Postharvest Tomato Fruit Research Articles

A study on postharvest calcium treatment on chilling injury of tomato fruit

Solanum lycopersicum (tomato) provides a significant amount of vitamins, carotenes, dietary fibres, minerals, and flavonoids, making it a valuable source of nutrients. However, chilling injury (CI) affects tomatoes when the temperature falls below 12°C. Postharvest losses of tomato fruit range from 25% to 42% worldwide, representing losses both in terms of quantity and quality. This study was conducted to evaluate the effectiveness of calcium chloride (CaCl2) treatments on tomato fruit’s CI and the physicochemical quality of postharvest tomato fruit with CaCl2 treatment. Different strengths of CaCl2 (0.5, 2.5, and 4.5% w/v) and control (distilled water) were prepared, and the fruits were soaked for 10 mins as a calcium treatment. Tomato fruits were stored at (5±1°C) prior to the physicochemical analysis; the percentage of chilling injury, surface pitting, weight loss, pH, total soluble sugar (TSS), and concentration of vitamin C was determined at 0, 7, 14, 28 and 42 days of storage. The data significance was analysed by ANOVA test. The result showed that the higher concentration of CaCl2 can significantly decrease (p<0.05) the chilling injury symptom of the tomato fruit for all treatments. The treatment of 4.5% w/v of CaCl2 at days 28 and 42 was found to have a lower CI symptom with (0.66±0.01%) and (1.20±0.01%) respectively. The other physicochemical characteristics were also changed along the treatment of CaCl2.

Resveratrol and nitric oxide synergistically enhance resistance against B. cinerea in tomato fruit by regulating phytohormones

Resveratrol (RVT), a plant antitoxin, plays an important role in plant resistance against pathogens. While nitric oxide (NO) as an essential signaling factor in disease resistance enhancement is well documented, the potential molecular interplay RVT and NO in postharvest tomato fruit defense against Botrytis cinerea (B.cinerea) still needs exploration. In this study, exogenous RVT reduced gray mold caused by B.cinerea in tomato fruit, with 20 μM being the most effective. Tomato fruit were treated with 20 μM RVT enhanced resistance against B.cinerea, as indicated by reduced symptoms of disease and improved activity of disease resistance related enzymes (PAL, PPO and CHI). In addition, RVT treatment improved the expression of SlPR1, SlLoxd and SlMYC2, and promoted the accumulation of plant hormone IAA and ABA, but reduced the expression of SlNPR1 and the level of GA3. More importantly, the combined treatment of NO donor (SNP) and RVT notably enhanced disease resistance compared to RVT or SNP single treatment. However, the combination of NO inhibitor (L-NNA) and RVT treatment even reduced the positive effect of RVT. Meanwhile, the expression of SlPR1, SlLoxd and SlMYC2 and the accumulation of IAA and ABA in RVT + SNP treated fruit were higher than those in the RVT or SNP single treatment. Thus, our data demonstrate that RVT and NO synergistically enhance resistance against B. cinerea in tomato fruit by regulating phytohormones.

Effect of lemongrass and chili pepper oils on the quality of ripe tomato fruits stored under tropical ambient temperature

Postharvest quality of tomato (Solanum lycopersicum L.) fruits treated with lemongrass (Cymbopogon citratus L.) and chili pepper (Capsicum annuum L.) oil was evaluated. Tomato variety Roma fruits of uniform size and weight at the red stage of ripening were overlaid with lemongrass oil only (L1P0), chili pepper oil only (L0P1), or mixtures in a ratio 1:1 (L1P1), and 1:2 (L1P2 and L2P1). Control (L0P0) was not treated with any oil. Treated and untreated fruits were stored at 280±20C and 46%±2 RH for 12 days. Treatments L1P0 and L2P1 oil inhibited postharvest tomato fruit rot for 12 days, whereas L1P2, L0P1, and L1P1 oil and the control showed rot within the range of 86.6% - 100% in 12 days. L1P0 and L2P1 also slowed fruit softening and significantly reduced weight loss, though L1P0 was the most protective. Total soluble solid content of fruit was not affected by both L1P0 and L2P1 throughout storage, but the parameter reduced significantly (p<0.05) in fruits treated with L1P1, L1P2, L0P1 and in control. Reduction in titratable acidity during storage was least in fruits treated with L1P0 followed by L2P1, compared to that in other treatments and the control. This study showed that lemongrass oil applied as surface coating preserved tomato fruit quality in tropical ambient storage conditions for 12 days.

