Pre- or Post-Harvest Treatment with MeJA Improves Post-Harvest Storage of Lemon Fruit by Stimulating the Antioxidant System and Alleviating Chilling Injury

Mitigating effects of Methyl Jasmonate on photosynthetic inhibition and oxidative stress of pepper (Capsicum annuum L) seedlings under low temperature combined with low light

Low temperature combined with low light (LL) is a critical abiotic stress that restricting plant growth and yield of pepper (Capsicum annuum L.). Methyl jasmonate (MeJA) is considered with potential benefits for improving plant stress resistance; however, the physiological mechanisms underlying the adaptation of pepper to LL stress have not been explored. This study aimed to investigate the potential mitigating effects of foliar MeJA (200 μmol L-1) application on pepper seedlings subjected to LL stress (10/5 °C, 100 μmol m-2 s-1) for 168 h. Our results indicated that the application of exogenous MeJA reduced the negative effect on growth inhibition of pepper seedlings caused by LL stress, significantly increased chlorophyll contents and photosynthetic capacity as a result of improved photosynthesis rate. In addition, MeJA reduced the accumulation of reactive oxygen species and malondialdehyde contents induced by LL stress, while enhancing the activities of superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, dehydroascorbate reductase, and monodehydroascorbate reductase as a result of upregulated expression levels of antioxidant enzyme genes (CaSOD, CaPOD, CaCAT, CaAPX, CaGR, CaDHAR, and CaMDHAR). Additionally, it increased the ascorbic acid and reduced glutathione content, while reducing oxidized glutathione content, thereby preventing membrane lipid peroxidation and protecting plants from oxidative damage under LL stress. Furthermore, seedlings treated with MeJA exhibited significantly enhanced soluble sugar and soluble protein contents in leaves. Taken together, present findings indicate that MeJA application may serve as an effective strategy for mitigating LL-induced oxidative stress by maintaining plant growth, enhancing chlorophyll fluorescence, upregulating the antioxidant defence system, optimizing ascorbate-glutathione cycle, and osmotic adjustment.

Influence of ZnSO4 and Methyl Jasmonate on the Metabolites and Bioactivity Present in Lemon-Fruit Membrane Vesicles

Membrane vesicles isolated from vegetable tissues have shown promise in encapsulation technologies used in industries like food and cosmetics, offering innovative approaches to product development. However, their associated linked metabolites have not been studied. Lemon vesicle research not only adds value to the lemon crop (Citrus × limon L.), one of the most widely cultivated fruit trees in the world, is a source of bioactive compounds such as phenolics and organic acids. In this study, the influence of elicitation with ZnSO4 and methyl jasmonate, which modulate the bioactive metabolites, on fruit membrane vesicle bond metabolites was studied. The study showed that foliar application of ZnSO4 increased phenolic compounds as caffeic, sinapic, and chlorogenic acids and the flavonoid hesperidin by about 20% in lemons. Furthermore, a clear interaction between vesicles and citrate and ascorbate that were increased by methyl jasmonate were associated with their higher bioactivity. This was related to the double intrinsic in vitro antioxidant activities of these vesicles.

Melatonin Rinsing Treatment Associated with Storage in a Controlled Atmosphere Improves the Antioxidant Capacity and Overall Quality of Lemons

Antioxidant capacity is one of the most important biological activities in fruits and vegetables and is closely related to human health. In this study, 'Eureka' lemons were used as experimental materials and stored at 7-8 °C MT (melatonin, 200 μmol, soaked for 15 min) and CA (controlled atmosphere, 2-3% O2 + 15-16% CO2) individually or in combination for 30 d. The changes in lemon fruits' basic physicochemical properties, enzyme activities, and antioxidant capacities were studied. Comparing the combined treatment to the control, the outcomes demonstrated a significant reduction in weight loss, firmness, stomatal opening, and inhibition of polyphenol oxidase (PPO) and peroxidase (POD) activities. Additionally, the combined treatment maintained high levels of titratable acidity (TA), vitamin C (VC), total phenolic content (TPC), and antioxidant capacity and preserved the lemon aroma. Meanwhile, the correlation between fruit color, aroma compounds, and antioxidant capacity was revealed, providing valuable insights into the postharvest preservation of lemons. In conclusion, the combined treatment (MT + CA) was effective in maintaining the quality and antioxidant capacity of lemons.

Enhancing Mexican lime (Citrus aurantifolia cv.) shelf life with innovative edible coatings: xanthan gum edible coating enriched with Spirulina platensis and pomegranate seed oils

BACKGROUND

The Mexican lime (Citrus aurantifolia cv.), widely consumed in Iran and globally, is known for its high perishability. Edible coatings have emerged as a popular method to extend the shelf life of fruits, with xanthan gum-based coatings being particularly favored for their environmental benefits. This study aims to evaluate the effectiveness of an edible coating formulated from xanthan gum, enriched with Spirulina platensis (Sp) and pomegranate seed oil (PSO), in improving the quality and reducing the weight loss of Mexican lime fruit under conditions of 20 ± 2 °C and 50-60% relative humidity.

