Phenylalanine Ammonia-lyase Activity Research Articles

Biocontrol of Fusarium solani: Antifungal Activity of Chitosan and Induction of Defence Enzymes

In this work, the efficiency of chitosan as a biocontrol agent against Fusarium solani on tomato plants was determined and the antifungal activity and the induction of defence enzymes were evaluated. Treatments were carried out with different concentrations of chitosan (1, 2 and 3 g L−1) combined with a synthetic fungicide (carbendazim). The results showed that all chitosan treatments significantly inhibited the mycelial growth and biomass of F. solani, with the most effective results obtained with the 3 g L−1 treatment. Scanning electron microscopy revealed that chitosan causes severe structural damage to F. solani, including cell lysis and the deformation of mycelium and spores. In addition, plants treated with chitosan showed significant improvements in height, stem diameter, root dry biomass and root length compared to those treated with synthetic fungicide and the control (no chitosan application). Enzyme assays showed that chitosan significantly increased superoxide dismutase, catalase, peroxidase and phenylalanine ammonia-lyase activity, indicating an increased defensive response. These results suggest that chitosan is a viable and less toxic alternative for the management of disease caused by F. solani in tomato plants, promoting both plant health and growth.

The impact of fruit size on internal browning in pineapples.

A typical symptom of post-harvest pineapple (Ananas comosus L.) internal browning is influenced by multiple factors. However, the precise mechanism through which fruit size influences the occurrence of browning remains unclear. Therefore, this study aimed to investigate the impacts of fruit size in browning and its possible mechanisms in harvested pineapple fruit using physical and biochemical analysis and RNA-seq. Disease incidence was assessed in four groups of fruits (1, 1.5, 2, and 2.5±0.2kg), with the two most significant groups (1 and 2.5±0.2kg) selected for detailed analysis. The results showed that the large pineapple fruits had faster browning senescence and membrane lipid peroxidation, higher respiration intensity, more reactive oxygen speciesaccumulation, and higher malondialdehydecontent. Likewise, lower antioxidant capacity such as ascorbic acid, ascorbate peroxidase, catalase, and superoxide dismutase and higher polyphenol oxidase activity, peroxidase activity, phenylalanine ammonia-lyaseactivity, and lipoxygenaseactivity. It can be concluded that the large pineapple fruits were severely subjected to oxygen stress and membrane lipid peroxidation during storage. Gene ontology enrichment reveals that this relates mainly to oxidoreductase and glutathione metabolism. The large pineapple fruits accelerated AsA-GSH cycle pathway metabolism. Real-time quantitative PCRshows downregulated expression of AcAPX1, AcAPX6, AcAPX6×1, AcCAT2, AcSOD[Fe]2, and AcSODX2 in large pineapple fruits, whereas AcPPO and AcLOX upregulated expression. This study offers insights into fruit size and browning. Future molecular techniques may reduce fruit browning.

Mechanisms Involved in Cell Wall Remodeling in Etiolated Rice Shoots Grown Under Osmotic Stress