In vitro and in vivo antifungal activity of different bacterial isolates against Botrytis gray mold of tomato

Gray mold rot, caused by Botrytis cinerea, is considered as one of the most harmful fungal diseases affecting postharvest tomato fruits. In the current work, we explore the biocontrol potential of 174 bacterial strains isolated from tomato rhizosphere, argan rhizosphere and a vermicompost to control this fungal pathogen. The in vitro dual culture study of isolated bacterial strains and the fungus-causing pathogen revealed that 31 isolates exhibited a substantial antifungal activity against B. cinerea mycelial growth. The inhibition rates ranged from 55.36 to 85.07%. Twelve bacterial strains which showed the highest antifungal properties (more than 79.6%) were subsequently investigated for their ability to produce compounds with antifungal activity, including diffusible substances, volatile compounds and hydrocyanic acid. These strains were then evaluated in vivo for their ability to reduce fruit decay caused by the fungus. Indeed, isolates VC-B1 (from vermicompost), RS-TB3, and RS-T6 (from the rhizosphere of tomato root), and RH-TB11 (from the tomato rhizoplane) released the most active diffusible substances, which totally inhibited the mycelial growth of B. cinerea. In addition, bacterial strains RS-TB1 and RS-T6 isolated both from the tomato rhizospheric soil were among the isolates that produced the most effective volatile compounds. They reduced the mycelial growth of the fungal pathogen by 75.36% ± 7.24% and 72.94 ± 4.129% respectively. Moreover, RS-TB3, RS-TB4, RH-TB1, and VC-B1 exhibited the highest production of hydrocyanic acid, followed by RS-TB1, VC-3, and VC-13. In vivo bioassays showed disease reduction ranging from 37.92% to 93.14%, with VC-1, VC-5, and RS-T4 showing the highest efficacy. This study identifies several bacterial strains with high potential for biocontrol of B. cinerea in postharvest tomatoes, presenting a promising alternative to chemical fungicides for managing gray mold rot.

SlATG5 is crucial for the accumulation of ROS in postharvest tomato fruit resistance to B.cinerea mediated by nitric oxide

Autophagy is a highly conserved intracellular degradation process that effectively eliminates damaged cells caused by various stresses, including pathogens. While nitric oxide (NO) as the initial signaling molecule in enhancing disease resistance is known, the potential molecular mechanism between autophagy and NO remains elusive. In this study, knockout of SlATG5 intensified the symptoms of disease and promoted the accumulation of reactive oxygen species (ROS). In addition, NO increased the expression of SlATG5, and the absence of SlATG5 also reduced the content of NO and the activity of NOS enzyme. More importantly, knockout of SlATG5 reduced the positive role of NO in disease resistance, which is accompanied with lower enzyme activity of CHI and PPO, and higher level of ROS in SNP+slatg5 compared to SNP+WT. In addition, SlATG5 induced the response of ethylene and auxin signaling. After the deletion of SlATG5, the expressions of ethylene receptors ETR3 and ETR5 were significantly up-regulated, and the auxin-related genes SlIAA1, SlIAA12, and SlIAA17 were significantly inhibited. Thus, our data demonstrate that SlATG5 participates in NO-induced tomato fruit resistance against B.cinerea and induces the response of ethylene and auxin signaling.