RESULTS

Based on the results, the application of coatings was generally effective in reducing fruit weight loss, with the least weight loss observed in the xanthan gum 0.2%+ Spirulina platensis extract (1%) treatment. Additionally, the levels of total phenols and flavonoids in the treated fruits exceeded those in the control group, with xanthan gum 0.2%+ Spirulina platensis extract (1%) and xanthan gum 0.2% exhibiting the highest concentrations of these compounds. The antioxidant capacity of the fruits was also enhanced by the coatings, surpassing that of the control group, with xanthan gum 0.2%+ Spirulina platensis extract (1%) achieving the highest levels. The treatments significantly suppressed the activity of the polyphenol oxidase (PPO) enzyme, with xanthan gum 0.2% demonstrating the most potent inhibitory effect. Furthermore, the treatments resulted in increased activities of catalase (CAT) and peroxidase (POD) enzymes compared to the control. Except for xanthan gum 0.2%+ pomegranate seed oil (0.05%), all treatments maintained the fruit's greenness (a*) more effectively than the control.

CONCLUSIONS

Peel browning is a major factor contributing to the decline in quality and shelf life of lime fruit. The application of 0.1% and 0.2% xanthan gum coatings, as well as a combination of 0.2% xanthan gum and Spirulina platensis extract, significantly inhibited PPO activity and enhanced the activity of CAT and POD and phenolic compound in Mexican lime fruits stored at of 20 ± 2 °C for 24 days. Consequently, these treatments comprehensively preserved lime fruit quality by significantly reducing browning, maintaining green color, and preserving internal quality parameters such as TA, thereby enhancing both visual appeal and overall fruit quality.

Endogenous Hormone Levels and Transcriptomic Analysis Reveal the Mechanisms of Bulbil Initiation in Pinellia ternata

Pinellia ternata is a medicinal plant that has important pharmacological value, and the bulbils serve as the primary reproductive organ; however, the mechanisms underlying bulbil initiation remain unclear. Here, we characterized bulbil development via histological, transcriptomic, and targeted metabolomic analyses to unearth the intricate relationship between hormones, genes, and bulbil development. The results show that the bulbils initiate growth from the leaf axillary meristem (AM). In this stage, jasmonic acid (JA), abscisic acid (ABA), isopentenyl adenosine (IPA), and salicylic acid (SA) were highly enriched, while indole-3-acetic acid (IAA), zeatin, methyl jasmonate (MeJA), and 5-dexoxystrigol (5-DS) were notably decreased. Through OPLS-DA analysis, SA has emerged as the most crucial factor in initiating and positively regulating bulbil formation. Furthermore, a strong association between IPA and SA was observed during bulbil initiation. The transcriptional changes in IPT (Isopentenyltransferase), CRE1 (Cytokinin Response 1), A-ARR (Type-A Arabidopsis Response Regulator), B-ARR (Type-B Arabidopsis Response Regulator), AUX1 (Auxin Resistant 1), ARF (Auxin Response Factor), AUX/IAA (Auxin/Indole-3-acetic acid), GH3 (Gretchen Hagen 3), SAUR (Small Auxin Up RNA), GA2ox (Gibberellin 2-oxidase), GA20ox (Gibberellin 20-oxidase), AOS (Allene oxide synthase), AOC (Allene oxide cyclase), OPR (Oxophytodienoate Reductase), JMT (JA carboxy l Methyltransferase), COI1 (Coronatine Insensitive 1), JAZ (Jasmonate ZIM-domain), MYC2 (Myelocytomatosis 2), D27 (DWARF27), SMAX (Suppressor of MAX2), PAL (Phenylalanine Ammonia-Lyase), ICS (Isochorismate Synthase), NPR1 (Non-expressor of Pathogenesis-related Genes1), TGA (TGACG Sequence-specific Binding), PR-1 (Pathogenesis-related), MCSU (Molybdenium Cofactor Sulfurase), PP2C (Protein Phosphatase 2C), and SnRK (Sucrose Non-fermenting-related Protein Kinase 2) were highly correlated with hormone concentrations, indicating that bulbil initiation is coordinately controlled by multiple phytohormones. Notably, eight TFs (transcription factors) that regulate AM initiation have been identified as pivotal regulators of bulbil formation. Among these, WUS (WUSCHEL), CLV (CLAVATA), ATH1 (Arabidopsis Thaliana Homeobox Gene 1), and RAX (Regulator of Axillary meristems) have been observed to exhibit elevated expression levels. Conversely, LEAFY demonstrated contrasting expression patterns. The intricate expression profiles of these TFs are closely associated with the upregulated expression of KNOX(KNOTTED-like homeobox), suggesting a intricate regulatory network underlying the complex process of bulbil initiation. This study offers a profound understanding of the bulbil initiation process and could potentially aid in refining molecular breeding techniques specific to P. ternata.

