Phenylalanine Ammonia-lyase Activity Research Articles

The combination of nanoparticles and endophytes boosts Thyme (Thymus vulgaris L.) resistance to drought stress by elevating levels of phenolic compounds, flavonoids, and essential oils

BackgroundAs climate change and water scarcity increasingly threaten agricultural productivity, enhancing plant resilience to drought has attracted great attention. This study explored the potential of combining Fe2O3 nanoparticles (FeNPs), endophytic bacteria (EB), and endophytic fungi (EF) to boost drought tolerance in Thymus vulgaris. The research aimed to assess how these combined treatments affect the plant’s physiological responses and chemical composition under drought stress.ResultsA factorial experiment was designed using completely randomized design (CRD) method, incorporating four irrigation levels [100%, 75%, 50%, and 25% field capacity (FC)], four FeNPs concentrations (0, 0.5, 1, and 1.5 mg L−1), and three endophyte types (control, bacteria, and fungi). After extracting, purifying, identifying, and screening EB and EF from nine Lamiaceae species, the endophytes Azospirillum lipoferum and Aspergillus oryzae isolated from Salvia mirzayanii exhibited the highest drought resistance. The highest amounts of TFM (45.45 g) and TDM (21.56 g) were obtained using the combination of EB and FeNPs at 1 mg L−1 under irrigation with 100% FC. At 25% FC, EB treatment increased the activities of polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) by 62.12% and 18.23% compared to the control, respectively. In addition, under optimal humidity conditions, FeNP concentrations were higher than 0.5 mg L−1 leading to a decrease in PPO activity. At 25% FC, the highest content of total phenols was observed with a 37.5% increase under EB treatment using 1 mg L−1 of FeNPs, while the highest content of total flavonoids showed a 62.72% increase under EF treatment with 0.5 mg/L of FeNPs. The highest level of p-coumaric acid was obtained under EF (34.27% compared to control). At 25% FC, EB and FeNPs (1 mg L−1) increased the level of caffeic acid in thyme plants by 24.70% and 10.08%, respectively. In addition, inoculation with EB increased (11.9%) the content of ferulic acid in plants and the application of FeNPs as a foliar spray decreased the level of ferulic acid in thyme plants. The highest essential oil percentage at 25% FC was observed after inoculation with EF and FeNPs (0.5 mg L−1), resulting in significant increases of 14.7% and 82.12%, respectively, compared to the control. A decrease in irrigation level led to an increase in the percentage of essential oil in thyme plants while decreasing dominant essential oil compounds, thymol, and carvacrol. The levels of thymol and carvacrol in the essential oil were not affected by the interaction effects of drought stress, endophytes, and FeNPs. EF and FeNPs (1.5 mg L−1), respectively, caused significant increases of 17.44% and 29.87% compared to the control in the amount of thymol and significant increases of 13.75% and 31.01% in the amount of carvacrol. All FeNPs concentrations decreased the concentrations of ferulic acid, FeNPs (1.5 mg L−1) and PPO; these particles act as abiotic stressors at sub-toxic levels and become phytotoxic at higher concentrations.ConclusionsIt seems that combining endophytes with FeNPs showed promise in enhancing drought tolerance in T. vulgaris. These treatments have significantly contributed to the production of enzymatic antioxidants, flavonoids, and phenolic compounds, leading to a reduction in the amounts of oxidants. At the same time, they have improved both the quality and quantity of essential oils. This highlights the importance of establishing an effective antioxidant system in response to environmental stresses.Graphical

Effects of Thifluzamide Treatment on the Production of Cell Wall Degrading Enzymes in Rhizoctonia solani and Phenylpropane Metabolism in Pear Fruit

The study aimed to investigate the effects of thifluzamide (2.67 mg/L) on ‘Huangguan’ pear fruit rot caused by Rhizoctonia solani during storage, as well as the activities of polygalacturonase (PG), pectin methylesterase (PME), polygalacturonic acid trans-eliminase (PGTE), pectin methyl trans-eliminase (PMTE), xylanase, and pectate lyase (PL) secreted by R. solani. The results showed that thifluzamide treatment significantly inhibited the activities of PG, PME, PGTE, PMTE, xylanase, and PL secreted by R. solani after 3 days in vitro culture, compared to the control. Thifluzamide also increased the activities of phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), and 4-coumarate CoA ligase (4CL), and the contents of flavonoids and total phenolic compounds in pear fruit. Furthermore, thifluzamide increased the expression of PcPAL, PcC4H, Pc4CL, Pcβ-1,3-GA, PcLCH, PcF3H, and PcDFR involved in phenylpropanoid metabolism in pear fruit. In conclusion, thifluzamide treatment reduced the infection ability of R. solani by inhibiting the expression of the genes encoding cell wall-degrading enzymes in R. solani. At the same time, it inhibited the activities of cell wall-degrading enzymes induced resistance against R. solani infection in ‘Huangguan’ pears by promoting phenylpropane metabolism.

