinofuranosidase (α-l-Af), were inhibited under ozone treatment, which also suppressed the degradation of cell wall components associated with fruit softening (protopectin, soluble pectin, cellulose, and hemicellulose). These changes may contribute to the maintenance of cell wall components, thereby delaying the fruit softening. In conclusion, these results suggested that ozone can improve the fruit quality of cantaloupe by suppressing postharvest fungal diseases and delaying fruit softening, which provides a theoretical basis for further research on cell wall metabolism during cantaloupe storage.

Application of 1-MCP does not slow down the ripening process of Mango (Mangifera indica L)

Fruits and vegetables are perishable so that they are easily degraded and thus have a short shelf life. Some studies have been carried out intensively to extend the shelf life of fruit with the application of 1-methylcyclopropene (1-MCP) which is an ethylene inhibitor (indirectly) to slow down the ripening process and extend its shelf life. The benefits of using 1-MCP to delay fruit softening have also been published, however the inhibition of ripening and fruit softening by 1-MCP in mango (Mangifera indica) is very limited. 1-MCP delays fruit softening during storage by indirectly inhibiting ethylene synthesis and slowing the activity of cell wall-damaging enzymes, such as pectin methyl esterase (PME). To study the effect of 1-MCP on mango fruit quality and its shelf life, the experiment was carried out by measuring weight loss, colour, firmness, vitamin C, total soluble solids, titratable acidity, and reducing sugars periodically. For all fruit samples, the pulp was chopped, frozen in liquid nitrogen, and then stored at 8°C until further use. The results showed that application of 1-MCP at room temperature did not slow down neither the senescence process nor the shelf life of mango fruit on weight loss, colour, firmness, vitamin C, total soluble solids, titratable acidity, and reducing sugars parameters.

Morin Treatment Delays the Ripening and Senescence of Postharvest Mango Fruits.

A 0.005% and 0.01% morin treatment was applied to treat mango fruits stored under ambient conditions (25 ± 1 °C) with 85-90% relative humidity, and the effects on quality indexes, enzyme activity related to antioxidation and cell wall degradation, and gene expressions involved in ripening and senescence were explored. The results indicate that a 0.01% morin application effectively delayed fruit softening and yellowing and sustained the nutritional quality. After 12 days of storage, the contents of soluble sugar and carotenoid in the treatment groups were 68.54 mg/g and 11.20 mg/100 g, respectively, lower than those in control, while the vitamin C content in the treatment groups was 0.58 mg/g, higher than that in control. Moreover, a morin application successively enhanced the activity of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), but reduced the activity of polygalacturonase (PG) and pectin lyase (PL). Finally, real-time PCR and correlation analysis suggested that morin downregulated the ethylene biosynthesis (ACS and, ACO) and signal transduction (ETR1, ERS1, EIN2, and ERF1) genes, which is positively associated with softening enzymes (LOX, EXP, βGal, and EG), carotenoid synthesis enzymes (PSY and, LCYB), sucrose phosphate synthase (SPS), and uncoupling protein (UCP) gene expressions. Therefore, a 0.01% morin treatment might efficiently retard mango fruit ripening and senescence to sustain external and nutritional quality through ethylene-related pathways, which indicates its preservation application.

Integrated analysis of postharvest storage characteristics of seven apple cultivars and transcriptome data identifies MdBBX25 as a negative regulator of fruit softening during storage in apples

Apple is classified as a climacteric fruit, characterized by a rapid surge in ethylene levels at the onset of ripening. However, there is significant variation in the degree and timing of ripening and softening among different apple cultivars. Understanding the molecular mechanisms underlying fruit softening and the associated changes in cell wall integrity is crucial for improving fruit quality and extending shelf life. In this study, we conducted a comparative analysis of fruit firmness and ethylene production among seven apple cultivars with different softening patterns during storage. We also examined the expression patterns of genes and enzyme activities involved in cell wall metabolism. Our results showed that fruit firmness was negatively correlated with ethylene production rate, respiration rate, soluble pectin content, cellulase activity, polygalacturonase activity, and β-glucosidase activity, while it was positively correlated with protopectin content and cellulose content. Furthermore, we identified a BBX transcription factor gene, MdBBX25, that was negatively correlated with fruit softening during storage. Overexpression of MdBBX25 resulted in delayed fruit softening by suppressing ethylene biosynthesis and cell wall-related genes, whereas silencing of MdBBX25 accelerated fruit softening by promoting ethylene biosynthesis and cell wall-related genes in apple. Our findings provide insights into the role of MdBBX25 as a negative regulator of fruit softening through the modulation of ethylene biosynthesis and cell wall degradation during storage.