Osmotic stress impacts the cell wall properties in plants. This study aimed to elucidate the mechanisms involved in cell wall remodeling in etiolated (dark-grown) rice (Oryza sativa L.) shoots grown under polyethylene glycol (PEG)-induced osmotic stress conditions. Shoot growth was inhibited by 70% by the treatment with 60 mM PEG for 2 days. However, when the stressed seedlings were transferred to a solution without PEG, their shoot growth rate increased significantly. A measurement of the cell wall mechanical properties revealed that the cell walls of the stressed shoots became looser and more extensible than those of unstressed shoots. Among the cell wall constituents, the amounts of cellwall-bound phenolic acids, such as ferulic acid (FA), p-coumaric acid (p-CA), and diferulic acid (DFA), per shoot and per unit of matrix polysaccharide content were significantly reduced in the stressed shoots compared to those in the unstressed shoots. Concerning the formation of cellwall-bound phenolic acids, the activity of cellwall-bound peroxidase (CW-PRX) per unit of cell wall content, which is responsible for the coupling reaction of FA to produce DFA, was 3.5 times higher in stressed shoots than in unstressed shoots, while the activity was reduced by 20% on a shoot basis in stressed shoots compared to that in unstressed shoots. The expression levels of the major class III peroxidase genes in stressed shoots were either comparable to or slightly lower than those in unstressed shoots. Conversely, the phenylalanine ammonia-lyase (PAL) activity, which contributes to the biosynthesis of FA and p-CA, was reduced by 55% and 30% on a shoot and unit-of-protein-content basis, respectively, in stressed shoots compared to that in unstressed shoots. The expression levels of abundantly expressed PAL genes decreased by 14–46% under osmotic stress. Moreover, the gene expression levels of specific BAHD acyltransferases, which are responsible for the addition of FA and p-CA to form ester-linked moieties on cell wall constituents, decreased by 15–33% under osmotic stress. These results suggest that the downregulation of the expression of specific PAL and BAHD acyltransferase genes in osmotically stressed rice shoots is responsible for a reduction in the formation of cellwall-bound phenolic acid monomers. This, in turn, may result in a decrease in the levels of DFAs. The reduction in the formation of DFA-mediated cross-linking structures within the cell wall may contribute to an increase in the mechanical extensibility of the cell wall. The remodeling of cell walls in an extensible and loosened state could assist in maintaining the growth capacity of etiolated rice shoots grown under osmotic stress and contribute to rapid growth recovery following the alleviation of osmotic stress.

Systemic Acquired Resistance: Plant Priming for Ecological Management of Mealybug-Induced Wilt in MD2 and Queen Victoria Pineapples

Pineapples are highly susceptible to “Wilt disease”, caused by the biotrophic insect Dysmicoccus brevipes that also transmits several Wilt-associated viruses (PMWaVs). Conventional farms manage mealybugs and Wilt disease using chemicals. However, many of these chemicals have been banned in Europe due to safety concerns, leading to a critical need for studies on pesticide-free control methods. During their evolution, plants have developed natural defences, such as systemic acquired resistance (SAR), against pathogens and pests. In this study, salicylic acid (10−3 M) was applied to MD2 and Queen Victoria pineapple plants as a foliar spray or soil drench, followed by mealybug infestation. This treatment enhanced defences, assessed through mealybug multiplication rates, and biochemical and molecular responses of tissue-cultured plantlets under controlled conditions. Phenylalanine ammonia-lyase activity (PAL) was measured as a potential SAR signalling enzymatic marker. Additionally, the expression levels of four genes were analyzed, which included AcPAL and AcICS2, both linked to salicylic acid synthesis; AcMYB-like, a transcription factor regulating salicylic acid biosynthesis; and AcCAT, which is involved in H2O2 level control in plants. SA elicitation reduced the mealybug multiplication rate by 70% on pineapples compared to untreated plants. In this study, the biochemical marker (PAL) and three molecular markers (AcPAL, AcICS2, and AcCAT) showed significant differences between primed and unprimed plants, indicating SAR induction and its role in the pineapple–mealybug interaction. In MD2 and Queen Victoria, PAL increased by 2.3 and 1.5, respectively, while AcPAL increased by 4 and more than 10. The other molecular markers, AcICS2, AcCAT, and AcMYB-like (a transcription factor), increased by 3, except for the last one in Queen Victoria. The reduction in mealybug populations with SAR is less effective than with pesticides, but it provides a valuable alternative on Réunion Island, where the only remaining insecticide will soon be banned. In addition, SAR priming offers a promising, eco-friendly strategy for managing mealybug populations and reducing Wilt disease in pesticide-free pineapple cropping systems.

Alginate oligosaccharide induces resistance against Penicillium expansum in pears by priming defense responses.