Biochar Organic Fertilizer Combined with Indigenous Microorganisms Enhances the Growth of Landscape Grass Cultivated in a Substrate Mixed with Iron Tailings and Mining Topsoil.

Iron tailings from the mining process occupy vast land areas and pose a significant ecological risk. In order to reuse iron tailings resources and carry out in situ ecological restoration of a mine, in this study, a medium of mixed iron tailings and mining topsoil (m:m = 3:1) was used to plant landscape grasses, including Lolium perenne L. (L. perenne), Pennisetum alopecuroides (L.) Spreng. (P. alopecuroides), Melilotus officinalis (L.) Lam. (M. officinalis), and Medicago sativa L. (M. sativa). Biochar and chicken manure were used as biochar organic fertilizers and indigenous microorganisms were isolated from the rhizosphere soil of tested grasses. They were applied to enhance landscape grass growth by regulating rhizosphere microbial communities and nutrient conditions. The results showed that the biochar organic fertilizers significantly promoted the growth of the four landscape grasses, notably P. alopecuroides, increasing plant height, root length, root weight, and leaf fresh weight by 169%, 60%, 211%, and 388%, respectively. Additionally, L. perenne exhibited the greatest height increase (10%) following the application of bacterial solutions. Moreover, indigenous bacterial solutions enhanced chlorophyll content and phenylalanine ammonia-lyase (PAL) activity, with P. alopecuroides showing the highest chlorophyll increase of 58% and M. sativa exhibiting a 30.58% rise in PAL activity. The biochar organic fertilizer also significantly elevated soluble protein content in P. alopecuroides and M. sativa by 195% and 152%, respectively. It also effectively enhanced peroxidase (POD) activity in Poaceae grasses by 120% to 160%. After adding indigenous microorganisms, the rhizosphere soil of the landscape grass showed the highest Shannon-Wiener diversity index, reaching 3.561. The rhizosphere soil of M. officinalis had the highest microbial richness, with a value of 39. Additionally, the addition of indigenous microorganisms increased the nitrogen, phosphorus, and potassium content of the four plants by 8-19%, 6-14%, and 8-18%, respectively. This study offers a new approach for managing mining waste and ecological restoration in mining areas.

Sodium nitroprusside enhances vase life of Polianthes tuberosa cut flowers by inducing defence enzymes

ABSTRACT The effect of sodium nitroprusside (SNP) in inducing the activity of the defence system enzymes and their role in the vase life of two Polianthes tuberosa cultivars (‘Mahalati’ and ‘Dezfouli’) was investigated. SNP pulsing (150 μM for 0, 24 and 48 h) induced the activity of the antioxidant enzymes, superoxide dismutase (SOD) and peroxidase (POX) up to 6 and 3 days after application, respectively. Also, the activities of phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO) increased in SNP-treated plants until 3 and 6 days after application, respectively. The activity of these enzymes after 48 h pulsing was higher than 24 h pulsing. However, in most cases, there was no statistical difference between these two treatments. The chlorophyll degradation was reduced and the electrolyte leakage and malondialdehyde accumulation in the petals of the SNP-treated plants were limited. These responses increased the vase life and opening rate of the florets. The increased activity of PAL and PPO is probably due to improving antimicrobial activity in the stem and improved vase solution uptake by flowers up to 9 days after the treatments. SNP pulsing for 24 h was suggested for increasing the vase life and quality of P. tuberosa cut flowers.