Aminoethoxyvinylglycine Reduces Preharvest Fruit Drop and Fruit Ethylene Evolution in ‘Red Delicious’ Apple but Affects Fruit Size and Quality Inconsistently

Aminoethoxyvinylglycine (AVG) is widely used in commercial apple (Malus ×domestica Borkh.) production to reduce preharvest fruit drop (PFD) and delay ripening for harvest management. Recently, the maximum allowable concentration of AVG was doubled (up to 264 mg⋅L−1). Reports of the relationship between the AVG concentration and fruit growth, size, and quality have been contradictory. We evaluated the relationship between the AVG concentration and PFD, fruit size, fruit quality, and expression of ethylene signaling-related and cell wall modification-related genes. Experiments were conducted in 2019 and 2020 using mature ‘Red Delicious’ in western North Carolina. The AVG treatments [0 and 132 (AVG-1x) and 264 mg⋅L−1 (AVG-2x)] were applied 3 weeks before the expected harvest. The AVG treatments reduced fruit drop and internal ethylene concentration relative to the control in both years. There was no difference in drop between AVG-1x and AVG-2x applications. Only in 2020 did AVG treatments delay fruit softening and starch hydrolysis and reduce soluble solids concentration. There were no effects on red fruit color development. Fruit size was unaffected by AVG in 2019, but it was reduced in 2020 with the AVG-2x application. AVG reduced ethylene synthesis and altered signaling, evidenced by decreased relative expression of genes related to ethylene signaling (ARGOS1, ARGOS2). AVG applications also reduced the expression of EXPA8;1, suggesting that reduced cell wall disassembly was associated with a reduction in fruit softening. These results indicate that preharvest applications of 132 mg⋅L−1 AVG effectively reduced PFD via altering ethylene evolution and signaling. Use of a higher AVG concentration was of limited benefit.

Melatonin treatment inhibits mango fruit (Cv. ‘Guiqi’) softening by maintaining cell wall and reactive oxygen metabolisms during cold storage

Mango fruit (Mangifera indica L, cv. ‘Guiqi’) was treated with melatonin (1 mM) to explore the changing mechanisms in fruit softening and to examine the effects of melatonin on the interaction between the cell wall and reactive oxygen metabolisms subjected to cold storage. The results depicted that compared to control, melatonin treatment (1) improved storage life by maintaining the higher ascorbic acid (AsA) and reduced glutathione (GSH) contents, as well as maintained higher insoluble pectin, hemicellulose, and cellulose contents, and lower soluble pectin content of ‘Guiqi’ mango fruit. (2) Delayed fruit softening by maintaining higher firmness and suppressing the activities of polygalacturonase (PG), pectin methyl esterase (PME), cellulase (Cx), and β-glucosidase (β-glu); and cell wall degrading genes (MiPG14, MiPME, MiCel, and Miβ-glu). (3) Enhanced storage quality by inhibiting decay incidence, respiration rate, and weight loss rate; increased activity of glutathione reductase (GR) and inhibits reactive oxygen species (ROS) metabolites at cold storage. These results indicate that exogenous melatonin could delay mango fruit softening by maintaining cell wall metabolism, inhibiting ROS metabolites (O2.- and H2O2) accumulation via enhancement of non-enzymatic (AsA and GSH contents) and enzymatic (GR activity) antioxidants, and thus maintaining quality and improved storage life.

Organic Aminoethoxyvinylglycine Is an Effective Alternative for Reducing Apple Preharvest Drop

Organic apple (Malus ×domestica Borkh.) growers lack effective strategies to manage preharvest drop. For susceptible cultivars, yield losses caused by preharvest drop can exceed 30% at the beginning of harvest. To address this issue, a formulation of aminoethoxyvinylglyine (AVG) designed for organic use was developed and compared with a commercially available AVG formulation. We evaluated the effects and interactions of the AVG formulation and application number on preharvest drop and fruit maturity in 2017 and 2018. We selected 30 pairs of mature ‘Oregon Spur II Red Delicious’/‘M. 111’ trees planted at the Mountain Horticultural Crops Research and Extension Center in Mills River, NC, USA. Trees were planted with spacing of 2.7 × 6.1 m, trained to a central leader, and received plant protectant sprays that adhered to local recommendations throughout the growing season. Both AVG formulations were applied at 132 mg⋅L−1 at 3 or 3 + 1 weeks before the anticipated harvest. An untreated control was also included for comparison. The experiment had six replicates and a randomized complete block design with a 2 × 2 augmented factorial treatment structure. A one-way analysis of variance was performed and single degree of freedom contrasts were used to compare treatment groups of interest. During both years, organic and conventional AVG were equally effective for reducing preharvest drop and delaying fruit softening and starch hydrolysis at harvest. During one year, increasing the number of applications of AVG reduced cumulative fruit drop, delayed fruit softening at harvest, and reduced internal ethylene concentrations. Inconsistencies in responses across years may be explained, in part, by abnormally warm temperatures observed in 2018. AVG approved for organic use appears to be a promising preharvest drop management technology with efficacy similar to that of conventional AVG.