The ERF transcription factor SlERF7 promotes UV-C-induced biosynthesis of phenolic compounds in tomato

In this study, the molecular pathways of SlERF7 in regulating the synthesis and accumulation of phenolic compounds induced by postharvest UV-C in tomato fruit was deeply investigated by constructing transgenic plants. The findings revealed a pronounced induction of phenolic compounds accumulation following UV-C irradiation, coupled with heightened activities of PAL, 4CL, C4H, CHS, and CHI enzymes, alongside upregulated expression levels of SlPAL5, SlC4H, Sl4CL, SlCHS2, and SlCHI within SlERF7 overexpressed fruit. Conversely, SlERF7 knockout fruit exhibited diminished levels of phenolic compounds, enzyme activities, and gene expression after UV-C irradiation. Furthermore, subcellular localization analysis showed that SlERF7 was localized in the nucleus. Dual luciferase assay and electrophoretic mobility shift assay (EMSA) indicated that SlERF7 directly bound to the GCC-box in the SlPAL5 promoter and activated its transcriptional activity. Therefore, it was confirmed that SlERF7 might positively promote UV-C-induced phenolic biosynthesis in postharvest tomato fruit by targeting the promoter of SlPAL5.

The Crucial Role of SlGSNOR in Regulating Postharvest Tomato Fruit Ripening.

S-nitrosoglutathione reductase (GSNOR) is a well-known regulator in controlling protein S-nitrosylation modification and nitric oxide (NO) homeostasis. Here, a GSNOR inhibitor N6022 and SlGSNOR silencing were applied to investigate the roles of SlGSNOR in tomato fruit postharvest ripening. We found that the application of N6022 and S-nitrosoglutathione (GSNO, a NO donor), and SlGSNOR silencing delayed the transition of fruit skin color by improving total chlorophyll level by 88.57%, 44.78%, and 91.03%, respectively. Meanwhile, total carotenoid and lycopene contents were reduced by these treatments. Concurrently, the activity of chlorophyll biosynthesis enzymes and the expression of related genes were upregulated, and the transcript abundances of total carotenoid bioproduction genes were downregulated, by N6022 and GSNO treatments and SlGSNOR silencing. In addition, fruit softening was postponed by N6022, GSNO, and SlGSNOR silencing, through delaying the decrease of firmness and declining cell wall composition; structure-related enzyme activity; and gene expression levels. Furthermore, N6022, GSNO, and SlGSNOR silencing enhanced the accumulation of titratable acid; ascorbic acid; total phenol; and total flavonoid, but repressed the content of soluble sugar and soluble protein accompanied with the expression pattern changes of nutrition-related genes. In addition, the endogenous NO contents were elevated by 197.55%; 404.59%; and 713.46%, and the endogenous SNOs contents were enhanced by 74.65%; 93.49%; and 94.85%; by N6022 and GSNO treatments and SlGSNOR silencing, respectively. Altogether, these results indicate that SlGSNOR positively promotes tomato postharvest fruit ripening, which may be largely on account of its negative roles in the endogenous NO level.

The phytocytokine systemin enhances postharvest tomato fruit resistance to Botrytis cinerea

The 18-amino acid peptide systemin is the first identified phytocytokine and plays important roles in tomato resistance to pathogens and insects. However, the function of systemin in postharvest fruit is unknown. Here, we found pretreatment of systemin increased the resistance of postharvest tomato fruit to Botrytis cinerea and the resistance ability was dependent on the concentration of systemin. As a phytocytokine, systemin induced the early immune responses in postharvest fruit, including the expression of immune-related genes, activation of mitogen-activated protein kinases (MAPKs), and production of reactive oxygen species. Transcriptome results indicated that systemin enhanced the expression of genes in the MAPK signaling pathway, phenypropanoid biosynthesis pathway and fatty acid desaturase (FAD) genes. Moreover, systemin regulated the activity of chitinase, phenylalanine ammonia lyase and peroxidase, and the concentration of FAD2 during storage. Therefore, our findings suggested that systemin could be a promising molecule to increase tomato fruit resistance against pathogens during storage.