Efficacy of active modified atmosphere packaging containing thymol on fortification of antioxidant capacity and reducing the microbial contamination of pomegranate arils

Pomegranate arils pose a significant challenge when it comes to preserving their nutritional value and preventing microbial contamination. This study aimed to explore the impact of thymol fumigation and active modified atmosphere packaging (MAP) on enzymatic activity and microbial contamination prevention in pomegranate arils. The results indicated that arils stored in a high O2 atmosphere (HO2A) with thymol had notably different catalase (CAT) and peroxidase (POD) activity levels compared to other treatments. These arils exhibited the highest CAT activity and the lowest POD activity. The highest phenylalanine ammonia-lyase (PAL) activity was observed in arils stored in HO2A with thymol, although it was not significantly different from those stored in a high CO2 atmosphere (HCO2A) with thymol (P<0.05). Arils stored in a low oxygen atmosphere (LO2A) and HCO2A with thymol showed the highest polyphenol oxidase (PPO) activity levels, while arils in HO2A with thymol had the lowest. The HO2A with thymol treatment resulted in the lowest presence of psychrophilic bacteria, although it was not significantly different from arils stored in LO2A with thymol (P<0.01). Based on cluster analysis results, HO2A with thymol, LO2A with thymol, and HCO2A with thymol could be considered the most effective treatments for extending the storage life of packaged pomegranate arils.

Preharvest sodium selenite treatments affect the growth and enhance nutritional quality of purple leaf mustard with abundant anthocyanin.

Both selenium (Se) and anthocyanins are crucial for maintaining human health. Preharvest Se treatments could promote anthocyanin biosynthesis and augment Se levels in vegetables, helping to combat Se deficiencies in dietary intake. However, it remains unknown whether preharvest Se treatment could balance growth and anthocyanin biosynthesis in plants and what the appropriate treatment concentration is. In this study, preharvest treatments with sodium selenite at varying concentrations (0, 5, 10, and 30 mg/kg) affect the growth and nutritional quality of purple leaf mustard (Brassica juncea) with abundant anthocyanins. Lower Se concentrations (≤10 mg/kg) of preharvest treatments enhanced photosynthesis, facilitated root system development, consequently elevated the biomass. Conversely, higher Se levels (≥30 mg/kg) reduced photosynthesis and biomass. The dosage-dependent effects of Se treatments were corroborated through seedlings cultivated in hydroponic conditions. Moreover, nearly all Se treatments elevated the contents of various nutrients in leaf mustard, particularly anthocyanin and organic se. These results suggest an overall enhancement in nutritional quality of leaf mustard plants. Furthermore, the application of 10 mg/kg Se significantly enhanced the activity of phenylalanine ammonia-lyase and upregulated the expression of 12 genes pivotal for anthocyanin biosynthesis, further demonstrating the fortified effects of Se enrichment on anthocyanins in leaf mustard. Low-level Se treatments resulted in heightened antioxidant activity (APX, CAT, and POD), mitigating reactive oxygen species induced by increasing Se content in tissues. The enhanced antioxidant activities may be beneficial for the normal growth of leaf mustard under Se stress conditions. In conclusion, our study demonstrated preharvest Se treatment at 10 mg/kg could balance the growth and anthocyanin biosynthesis in purple leaf mustard. This study offers valuable insights into anthocyanin fortification through Se enrichment methods in agricultural practices, ensuring that such fortification does not compromise leafy vegetable yield.

Chitosan nanoparticles (CSNPs) conferred salinity tolerance in maize by upregulating E3 ubiquitin-protein ligase, P5CS1, HKT1, NHX1, and PMP3 genes.

This study explored the transcriptional behaviors of several candidate genes in response to the application of CSNPs (50 and 100 mgl-1) in maize seedlings grown under two salinity levels (NaCl of 0.07 and 0.14 gkg-1soil). Employing CSNPs at both concentrations mitigated the inhibitory role of salinity on the leaf and root fresh weights. The application of CSNPs enhanced the transcription of the E3 ubiquitin-protein ligase gene by an average of threefold, contrasted with the salinity controls. The Δ1-pyrroline-5-carboxylate synthetase (P5CS1) gene was upregulated in response to both individual and mixed treatments of CSNPs and salinity. The transcription of the high-affinity K+ transporter (HKT1) gene displayed an upward trend in response to the CSNPs and salinity treatments. The Na+/H+ exchangers (NHX1) gene exhibited a similar trend to that of the HKT1 gene. The utilization of CSNPs was accompanied by an upregulation in the plasma membrane proteolipid 3 (PMP3) gene, contrasted with the salinity controls. The phenylalanine ammonia-lyase (PAL) activity displayed an upward trend in response to the foliar application of CSNPs. The CSNPs at the 100 mgl-1 concentration were more capable of inducing the ascorbate peroxidase enzyme under both salinity conditions than the 50 mgl-1 dose. The simultaneous exposure of maize seedlings to CSNPs and salinity resulted in the drastic upregulation of the catalase activities. This study provides novel insights into the major mechanisms underlying the stress-mitigating effects of CSNPs, thereby providing a suitable platform for their application in sustainable agricultural practices.