Advances in the Understanding of Postharvest Physiological Changes and the Storage and Preservation of Pitaya

Highly prized for its unique taste and appearance, pitaya is a tasty, low-calorie fruit. It has a high-water content, a high metabolism, and a high susceptibility to pathogens, resulting in an irreversible process of tissue degeneration or quality degradation and eventual loss of commercial value, leading to economic loss. High quality fruits are a key guarantee for the healthy development of economic advantages. However, the understanding of postharvest conservation technology and the regulation of maturation, and senescence of pitaya are lacking. To better understand the means of postharvest storage of pitaya, extend the shelf life of pitaya fruit and prospect the postharvest storage technology, this paper analyzes and compares the postharvest quality changes of pitaya fruit, preservation technology, and senescence regulation mechanisms. This study provides research directions for the development of postharvest storage and preservation technology.

Application of Methyl Jasmonate to Papaya Fruit Stored at Lower Temperature Attenuates Chilling Injury and Enhances the Antioxidant System to Maintain Quality

Papaya fruit has a limited shelf life due to its sensitivity to decay and chilling damage during cold storage. The application of methyl jasmonate (MeJA) is known to reduce the incidence of disease and chilling injury, and to maintain the overall quality of the papaya fruit when stored at low temperature. Consequently, the effects of postharvest MeJA (1 mM) immersion on papaya fruits during low-temperature storage (10 °C ± 2 °C) for 28 days were studied. The experiment revealed that MeJA treatment significantly decreased the papaya fruit's weight loss, disease incidence, and chilling injury index. Furthermore, the accumulation of malondialdehyde and hydrogen peroxide was markedly lower after the application of MeJA. In addition, MeJA treatment exhibited significantly higher total phenols, ascorbic acid, antioxidant activity, and titratable acidity in contrast to the control. Similarly, MeJA-treated papaya fruits showed higher antioxidant enzymatic activity (superoxide dismutase, catalase, and peroxidase enzymes) with respect to the control fruits. In addition, MeJA reduced the soluble solids content, ripening index, pH, and sugar contents compared to the control fruits. Furthermore, MeJA-treated papaya fruit exhibited higher sensory and organoleptic quality attributes with respect to untreated papaya fruits. These findings suggested that postharvest MeJA application might be a useful approach for attenuating disease incidence and preventing chilling injury by enhancing antioxidant activities along with enhanced overall quality of papaya fruits during low-temperature storage.

Methyl jasmonate treatment alleviates chilling injury and improves antioxidant system of okra pod during cold storage

Okra pod is sensitive to low temperature, which results in chilling injury under improper low-temperature storage. This study aimed to evaluate the effect of different concentrations of methyl jasmonate (MeJA) treatment on okra pod stored at 4 ± 1°C for 12 days and illuminate the mechanism of MeJA alleviating chilling injury. Compared to the control, MeJA treatments maintained lower relative electric conductivity (REC), chilling injury (CI) degree, and lignin content, as well as higher total soluble solids, total soluble sugar, pectin content, and chlorophyll content. The factor analysis was applied to comprehensively evaluate the effects of MeJA so that 1 μmol/L MeJA was screened as the optimum concentration to maintain the okra quality throughout the storage time. In contrast with control, MeJA not only accelerated the generation of antioxidant substances (phenolics and flavonoids) but also increased the superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD) activity, inhibited malondialdehyde (MDA), hydrogen peroxide (H2O2) content accumulation, and the polyphenol oxidase (PPO) activity. This work confirmed that MeJA could effectively alleviate chilling injury and maintain the quality during cold-stored by regulating reactive oxygen species (ROS) metabolism. These results provide theoretical guidance for the application of MeJA in okra storage and preservation.

Comprehensive analysis of MAPK gene family in Populus trichocarpa and physiological characterization of PtMAPK3-1 in response to MeJA induction

Mitogen-activated protein kinases (MAPKs) play important roles in plant growth and development, as well as hormone and stress responses by signaling to eukaryotic cells, through MAPK cascade, the presence of various cues; thereby, regulating various responses. The MAPK cascade consists mainly of three gene families, MAPK, MAPKK, and MAPKKK, which activate downstream signaling pathways through sequential phosphorylation. Although the MAPK cascade gene family has been reported in several species, there is a lack of comprehensive analysis in poplar. We identified 21 MAPK genes, 11 MAPKK genes, and 104 MAPKKK genes in Populus trichocarpa. The phylogenetic classification was supported by conservative motif, gene structure and motif analysis. Whole genome duplication has an important role in the expansion of MAPK cascade genes. Analysis of promoter cis-elements and expression profiles indicates that MAPK cascade genes have important roles in plant growth and development, abiotic and biotic stresses, and phytohormone response. Expression profiling revealed a significant upregulation of PtMAPK3-1 expression in response to drought, salt and disease stresses. Poplar transiently overexpressing PtMAPK3-1 and treated with methyl jasmonic acid (MeJA) had higher catalase and peroxidase levels than non-overexpressing poplar. This work represents the first complete inventory of the MAPK cascade in P. trichocarpa, which reveals that PtMAPK3-1 is induced by the MeJA hormone and participates in the MeJA-induced enhancement of the antioxidant enzyme system.