Fine mapping and gene silencing pinpoint Capana10g002229 as a strong candidate gene regulating the deciduous character of ripe pepper fruit (Capsicum spp.).

The pepper S locus, which controls the deciduous character of ripe fruit, was first fine mapped into an interval with a physical length of ~ 38.03kb on chromosome P10. Capana10g002229, encoding a polygalacturonase, was proposed as a strong candidate gene based on sequence comparison, expression pattern analysis and virus-induced gene silencing (VIGS). The deciduous character of ripe fruit, which is controlled by the dominant S locus, is a domesticated trait with potential value in the pepper processing industry (Capsicum spp.). However, the gene associated with the S locus has not been identified. Here, one major QTL designated S10.1 was detected by using the F2 population (n = 155) derived from BA3 (Capsicum annuum) × YNXML (Capsicum frutescens) and was further verified in an intraspecific backcross population (n = 254) derived from the cross between BB3 (C. annuum) and its wild relative Chiltepin (C. annuum var. glabriusculum) with BB3 as the recurrent parent. Then, a large BC1F2 population derived from the self-pollination of BB3 × (BB3 × Chiltepin) individuals and comprising 4217 individuals was used to screen the recombinants, and the S locus was ultimately delimited into a 38.03-kb region on chromosome P10 harbouring four annotated genes. Capana10g002229, encoding a polygalacturonase (PG), was proposed as the best candidate gene for S based on sequence comparison and expression pattern analyses. Downregulation of Capana10g002229 in fruits through VIGS significantly delayed fruit softening and abscission from the fruit-receptacle junction. Taken together, the results show that Capana10g002229 could be regarded as a strong candidate gene associated with the S locus in pepper. These findings not only lay a foundation for deciphering the molecular mechanisms underlying pepper domestication but also provide a strategy for genetic improvement of the deciduous character of ripe fruit using a marker-assisted selection approach.

Tannic acid exerts antifungal activity in vitro and in vivo against Alternaria alternata causing postharvest rot on apple fruit

Alternaria alternata is one of the main pathogens that causes black spot rot of apple fruit, mainly postharvest. Also, A. alternata can attack many other fruits and vegetables in most of the world's natural environments. In this study, the antifungal efficacy of tannic acid (TA) against A. alternata and its potential mechanisms were investigated. An in vitro bioassay suggested that 5.0 mg mL−1 TA significantly inhibited the mycelial growth and spore germination of A. alternata. The enzyme activities of hexokinase, phosphofructokinase and pyruvate kinase in glycolytic metabolism were decreased in A. alternata treated with TA. The accumulation of glucose content and the reduction of pyruvate content in A. alternata further confirmed that TA may block the glycolytic metabolism of this fungus, resulting in insufficient energy supply for cells. In addition, TA immersion treatment significantly reduced the development of lesion areas on apple fruits caused by A. alternata and delayed fruit softening during the storage period. The application of TA also increased the activity of chitinase, β-1,3-glucanase and phenylalanine ammonialyase and the contents of total phenolic compounds and flavonoids in apple fruit, indicating the activation of defense-related enzymes and phenylpropane metabolites. TA could potentially be used to prevent and control postharvest Alternaria rot by exerting antifungal activity on A. alternata and inducing resistance in apple fruit.

Proanthocyanidins Delay Fruit Coloring and Softening by Repressing Related Gene Expression during Strawberry (Fragaria × ananassa Duch.) Ripening

Proanthocyanidins (PAs), also known as condensed tannins, are widespread throughout the plant kingdom, presenting diverse biological and biochemical activities. Being one of the most abundant groups of natural polyphenolic antioxidant, PAs are applied to improve plant tolerance to (a)biotic stresses and delay the senescence of fruit by scavenging the reactive oxygen species (ROS) and enhancing antioxidant responses. The effects of PAs on coloring and softening of strawberries (Fragaria × ananassa Duch.), a worldwide demanded edible fruit and typical material for studying non-climacteric fruit ripening, were firstly assessed in this work. The results showed that exogenous PAs delayed the decrease in fruit firmness and anthocyanins accumulation but improved the fruit skin brightness. Strawberries treated with PAs had similar total soluble solids, total phenolics, and total flavonoids, but lower titratable acidity content. Moreover, the contents of endogenous PAs, abscisic acid and sucrose, were somehow increased by PA treatment, while no obvious change was found in fructose and glucose content. In addition, the anthocyanin- and firmness-related genes were significantly repressed, while the PA biosynthetic gene (anthocyanin reductase, ANR) was highly up-regulated by PA treatment at the key point for fruit softening and coloring. In summary, the results presented in this study suggest that PAs slow down strawberry coloration and softening by inhibiting the expression of related genes, which could be helpful for a better understanding of the biological role of PAs and provide a new strategy to regulate strawberry ripening.