Nitrogen Level Impacts the Dynamic Changes in Nitrogen Metabolism, and Carbohydrate and Anthocyanin Biosynthesis Improves the Kernel Nutritional Quality of Purple Waxy Maize

Waxy corn is a special type of maize primarily consumed as a fresh vegetable by humans. Nitrogen (N) plays an essential role in regulating the growth progression, maturation, yield, and quality of waxy maize. A reasonable N application rate is vital for boosting the accumulation of both N and carbon (C) in the grains, thereby synergistically enhancing the grain quality. However, the impact of varying N levels on the dynamic changes in N metabolism, carbohydrate formation, and anthocyanin synthesis in purple waxy corn kernels, as well as the regulatory relationships among these processes, remains unclear. To explore the effects of varying N application rates on the N metabolism, carbohydrate formation, and anthocyanin synthesis in kernels during grain filling, a two-year field experiment was carried out using the purple waxy maize variety Jinnuo20 (JN20). This study examined the different N levels, specifically 0 (N0), 120 (N1), 240 (N2), and 360 (N3) kg N ha−1. The results of the analysis revealed that, for nearly all traits measured, the N application rate of N2 was the most suitable. Compared to the N0 treatment, the accumulation and content of anthocyanins, total nitrogen, soluble sugars, amylopectin, and C/N ratio in grains increased by an average of 35.62%, 11.49%, 12.84%, 23.74%, 13.00%, and 1.87% under N2 treatment over five filling stages within two years, respectively, while the harmful compound nitrite content only increased by an average of 30.2%. Correspondingly, the activities of related enzymes also significantly increased and were maintained under N2 treatment compared to N0 treatment. Regression and correlation analysis results revealed that the amount of anthocyanin accumulation was highly positively correlated with the activities of phenylalanine ammonia-lyase (PAL) and flavanone 3-hydroxylase (F3H), but negatively correlated with anthocyanidin synthase (ANS) and UDP-glycose: flavonoid-3-O-glycosyltransferase (UFGT) activity, nitrate reductase (NR), and glutamine synthetase (GS) showed significant positive correlations with the total nitrogen content and lysine content, and a significant negative correlation with nitrite, while soluble sugars were negatively with ADP-glucose pyrophosphorylase (AGPase) activity, and amylopectin content was positively correlated with the activities of soluble starch synthase (SSS), starch branching enzyme (SBE), and starch debranching enzyme (SDBE), respectively. Furthermore, there were positive or negative correlations among the detected traits. Hence, a reasonable N application rate improves purple waxy corn kernel nutritional quality by regulating N metabolism, as well as carbohydrate and anthocyanin biosynthesis.

Exploring the antifungal activity of clove oil (Syzygium aromaticum) against wilt disease caused by Fusarium equiseti in bitter gourd (Momordica charantia L.)

This study investigates the isolation and characterization of Fusarium equiseti, a fungal pathogen causing wilt in bitter gourd. It explores the antifungal activity of essential oils, particularly clove oil, as a natural management approach. The pathogen was isolated from wilt-infected bitter gourd stems and it was confirmed as F. equiseti morphologically by the presence of three-septate falcate macroconidia and globose microconidia and also confirmed molecularly by PCR amplification of the ITS region (PP501044.1). Among the tested essential oils, clove oil demonstrated the highest mycelial growth inhibition (100%) at a concentration of 0.5%, followed by peppermint, wintergreen and tea tree oils. In comparison, neem oil exhibited the least inhibition (15.54%). GC-MS analysis of clove oil revealed 38 compounds, where eugenol is the predominant compound that played a crucial role in antifungal activity. Additionally, metabolic analysis revealed several enriched pathways in F. equiseti during its interaction with clove oil, particularly those involved in lipid metabolism and energy production. Pot culture experiments confirmed the efficacy of clove oil in reducing disease severity and incidence in bitter gourd, achieving a 66.99 % reduction when combined with soil application.Furthermore, clove oil-treated plants showed increased activity of defense-related enzymes, including peroxidase (PO), polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL), suggesting the induction of systemic resistance. This study highlights the potential of clove oil as an eco-friendly alternative to synthetic fungicides for managing F. exquisite-induced wilt in bitter gourd. Future research should focus on optimizing clove oil application methods and understanding its interactions with fungal pathogens at the molecular level to enhance its efficacy in sustainable disease management.