Antifungal Activity of Streptomyces spp. Extracts In Vitro and on Post-Harvest Tomato Fruits against Plant Pathogenic Fungi

Plant pathogenic fungi are the most important cause of losses in agriculture. In the context of the overuse of synthetic fungicides, natural products are an encouraging alternative to control these plant pathogenic fungi. In this study, we tested the antifungal capacity of four strains of the genus Streptomyces against the plant pathogenic fungi Alternaria alternata, Botrytis cinerea and Fusarium oxysporum. We also investigated the effect of applying the extracts with the highest antifungal activities in a post-harvest setting for the control of B. cinerea on cherry tomato fruits. The results revealed the ability of these strains, especially Streptomyces netropsis A52M, to inhibit in vitro the growth and, in some cases, the sporulation of plant pathogenic fungi. The protective effect of the S. netropsis A52M extracts on post-harvest cherry tomato fruits infected with B. cinerea was demonstrated. In addition, when grown in co-culture, we observed an interesting phenomenon in which the Streptomyces mycelium physically encapsulated the fungal mycelium, contributing to its inhibition. This outcome offers the potential for research into the role of physical microbial interactions in fungal biocontrol. To sum up, the findings outlined here for the interactions between Streptomyces strains and plant pathogenic fungi are a promising, safer, and more sustainable biocontrol alternative to chemicals for agriculture. This is of particular interest in the protection of perishable agricultural products during the post-harvest phase.

Molecular characteristics of some Botrytis isolates and antagonistic activity of Bacillus subtilis and its bacteriocin on tomato fruit

Gray mold, caused by Botrytis cinerea, is one of the most devastating agricultural diseases during the pre and postharvest stages. This study aims to investigate the application of Bacillus subtilis as a bioagent against B. cinerea and reducing pre and postharvest disease as a replacement method to chemical pesticides. Five Botrytis isolates were molecularly confirmed and the virulent isolate BC2 was registered for the first time in the National Center of Biotechnology Information (NCBI) with accession number OP257237. The mycelial growth of B. cinerea was inhibited by up to 84% when treated with the bio agent bacterium using the double drawing method in Petri plates. Pre-harvest application of B. subtilis at a concentration of 108/ml CFU reduced postharvest -gray mold of tomato fruit during ripening stages in the greenhouse. Preharvest application of bioagent bacterium B. subtilis induced the levels of B-1, 3-glucanase and Polyphenol oxidase, indicating enhanced plant resistance to gray mold. Disease severity was decreased compared with control and extended the shelf life at 25 °C.The field application of the bio agent bacterium at the maturity of ripening in preharvest had a significant effect on increasing the level of polyphenol oxidase PPO and B-1, 3-glucanase, which are related to the enhancement of plant defenses and resistance. Additionally, it led to an increase in storage life and a reduction in post-harvest losses. The results demonstrated that preharvest application of bio agent bacterium Bacillus subtilis improved the quality of postharvest tomato fruit and significantly reduced gray mold incidence, all without the use of chemical pesticides.

Combined application of oligochitosan and Pichia carrbbica improves the disease resistance of postharvest tomato fruits

Our previous study showed that postharvest treatment of tomato with Pichia caribbica along with oligochitosan (OCH) significantly alleviated postharvest black spot of tomato fruit compared with P. caribbica alone. This study was to explore the effect of combined application of OCH and P. caribbica on disease resistance of tomato fruits through analyzing the activities of disease resistance-related enzymes, as well as transcriptome analysis of the fruit gene expression. Our findings indicated that P. caribbica, together with OCH, improved the activities of key enzymes associated with disease resistance in tomato fruit. Moreover, the combined application further upregulated the expression of genes involved in α-linolenic acid metabolism, the signal transduction pathways such as Ca2+, MAPK and plant hormone signaling pathways, resistant substance synthesis, and ROS metabolism, which improved the fruit disease resistance. Considering the significance of these results, OCH hold great potential for use in microbial biocontrol strategies against postharvest tomato diseases.