Delaying fruit softening of ‘France’ prune (Prunus domestica L.) using near-freezing temperature storage

To delay ‘France’ prune fruit softening during storage, the effects of near-freezing temperature storage (NFTS; −1.5 ∼ −1 °C) on cell wall polysaccharides, cell-wall-modifying enzyme activities, cell-wall-modifying genes, and tissue ultrastructure of ‘France’ prune fruit were determined. The results showed that NFTS kept a higher fruit firmness (70.9%) compared to the control group (22.6%) at the end of storage. Besides, after 12-day storage, NFTS suppressed the activities of cell-wall-modifying enzymes, the expression of key cell-wall-modifying genes, the dissolution of chelate-soluble pectin (53.1%), Na2CO3-soluble pectin (114.6%), cellulose (81.3%), and hemicellulose (95.2%), and ethylene production (19.7%), and maintained lower water-soluble pectin (38.2%) and lignin contents (16.0%), compared to the control group. Ultrastructural observation showed that NFTS could delay the disassembly of pectin components and protect cell wall structure. In conclusion, NFTS can effectively inhibit fruit softening and maintain fruit quality.

Exogenous salicylic acid regulates organic acids metabolism in postharvest blueberry fruit.

Fruit acidity is an essential factor affecting blueberry organoleptic quality. The organic acid content in blueberry fruit mainly contributes to fruit acidity. This study aims to evaluate the effect of exogenous salicylic acid (SA), the principal metabolite of aspirin, on the organoleptic quality and organic acid metabolism in rabbiteye blueberry (Vaccinium virgatum Ait, 'Powderblue') during cold storage (4 °C). Results showed that SA-treated fruit reduced fruit decay and weight loss delayed fruit softening, and decline of total soluble solids (TSS). TA and total organic acid amounts stayed the same during the late storage period in SA-treated fruit. Four kinds of organic acid components, malic acid, quinic acid, citric acid, and succinic acid, were at higher levels in fruit treated by SA as compared to control. SA enhanced the activities of PEPC, NAD-MDH, and CS to promote the synthesis of malic acid and citric acid. Meanwhile, the activities of NADP-ME, ACL, and ACO, which participated in the degradation of malic acid and citric acid, were inhibited by SA. qPCR results also showed that the expression of VcPEPC, VcNAD-MDH, and VcCS genes were upregulated. In contrast, SA downregulated the expression of VcNADP-ME, VcACL, and VcACO genes. In conclusion, SA could regulate the key genes and enzymes that participated in organic acids metabolism to maintain the freshness of blueberry during cold storage, therefore minimizing the economic loss.

Melatonin alleviates chilling injury and maintains postharvest quality by enhancing antioxidant capacity and inhibiting cell wall degradation in cold-stored eggplant fruit

Melatonin improves the chilling tolerance and quality of postharvest fruit. In this study, we investigated the effect of melatonin on postharvest quality in cold-stored eggplant fruit for 30 d at 5 °C. Melatonin at 100 μmol L−1 was notably effective in decreasing chilling injury (CI) incidence, CI index, weight loss, and in delaying the decrease of lightness, thereby maintaining better postharvest quality of the fruit. Exogenous melatonin inhibited increases in hydrogen peroxide (H2O2), malondialdehyde (MDA), and relative electro-conductivity in the pericarp and pulp, while maintaining higher levels of superoxide dismutase (SOD), catalase (CAT), total polyamines, anthocyanins, and melatonin, as well as the expressions of SOD, CAT1/2, and other genes involved in polyamine biosynthesis (ADC, ODC), melatonin biosynthesis (TDC1, T5H, SNAT1, ASMT, COMT), anthocyanin biosynthesis (PAL, CHS1, CHI, F3H, F3′H, DFR, ANS, 3GT), and cold regulation (COR1, CBF, ZAT2/6/12), thereby conferring the higher chilling tolerance. Melatonin delayed fruit softening and senescence by inhibiting the activities and gene expressions of cell wall degradation enzymes (PME, PG, Cel) and expressions of senescence-associated genes (IAA17, SAG12, SEN4). Overall, these results indicate that melatonin alleviates chilling injury and maintains postharvest quality by enhancing antioxidant capacity and inhibiting cell wall degradation in cold-stored eggplant fruit, which provides a theoretical foundation for extending fruit shelf-life of eggplant during cold storage.