Spraying glycine betaine on fresh pistachio fruits (Pistacia vera L.) for preservation in cold storage

Oxidative stress occurs during storage, often leading to a decrease in fruit quality and subsequently reducing its marketability. In this investigation, the ability of glycine betaine (GB) to extend the quality and storage of fresh pistachios stored in cold conditions was evaluated. The independent variables in this study were the concentration of GB (0, 5, 10 and 15 mM) and storage period (at harvest, 25, 50, and 75 days after harvest). Over time, the chlorophyll and carotenoid content of both kernels and hulls, as well as phenolics, flavonoids, antioxidant activity, taste, aroma, appearance of shells and hulls, firmness, and overall weight, tend to decrease. However, glycine betaine (GB) significantly prevents these reductions. GB effectively countered the rise in malondialdehyde, ion leakage, and hydrogen peroxide levels in kernels over time. In GB-treated samples, anthocyanin levels initially increased when comparing harvest time in both kernels and hulls, but subsequently decreased. GB enhanced peroxidase activity and suppressed polyphenol oxidase activity. However, contrary to expectation, GB reduces phenylalanine ammonia lyase activity. Overall, higher GB concentrations lead to a more pronounced effect. Based on the results, GB, particularly at a concentration of 15 mM, is recommended for preserving fresh pistachios during cold storage.

Methyl salicylate induces endogenous jasmonic acid and salicylic acid in 'Nam Dok Mai' mango to maintain postharvest ripening and quality

Salicylic acid (SA) and jasmonic acid (JA) are indispensable phytohormones whose interaction influences the ripening process in plants. Methyl salicylate (MeSA) and methyl jasmonate (MeJA) have been utilized to elevate the endogenous levels of SA and JA in horticultural products after harvest. However, their ability to preserve mango is uncertain. Individually and combined effects of exogenous MeSA and MeJA on mango ripening quality were investigated. 'Nam Dok Mai' mangoes were fumigated with MeSA, MeJA, and MeSA plus MeJA (MeSAJA) prior to storage for 6 d at 25 °C and 80–85% relative humidity (RH). Fruit ripening attributes, respiration rate, ethylene (ET) production, total phenolics (TP), and malondialdehyde (MDA) were assessed. Endogenous SA and JA levels were measured, as were the activities of lipoxygenase (LOX) and phenylalanine ammonia-lyase (PAL), and the expression of related genes MiPAL, MiICS, and MiLOX. Individual application of MeSA or MeJA preserved the mango quality by reducing ET production, respiration rate, and MDA levels while raising TP shortly after treatment. The ripening quality mirrored the induced SA and JA levels and correlated with the high expression of biosynthetic-related genes (MiPAL, MiICS, and MiLOX). Individual treatments stimulated SA and JA biosynthesis, demonstrating that these phytohormones are functionally connected and interdependent. When combined, MeSAJA caused a tradeoff response and distinct phenotypic outcomes compared to the individual treatments. As a result, MeSA fumigation is a practical method for preserving mango quality after harvest.

A hierarchical ubiquitination-mediated regulatory module controls bamboo lignin biosynthesis

Abstract The lignocellulosic feedstock of woody bamboo shows promising potential as an alternative to conventional wood, attributed to its excellent properties. The content and distribution of lignin serve as the foundation of these properties. While the regulation of lignin biosynthesis in bamboo has been extensively studied at the transcriptional level, its posttranslational control has remained poorly understood. This study provides a ubiquitinome dataset for moso bamboo (Phyllostachys edulis), identifying 13015 ubiquitinated sites in 4849 unique proteins. We further identified Kelch repeat F-boxprotein 9 (PeKFB9) that plays a negative role in lignin biosynthesis. Heterologous expression of PeKFB9 resulted in reduced accumulation of lignin and decreased phenylalanine ammonia-lyase (PAL) activities. Both in vitro and in vivo assays identified interaction between PeKFB9 and PePAL10. Further examination revealed that SCFPeKFB9 mediated the ubiquitination and degradation of PePAL10 via the 26S proteasome pathway. Moreover, PebZIP28667 could bind to the PePAL10 promoter to significantly inhibit its transcription, and ubiquitination of PebZIP28667 weakened this inhibition. Collectively, our findings reveal a PeKFB9-PePAL10/PebZIP28667-PePAL10 module that acts as a negative regulator of lignin biosynthesis. This study advances our understanding of posttranslational regulation in plant lignification, which will facilitate the improvement of the properties of bamboo wood and the breeding of varieties.