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

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

D-cysteine desulfhydrase silence influences the level of sugar, organic acid, carotenoids, and polyphenols in tomato fruit

Hydrogen sulfide (H2S) plays important roles in the regulation of fruit ripening. D-cysteine desulfhydrase (DCD) is one of the key enzymes of H2S synthesis. However, whether and how DCD is involved in the regulation of tomato fruit quality is still unknown. Here, the tobacco rattle virus (TRV)-based virus-induced gene-silencing (VIGS) was used to silence DCD to explore the effect of DCD on quality regulation in postharvest tomato fruit. The results revealed that DCD silence accelerated the accumulation of fructose, glucose, soluble sugar, soluble protein, carotene, and lycopene. The expressions of the major genes (PFPP, ATPPF, FBA6; GPI, GPD1, POL2; ZDS, CCD7, CrtL-e-1, psy1, LCY1 and PDS) in sugar, acid and carotene metabolism were up-regulated in DCD-silenced tomatoes. DCD silence also decreased the content of malic acid, citric acid, ascorbic acid, total phenols, and total flavonoid by reducing the transcriptional level of their metabolism related genes (MDH, ME1, ME2; CSG, CS3, CSM; MDHAR and DHAR1; PAL5, 4CL, CHS2 and F3H). Meanwhile, the effects of DCD silence on tomato fruit were reversed by the addition of H2S. Thus, H2S might regulate the quality of postharvest tomato fruit through a DCD-dependent pathway.

Quantitative proteomic analysis of tomato fruit ripening behavior in response to exogenous abscisic acid.

To determine how abscisic acid (ABA) affects tomato fruit ripening at the protein level, mature green cherry tomato fruit were treated with ABA, nordihydroguaiaretic acid (NDGA), or sterile water (control, CK). The proteomes of treated fruit were analyzed and quantified using tandem mass tags (TMTs) at 7 d after treatment, and the gene transcription abundances of differently expressed proteins (DEPs) were validated with qRT-PCR. The postharvest tomato fruit underwent faster color transformation and ripening than the CK when treated with ABA. In total, 6310 proteins were identified among the CK and treatment groups, of which 5359 were quantified. Using a change threshold of 1.2 or 0.83 times, 1081 DEPs were identified. Among them, 127 were upregulated and 127 were downregulated in the ABA vs CK comparison group. According to KEGG and protein-protein interaction network analyses, the ABA-regulated DEPs were primarily concentrated in the photosynthesis system and sugar metabolism pathways, and 102 DEPs associated with phytohormones biosynthesis and signal transduction, pigment synthesis and metabolism, cell wall metabolism, photosynthesis, redox reactions, allergens, and defense responses were identified in the ABA vs CK and NDGA vs CK comparison groups. ABA affects tomato fruit ripening at the protein level to some extent. The results of this study provided comprehensive insights and datas for further research on the regulatory mechanism of ABA in tomato fruit ripening. This article is protected by copyright. All rights reserved.

Overexpression of PPtase in Streptomyces sp. NAUS: Increasing biocontrol potential against postharvest tomato fruit decay and isolation of a novel antifungal compound