Melatonin Maintains Fruit Quality and Reduces Anthracnose in Postharvest Papaya via Enhancement of Antioxidants and Inhibition of Pathogen Development.

Papaya fruit is widely grown in tropical regions because of its sweet taste, vibrant color, and the huge number of health benefits it provides. Melatonin is an essential hormone that governs many plants′ biological processes. In the current study, the impact of melatonin on fruit ripening and deterioration in postharvest papaya fruit was explored. An optimum melatonin dose (400 μmol L−1, 2 h) was found to be effective in delaying fruit softening and reducing anthracnose incidence. Melatonin enhanced antioxidant activity and decreased fruit oxidative injury by lowering superoxide anion, hydrogen peroxide, and malondialdehyde content by enhancing the enzymatic and non-enzymatic antioxidants, and by improving the antioxidant capacity of papaya fruit. Melatonin increased catalase, ascorbate peroxidase, NADH oxidase, glutathione reductase, polyphenol oxidase, superoxide dismutase, and peroxidase activity, as well as induced total phenol, total flavonoid, and ascorbic acid accumulation. Melatonin also enhanced the activity of defense-related enzymes, such as chitinase, 4-coumaric acid-CoA-ligase, and phenylalanine ammonia lyase, while it repressed lipid metabolism. Additionally, melatonin inhibited the development of anthracnose in vitro and in vivo. These findings suggest that exogenous melatonin application improves papaya fruit quality by boosting antioxidant and defense-related mechanisms.

Control of fruit softening and Ascorbic acid accumulation by manipulation of SlIMP3 in tomato.

SummaryPostharvest deterioration is among the major challenges for the fruit industry. Regulation of the fruit softening rate is an effective strategy for extending shelf‐life and reducing the economic losses due postharvest deterioration. The tomato myoinositol monophosphatase 3 gene SlIMP3, which showed highest expression level in fruit, was expressed and purified. SlIMP3 demonstrated high affinity with the L‐Gal 1‐P and D‐Ins 3‐P, and acted as a bifunctional enzyme in the biosynthesis of AsA and myoinositol. Overexpression of SlIMP3 not only improved AsA and myoinositol content, but also increased cell wall thickness, improved fruit firmness, delayed fruit softening, decreased water loss, and extended shelf‐life. Overexpression of SlIMP3 also increased uronic acid, rhamnose, xylose, mannose, and galactose content in cell wall of fruit. Treating fruit with myoinositol obtained similar fruit phenotypes of SlIMP3‐overexpressed fruit, with increased cell wall thickness and delayed fruit softening. Meanwhile, overexpression of SlIMP3 conferred tomato fruit tolerance to Botrytis cinerea. The function of SlIMP3 in cell wall biogenesis and fruit softening were also verified using another tomato species, Ailsa Craig (AC). Overexpression of SlDHAR in fruit increased AsA content, but did not affect the cell wall thickness or fruit firmness and softening. The results support a critical role for SlIMP3 in AsA biosynthesis and cell wall biogenesis, and provide a new method of delaying tomato fruit softening, and insight into the link between AsA and cell wall metabolism.

Slltpg3, a non-specific lipid transfer protein, acts on the cuticle synthetic pathway to delay water loss and softening of tomato fruit

Non-specific lipid transfer proteins (nsLTPs) are a class of small, omnipresent proteins that are involved in the transport of cuticular wax and other cell wall precursors. Although the cuticle serves as an outer barrier that protects plants from abiotic and biotic stresses and maintains postharvest storage quality, the regulatory role of nsLTPs on the cuticle remains unclear. Here, we isolated the Slltpg3 gene (a member of the tomato nsLTPs family) from tomato (Solanum lycopersicum) and overexpressed Slltpg3 in Micro-Tom tomato cultivars. We found that Slltpg3-overexpression optimized cuticle characteristics by increasing cuticular wax, cutin content, and cuticle thickness and by decreasing cuticle permeability. Our results suggested that Slltpg3 gene is involved in dynamic cuticle synthesis by increasing the content of cuticular wax components and delaying fruit softening and dehydration. Thus, this study revealed a direct relationship between cuticle characteristics and fruit softening and dehydration and provided new insights into tomato adaptation under drought conditions.