Silicon-mediated resilience: Unveiling the protective role against combined cypermethrin and hymexazol phytotoxicity in tomato seedlings

Insecticides and fungicides present potential threats to non-target crops, yet our comprehension of their combined phytotoxicity to plants is limited. Silicon (Si) has been acknowledged for its ability to induce crop tolerance to xenobiotic stresses. However, the specific role of Si in alleviating the cypermethrin (CYP) and hymexazol (HML) combined stress has not been thoroughly explored. This study aims to assess the effectiveness of Si in alleviating phytotoxic effects and elucidating the associated mechanisms of CYP and/or HML in tomato seedlings. The findings demonstrated that, compared to exposure to CYP or HML alone, the simultaneous exposure of CYP and HML significantly impeded seedling growth, resulting in more pronounced phytotoxic effects in tomato seedlings. Additionally, CYP and/or HML exposures diminished the content of photosynthetic pigments and induced oxidative stress in tomato seedlings. Pesticide exposure heightened the activity of both antioxidant and detoxification enzymes, increased proline and phenolic accumulation, and reduced thiols and ascorbate content in tomato seedlings. Applying Si (1 mM) to CYP- and/or HML-stressed seedlings alleviated pigment inhibition and oxidative damage by enhancing the activity of the pesticide metabolism system and secondary metabolism enzymes. Furthermore, Si stimulated the phenylpropanoid pathway by boosting phenylalanine ammonia-lyase activity, as confirmed by the increased total phenolic content. Interestingly, the application of Si enhanced the thiols profile, emphasizing its crucial role in pesticide detoxification in plants. In conclusion, these results suggest that externally applying Si significantly alleviates the physio-biochemical level in tomato seedlings exposed to a combination of pesticides, introducing innovative strategies for fostering a sustainable agroecosystem.

Antifungal mechanisms and characteristics of Pseudomonas fluorescens: Promoting peanut growth and combating Fusarium oxysporum-induced root rot

Continuous cropping of peanuts presents significant challenges to sustainable production due to soil-borne diseases like root rot caused by Fusarium species. In this study, field inoculation experiments treatments and in vitro agar plate confrontation tests were conducted, including non-inoculated controls (CK), inoculation with Pseudomonas fluorescens (PF), Fusarium oxysporum (FO), and co-inoculation with both (PF + FO). The aim was to explore the antifungal mechanisms of Pseudomonas fluorescens in mitigating root rot and enhancing peanut yield. The results indicated that PF and PF + FO significantly enhanced peanut root activity, as well as superoxide dismutase, catalase, and glutathione S-transferase activities, while simultaneously decreasing the accumulation of reactive oxygen species and malondialdehyde contents, compared to FO treatment. Additionally, PF treatment notably increased lignin content through enhanced phenylalanine ammonia lyase, cinnamate 3-hydroxylase, and peroxidase activity compared to CK and FO treatment. Moreover, PF treatment resulted in longer roots and a higher average diameter and surface area, potentially due to increased endogenous levels of auxin and zeatin riboside, coupled with decreased abscisic acid content. PF treatment significantly elevated chlorophyll content and the maximum photochemical efficiency of PSII in the light-adapted state, the actual photochemical efficiency and the proportion of PSII reaction centers open, leading to improved photosynthetic performance. Confrontation culture assays revealed PF's notable inhibitory effects on Fusarium oxysporum growth, subsequently reducing rot disease incidence in the field. Ultimately, PF treatment led to increased peanut yield by enhancing plant numbers and pod weight compared to FO treatment, indicating its potential in mitigating Fusarium oxysporum-induced root rot disease under continuous cropping systems.