Streptomyces species are considered promising biological control strains since they produce various antimicrobial substances to control diseases in fruit and vegetables. Many Streptomyces species' biosynthetic gene clusters (BGCs) are silent when subjected to conventional laboratory conditions. Therefore, activating these BGCs is crucial for developing effective strategies for controlling postharvest phytopathogens. In the present study, phosphopantetheinyl transferase (PPtase) genes were overexpressed in 20 actinomycetes isolated from the soil rhizosphere of Osmanthus fragrans to trigger cryptic BGCs. The genomic comparison between the highly proficient actinomycete (strain NAUS) and Streptomyces albiflaviniger DSM 42598T yielded an average nucleotide identity (ANI) exceeding 95%, indicating that the strain belongs to the same species. The NAUS - PPtase-overexpressed strain exhibited 4.7 times higher antifungal activity than the wildtype strain against Penicillium citrinum. Its fermented extracts remarkably reduced postharvest tomato fruit decay by 89.71%. A novel ionophore compound with outstanding antimicrobial activity was identified based on spectroscopic and chemical methods. The enhanced antifungal activities and biocontrol efficacy can be attributed to activated secondary metabolites in the PPtase-overexpressed S. albiflaviniger strain, highlighting the usefulness of this pipeline for biocontrol of pathogenic fungi and bacteria.

The MADS-box protein SlTAGL1 regulates a ripening-associated SlDQD/SDH2 involved in flavonoid biosynthesis and resistance against Botrytis cinerea in post-harvest tomato fruit.

3-Dehydroquinate dehydratase/shikimate dehydrogenase (DQD/SDH) is a key rate-limiting enzyme that catalyzes the synthesis of the shikimate, which is an important metabolic intermediate in plants and animals. However, the function of SlDQD/SDH family genes in tomato (Solanum lycopersicum) fruit metabolites is still unknown. In the present study, we identified a ripening-associated SlDQD/SDH member, SlDQD/SDH2, that plays a key role in shikimate and flavonoid metabolism. Overexpression of this gene resulted in an increased content of shikimate and flavonoids, while knockout of this gene by CRISPR/Cas9 mediated gene editing led to a significantly lower content of shikimate and flavonoids by downregulation of flavonoid biosynthesis-related genes. Moreover, we showed that SlDQD/SDH2 confers resistance against Botrytis cinerea attack in post-harvest tomato fruit. Dual-luciferase reporter and EMSA assays indicated that SlDQD/SDH2 is a direct target of the key ripening regulator SlTAGL1. In general, this study provided a new insight into the biosynthesis of flavonoid and B. cinerea resistance in fruit tomatoes.

Overexpression of Sly-miR167a delayed postharvest chilling injury of tomato fruit under low temperature storage

Chilling injury (CI) of tomato fruit leads to the deterioration of fruit quality, thereby shortening the shelf life of tomato fruit. The present experiment investigates the effect of Sly-miR167a on postharvest cold tolerance of tomato fruit. Results demonstrated that overexpression of Sly-miR167a in tomato fruit effectively reduced electrolyte leakage (EL), hydrogen peroxide (H2O2) content, malondialdehyde (MDA) content and CI index during low temperature storage. Compared with wild-type (WT) and the silencing miR167a by short tandem target mimic (miR167a-STTM) fruit, overexpression of Sly-miR167a (miR167a-OE) fruit accumulated more ascorbic acid (AsA), proline, lycopene, and phenolics, and also maintained higher activities of antioxidant enzymes. At low temperatures, miR167a-OE fruit sustained better quality, and had lower expression levels of ARF6a, higher levels of ethylene production and higher expression levels of CBF1. Overexpression of Sly-miR167a delayed the appearance of CI symptoms, improving the chilling tolerance of postharvest tomato fruit.