The research intended to explore the control ability of alginate oligosaccharide (AOS) on Penicillium expansum infection in pear fruit by priming response and its mechanism. The results showed that 100mgL-1 AOS treatment could significantly reduce the incidence of postharvest blue mold and the lesion diameter in pear fruits and maintain their quality. The defense responses induced by AOS treatment alone were relatively mild in pear fruits. Still, AOS-treated pear fruits inoculated with P. expansum showed more intense disease resistance responses. These defense responses included enhanced activities of chitinase (CHI), β-1, 3-glucanase (GLU), peroxidase (POD), polyphenol oxidase (PPO), phenylalanine ammonia-lyase activity (PAL), along with the accumulation of total phenolic compounds, flavonoids and lignin. Additionally, the expression levels of defense-related genes, such as PbGLU, PbCHI, PbPAL, PbPOD and PbPPO, were significantly upregulated. However, AOS did not show a potential inhibitory effect on the in vitro growth of P. expansum. Our results indicated that AOS treatment in the postharvest pear fruit enhances disease resistance by priming its defense responses.

Relevance of plant growth-promoting bacteria in reducing the severity of tomato wilt caused by Fusarium oxysporum f. sp. lycopersici by altering metabolites and related genes.

Among the biotic stresses, wilt disease severely affects tomato quality and productivity globally. The causal organism of this disease is Fusarium oxysporum f. sp. lycopersici (Fol), which is very well known and has a significant impact on the productivity of other crops as well. Efforts have been made to investigate the effect of plant growth-promoting bacteria (PGPB) on alleviating tomato wilt disease. Four PGPB strains, such as Pseudomonas aeruginosa BHUPSB01 (T1), Pseudomonas putida BHUPSB04 (T2), Paenibacillus polymyxa BHUPSB16 (T3), and Bacillus cereus IESDJP-V4 (T4), were used as inocula to treat Fol-challenged plants. The results revealed that PGPB treatments T1, T2, T3, and T4 were able to decrease the severity of Fusarium wilt in the tomato plants at different levels. Among the treatments, T3 displayed the strongest protective effect, with the lowest disease frequency, which was 15.25%. There were no significant differences observed in parameters such as fruit yield and relative water content in the PGPB-inoculated plants, although T3 and T4 showed minimal electrolyte leakage. Significant changes in chlorophyll fluorescence were also recorded. A lower level of H2O2 and malondialdehyde (MDA) was observed in the T3 and T4 treatments. In addition, proline accumulation was highest in the T3-treated plants. Antioxidative enzyme activities, such as catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), significantly increased in the PGPB-treated plants. Furthermore, the highest phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO) activity was reported in the T3 and T4 plants, respectively. The PGPB-treated plants showed elevated expression of the PAL, PPO, PR3, PR2, SOD, CAT, and PO genes. This study's results reveal that PGPB strains can be utilized as biocontrol agents (BCAs) to enhance tomato resistance against Fusarium wilt.

Production of neuroprotective compounds from barley (Hordeum vulgare L.) germinated under different conditions during the malting process

Abstract The effect of different barley germination conditions on generation of neuroprotective compounds was studied. Malts were obtained by germination at 20 °C for 35 hr (M1), 20 °C for 72 hr (M2), 25 °C for 35 hr (M3), and 25 °C for 72 hr (M4). M4 showed higher phenylalanine ammonia lyase (PAL) activity and total phenolic acid content than the others. Moreover, a direct relationship (r2: 0.9802) between protein hydrolysis degree and malt protease activity was obtained. Regarding neuroprotective properties, all malts inhibited the acetylcholinesterase, tyrosinase, and prolyl oligopeptidase enzymes. However, M4 showed the highest inhibitory activity. This effect was due to the higher proportion of 595 and 392 Da peptides with high hydrophobicity and the higher phenolic acid content in this malt. Thus, the temperature and time of barley germination influenced the enzymatic activity of proteases and PAL, which modified the activity and profile of neuroprotective compounds in malts.

Metabolomics-based study on the effect of low-voltage electrostatic field treatment on the storage quality of postharvest square bamboo shoots.