Physiological, metabolome, and transcriptome analysis revealed the effect of ethyl 3-amino-3-thioxopropanoate on the browning of fresh-cut banana during storage

The quality of fresh-cut bananas is often affected by surface browning, which does not meet consumer expectations. The ethyl 3-amino-3-thioxopropanoate (EAT) is an ethyl ester organic compound screened from Maillard reaction products that may have browning inhibition effects. However, there is still a lack of research on the practical application of EAT. This study investigated the impact of exogenous EAT on the browning process and the underlying mechanisms in fresh-cut banana through a comprehensive analysis involving physiological, metabolomic, and transcriptomic approaches. Treatment with EAT effectively mitigated the discoloration of the cut surface of slices and decreased the browning index by 74 % at the end of storage. Additionally, EAT application significantly reduced polyphenol oxidase activity, increased phenylalanine ammonia-lyase activity and total phenolic content, inhibited lipoxygenase activity, decreased malondialdehyde accumulation, enhanced antioxidant enzyme activity, and improved DPPH free radical scavenging rate to 68.49 %. Moreover, 839 metabolites were identified through non-targeted metabolomics analysis. Metabolomic and transcriptomic analysis further highlighted the importance of lipid metabolism, amino acid metabolism and secondary metabolites in influencing the sensitivity to post-cutting browning. EAT treatment also influenced the expression levels of key genes related to browning. Thus, it could be speculated that the mechanism by which EAT produces its anti-browning effect may be by reducing phenolase activity, improving levels of phenols and amino acids, enhancing the antioxidant capacity of the fruit, and alleviating membrane lipid peroxidation. In summary, this study provides valuable insights into the response mechanism employed by exogenous EAT to inhibit browning in freshly cut bananas. However, the application security and mass production methods of EAT still need further clarification.

Inoculation of Paraburkholderia sp. GD17 improves seedling growth and tolerance to Cadmium in Chinese cabbage

This study provided evidence at the first time showing that root inoculation with the plant growth-promoting rhizobacteria Paraburkholderia sp. GD17 improved the growth and tolerance to Cd stress in Chinese cabbage seedlings. Under normal conditions, the shoot fresh and dry weight of GD17-inoculated 30-day-old plants increased by about 29 % and 33 %, and their root fresh and dry weight by 104 % and 67 %, respectively, compared with their non-inoculated partners. The GD17-mediated growth promotion could be attributed to its facilitating influence on plant acquisition of nutrient elements and photosynthetic efficiency, and decreasing abscisic acid production. Under Cd stress, an effective alleviation in Cd-induced growth inhibition was observed in GD17 plants relative to non-inoculated control, suggesting that the root inoculation with GD17 played a systemic protective role. The Cd concentration in plant aerial tissues was comparable between GD17 plants and non-inoculated ones, but it was substantially decreased in GD17 plant roots. In response to Cd, GD17-inoculated plants generally showed a stronger ability to absorb and transport nutrient elements to shoots. The GD17-conferred plant tolerance to Cd was also associated with an increased antioxidative capacity companied by declined oxidative damage, optimal levels of phytohormones, increased flavonoid synthesis as indicated by significantly upregulated expression of related genes and activity of phenylalanine ammonia-lyase. Additionally, root inoculation with GD17 effectively mitigated the Cd-induced decline in photosynthetic efficiency. Collectively, this study firstly showed that GD17-conferred growth-promotion and Cd-tolerance in Chinese cabbage was correlated with multiple regulatory roles in plant metabolism, which, in most cases, was involved in the regulation at the transcription levels of relevant genes.

Preharvest methyl jasmonate application delays cell wall degradation and upregulates phenolic metabolism and antioxidant activities in cold stored raspberries

The effects of preharvest methyl jasmonate (MeJA) spray application on the physicochemical quality, metabolism of phenolics, and cell wall components in raspberries were investigated during a 10-day cold storage period. MeJA spray reduced firmness loss, decay incidence, and weight loss, while maintained higher levels of soluble solids content, ascorbic acid, anthocyanins and flavonoids in raspberries. Furthermore, MeJA application resulted in increased total pectin and protopectin levels, as well as lowered water-soluble pectin, and activities of pectin methyl esterase, polygalacturonase and cellulase enzymes. Additionally, MeJA treatment upregulated the phenylpropanoid pathway, leading to higher endogenous phenolics and activities of phenylalanine-ammonia lyase and shikimate dehydrogenase. In conclusion, preharvest MeJA spray application could be adopted to enhance the storage potential of cold-stored raspberries for 10 days by maintaining higher firmness, assuring better physicochemical quality, and increasing phenolic metabolism, while reducing cell wall hydrolysis.

Carbon Dots-Mediated Photodynamic Treatment Reduces Postharvest Senescence and Decay of Grapes by Regulating the Antioxidant System.