Biological control of gray mold of tomato by Bacillus altitudinis B1-15

Gray mold, caused by Botrytis cinerea, is one of the most serious and widespread diseases that affect tomato plants and fruit and reduce yield. In the present study, Bacillus altitudinis B1-15 isolated from saline-alkali soil showed strong antifungal activity against B. cinerea. In pot experiments, a significant biocontrol efficacy of strain B1-15 was observed against tomato gray mold at 3-leaf stage (87.63%) and 6-leaf stage (76.43%), and the biocontrol efficacy was found to be 39.83% even after inoculation for 35 d at 6-leaf stage. A significant improvement of stem diameter, plant height, dry weight and fresh weight was also observed after tomato plants inoculated with strain B1-15. Strain B1-15, applied to tomato fruit by wounded or unwounded inoculation, could significantly inhibit gray mold and prolong the storage period of postharvest tomato fruit. The antifungal substances of strain B1-15 were found both in intraspore and extraspore, and the strain was also able to produce volatile organic compounds (VOCs), which could cause the mycelia of B. cinerea swelling and dehydrated malformation, the shortening of mycelia septum and the decomposition of cell wall and vacuole. Besides that, strain B1-15 could produce protease at a greater level, and chitinase and amylase at a lower level, which contributed to its antifungal activity. Additionally, 15 and 9 chemical compounds (similarity ≥ 80%) were individually identified from the crude extracts of the supernatant and precipitate of strain B1-15 via gas chromatography-mass spectrometry (GC–MS), including two VOCs 3-methylbutanoic acid and 2-methylbutanoic acid detected in both the supernatant and precipitate. Therefore, strain B1-15 could be used as a biocontrol agent and has great potential to control tomato gray mold and improve tomato yield and storage quality in practical production.

SlMAPK3 Positively Regulates the Ethylene Production of Postharvest Tomato Fruits and Is Involved in Ethylene-Mediated Cold Tolerance.

Mitogen-activated protein kinase (MAPK) cascades and ethylene are crucial for plant growth, development, and stress responses, but their potential mechanisms in cold resistance remain unclear. We revealed that SlMAPK3 transcript levels were dramatically induced by cold treatment in an ethylene-dependent manner. Under cold stress, the proline content of SlMAPK3-overexpression fruit was 96.5 and 115.9% higher than that of wild-type fruit (WT), respectively, while the ion leakage was 37.3 and 32.5% lower than that of WT. RNA sequencing revealed that overexpression of SlMAPK3 caused upregulation of genes that are enriched in the ethylene-activated signaling pathway (GO:0009873), cold signaling pathway (GO:0009409), and heat signaling pathway (GO:0009408). RT-qPCR demonstrated that the expression levels of SlACS2, SlACS4, SlSAHH, SlCBF1, SlDREB, SlGolS1, and SlHSP17.7 in the OE.MAPK3 fruits were consistent with the RNA sequencing results. Meanwhile, the knockout of SlMAPK3 reduced the ethylene content, ACC content, and ACS activity. Moreover, the knockout of SlMAPK3 reduced the positive effect of ethylene in cold stress, while suppressing the expression of SlICE1 and SlCBF1. In conclusion, our study demonstrated a novel mechanism by which SlMAPK3 positively regulates the ethylene production of postharvest tomato fruits and is involved in ethylene-mediated cold tolerance.

Ellagic Acid Treatment Improves Postharvest Quality of Tomato Fruits by Enhancing the Antioxidant Defense System

Ellagic acid (EA) is a bioactive polyphenol compound with numerous biological activities, such as anti-inflammatory, antiestrogenic, antioxidant, and anticancer activities. In this research, we investigated the effect of postharvest tomato fruits with EA treatment. Our results showed that at 25°C for 20 days, compared to a control group, the weight loss rate, titratable acidity, and soluble solid concentration of tomato fruits treated with 50 μM EA were lower. The content of soluble protein in the EA-treated group was approximately 1.65 times higher than in the control group, and EA treatment greatly inhibited the changes in lycopene and vitamin C content. Moreover, EA treatment reduced malondialdehyde content, electrolyte leakage, and the production of reactive oxygen species. Furthermore, EA treatment upregulated the expression of antioxidant-related genes and induced the activities of the antioxidant enzyme. In summary, our results showed that EA could retard senescence and preserve the quality characteristics of harvested tomato fruits via enhancing the antioxidant responses.