Low-voltage electrostatic field (LP) enhances the freezing quality of food by increasing water supercooling and improving ice crystal morphology. This study explored the effects of LP treatment on the storage quality of square bamboo shoots using physicochemical, gas chromatography-mass spectrometry, and metabolomics methods. Results showed that with prolonged storage, the LP-treated group had lower activities of peroxidase, phenylalanine ammonia-lyase, and lower levels of malondialdehyde, cellulose, and lignin compared to the control group, while superoxide dismutase and catalase activities and shear force values were higher. LP treatment also increased the levels of hexanol, (E)-2-hexenal, and azelaic acid, promoted the production of 2-nonanol and (Z)-2-heptenal, and inhibited the reduction of DL-malic acid, methionine, and the increase of L-phenylalanine and 4-coumaric acid. These changes were closely related to fatty acid metabolism, TCA cycle, and phenylalanine metabolism pathways. Overall, LP treatment can effectively improve the storage quality of square bamboo shoots.

Melatonin induces resistance against Colletotrichum gloeosporioides in mango fruit via regulation of defense-related genes by MiWRKY45 transcription factor.

Anthracnose caused by Colletotrichum gloeosporioides is a major disease leading to postharvest loss of mango fruit. Melatonin (MT) is a natural bioactive molecule that has multiple physiological functions in plants. This study investigated the effect of exogenous MT on mango disease resistance against C. gloeosporioides and related molecular mechanism. MT treatment at 1 mmol L-1 limited the expansion of anthracnose in mango inoculated with C. gloeosporioides, which was associated with increased level of defense-related indexes, including activities of phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4CL) and peroxidase (POD), expression of MiPAL, Mi4CL and MiPOD and contents of total phenolics, flavonoids and lignin. RT-qPCR analysis of 15 MiWRKY members revealed that MiWRKY45 had the highest expression in response to MT + C. gloeosporioides. MiWRKY45 transcription factor was identified as a nucleus-localized transcriptional activator based on subcellular localization and transcriptional activation assays. MiWRKY45 bound to W-box motif and activated the expression of MiPAL, Mi4CL and MiPOD, as verified by DNA affinity purification-seq (DAP-seq), yeast one-hybrid (Y1H) and dual-luciferase reporter (DLR) assays. Transient transformation analysis revealed that MiWRKY45 positively regulated phenylpropanoid pathway, thereby enhancing mango resistance. These results suggest that MiWRKY45, as a positive regulator, is involved in MT-induced resistance against anthracnose in mangoes.

Histopathological and biochemical variations in resistant and susceptible black pepper cultivars infected with Meloidogyne incognita

Plant-parasitic nematodes cause yield losses ranging from 30 to 65% in black pepper. Root-knot nematodes are a bottleneck in production of black pepper in Kerala, India. Identifying resistant cultivars have gained attention, as they provide an eco-friendly alternative to chemical nematicides. This study aimed to identify a root-knot nematode-resistant black pepper cultivar and determine the biochemical and histopathological changes caused by the nematode. Twenty-six black pepper cultivars (10 KAU released, 2 wild and 14 local) were screened for nematode resistance under pot culture conditions. The local cultivar Koshinadan exhibited resistance to Meloidogyne incognita (gall index 2), while the hybrid variety Panniyur 1 showed high susceptibility (gall index 5). Analysis of the biochemical basis of resistance revealed enhanced level of phenol content and activity of peroxidase, phenylalanine ammonia-lyase, and polyphenol oxidase in leaves and roots of Koshinadan compared to susceptible cultivar, Panniyur 1. Histopathological studies of the most resistant (Koshinadan) and susceptible (Panniyur 1) cultivars revealed that giant cells formed near the vascular region at different inoculum levels (0, 100, 500, 1000, 5000, 10000 J2 pot-1). The number and size of giant cells were lower in Koshinadan compared to Panniyur 1 and complete disorganization of xylem and phloem vessels was observed in the susceptible Panniyur 1. The resistant cultivar identified can serve as rootstock for grafting high-yielding varieties, resulting in nematode free seedlings.