Grapes are susceptible to mold and decay during postharvest storage, and developing new technologies to extend their storage period has important application value. Photodynamic technology (PDT) in concurrence with carbon dots (CDs) proposes an innovative and eco-friendly preservation strategy. We examined the effects of carbon dots combined with photodynamic treatment on postharvest senescence and antioxidant system of table grape. The compounding of photodynamic technology with a 0.06 g L-1 CDs solution could possibly extend the postharvest storage period of grape berries. Through this strategy, we achieved a decreased rate of fruit rotting and weight loss alongside the delayed deterioration of fruit firmness, soluble solids, and titratable acid. As paired with photodynamic technology, CDs considerably decreased the postharvest storage loss of phenols, flavonoids, and reducing sugars as compared to the control group. Concurrently, it remarkably postponed the build-up of hydrogen peroxide (H2O2), superoxide anion (O2∙-), and malondialdehyde (MDA); elevated the levels of reduced ascorbic acid (AsA) and reduced glutathione (GSH); lowered the levels of dehydroascorbic acid (DHA) and oxidized glutathione (GSSG); raised the ratios of AsA/DHA and GSSH/GSSG; encouraged the activities of superoxide dismutase (SOD) and phenylalanine ammonia-lyase (PAL); and inhibited the activities of polyphenol oxidase (PPO) and lipoxygenase (LOX). Furthermore, it enhanced the iron reduction antioxidant capacity (FRAP) and DPPH radical scavenging capacity of grape berries. CDs combined with photodynamic treatment could efficiently lessen postharvest senescence and decay of grape berry while extending the storage time.

Anti-browning action of melatonin is dependent on the type of tissue in minimally processed sweet potatoes

This study explored the impact of exogenous melatonin on oxidative damage, protective mechanisms against oxidation, and reactions leading to browning, as well as the accumulation of antioxidants in minimally processed white-fleshed and orange sweet potato roots. Sweet potato roots with white and orange pulp were subjected to minimal processing and immersion in melatonin solutions at concentrations of 0, 10, 100, and 1000 µmol L−1. Following packaging, these were stored at 5 ± 2 °C for 20 days. Results indicate that increasing melatonin concentrations significantly reduced browning symptoms in both white and orange sweet potato slices. This reduction was associated with decreased levels of hydrogen peroxide (H2O2), thiobarbituric acid-reactive substances (TBARs), and electrolyte leakage, indicating reduced cell membrane damage. Enhanced protection was observed through increased activity of antioxidant enzymes superoxide dismutase, catalase, and ascorbate peroxidase and higher levels of antioxidant metabolites, including vitamin C and phenolic compounds, as confirmed by in vitro assays for antioxidant capacity (FRAP and DPPH), however, the levels of total carotenoids, anthocyanins, and yellow flavonoids did not show a significant difference between the melatonin treatments. Notably, sweet potato slices treated with higher melatonin doses of 100 and 1000 µmol L−1 exhibited reduced phenylalanine ammonia-lyase activity and phenolic compound accumulation. This effect, coupled with lower polyphenol oxidase (PPO) and peroxidase (POD) activities, likely contributed to prolonged preservation quality by maintaining cellular redox homeostasis.

Exogenous inoculation of Pediococcus pentosaceus SSC12 positively regulates anthocyanin biosynthesis to alleviate browning of postharvest litchi (Litchi chinensis Sonn.)

Litchi is prone to pericarp browning after-harvest, which seriously affects the quality of litchi and causes huge loss. Pericarp browning is closely related to anthocyanin metabolism. Lactic acid bacteria (LAB), a kind of probiotics, is used for food preservation. The aim of this study was to investigate whether and how inoculation of LAB strain Pediococcus pentosaceus SSC12 of litchi fruit affect the pericarp browning and anthocyanin metabolism in postharvest through transcriptome and metabolome analyses. This is the first work showing that strain SSC12 suppressed development of browning and maintained the coloration of litchi pericarp at 10 ± 1 °C. Strain SSC12 upregulated 8 key differentially expressed genes (DEGs) associated with anthocyanin biosynthesis and transport, while downregulated 3 key DEGs involved in anthocyanin degradation in anthocyanin synthesis pathway. Strain SSC12 caused increase in 9 different anthocyanin-related metabolites levels and phenylalanine ammonia lyase activity, disease in peroxidase, laccase and polyphenol oxidase activities. Taken together, strain SSC12 suppressed browning of litchi via elevateing anthocyanin synthesis and transport and inhibiting anthocyanin degradation. These findings suggested that strain SSC12 might serve as a potential probiotic strains to alternative for chemical reagents in postharvest fruit preservation and contribute to the exploration of newgreen approachs for postharvest losses.