Fullerenol nanoparticles and AMF application for optimization of Brassica napus L. resilience to lead toxicity through physio-biochemical and antioxidative modulations

Crop plants are severely affected by heavy metals (HMs), leading to food scarcity and economical loss. Lead (Pb) is outsourced by use of lead-based fertilizers, batteries, mining, smelting and metal processing. It significantly reduces growth, development and yield of crops cultivated on contaminated sites. In this study, the ameliorative role of carbon based fullerenol nanoparticles (FNPs) in combination with Arbuscular Mycorrhizal Fungi (AMF) inoculation was examined in Brassica napus L. grown in Pb contaminated soil. A pot experiment in three-ways completely randomize fashion with three replicates was conducted. For Pb stress, a 200 µM PbCl2 solution was applied at a rate of 1 L per pot. FNPs were applied via foliar spray at a concentration of 3 mM. For AMF inoculation rhizospheric soil was collected from Sorghum bicolor fields and used in this experiment. Results of the study showed that Pb toxicity greatly reduced growth (shoot length; 15%, root length; 25%) of B. napus plants. It lowered photosynthesis (38%) and gas exchange related attributes. Pb contamination caused oxidative stress, evident from elevated level of malondialdehyde (62%), and reactive oxygen species (H2O2; 60%, OH−; 103% and O2•−; 23%). It also triggered the antioxidant defense system of B. napus. These plants also had high Pb metal ions in their root and shoot compared with control. Foliar application of FNPs along with AMF inoculation effectively mitigated oxidative stress caused by Pb via increasing antioxidant enzymes activities. Catalase, peroxidase, superoxide dismutase, ascorbate peroxidase, glutathione reductase, phenylalanine ammonia-lyase and polyphenol peroxidase activities were increased by 37, 19, 96, 200, 47, 117 and 47%, respectively. In conclusion, these treatments modulated photosynthetic machinery, antioxidant defense mechanism and nutrients uptake in B. napus plants to alleviate Pb stress. It is presumed that use of carbon-based nano particles in combination with AMF inoculation could effectively mitigate HMs stress in crop plants grown in contaminated soil.

Integrative analyses of the transcriptome and metabolome reveal comprehensive mechanisms of monolignol biosynthesis in response to bioclimatic factors in Magnolia officinalis

BackgroundMagnolia officinalis (M. officinalis) thrives in temperate, elevated regions, and its desiccated bark comprises medicinal monolignol. Both abiotic and biotic factors can influence the pharmacodynamic compounds of M. officinalis, which display a variety of capabilities. It was the goal of this study to find the main bioclimatic factors that impact the amount of helpful compounds in M. officinalis and to show how these bioclimatic factors influence the metabolic pathways of magnolol and honokiol through actions on transcripts and molecules. We assessed the amounts of medicinal compounds in M. officinalis from Baoxing (BX), Nanjiang (NJ), Xuanhan (XH), and Beichuan (BC) in Sichuan Province. After that, the bioclimatic factors were gathered and put together that affected the growth and used the transcriptome and metabolome to label the M. officinalis data. The associated metabolic pathways were analyzed based on significant alterations in bioclimatic factors.ResultsTemperature and precipitation influence the accumulation of bioactive compounds in M. officinalis, as well as the metabolism of monolignol, amino acids, flavonoids, α-linolenic acid, and arachidonic acids. Moreover, temperature was negatively related to the mounts of phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4CL), and cinnamoyl-CoA reductase (CCR) in the monolignol biosynthetic pathway, as well as to the amounts of cinnamyl alcohol and 4-coumaryl alcohol that were made.ConclusionsModerate temperatures and appropriate precipitation enhanced the metabolism of monolignols in M. officinalis, ascribed to elevated levels of effective enzyme that correlated with the temperature and precipitation modulation of PAL, 4CL, and CCR activity. Furthermore, this study discovered that cinnamonyl alcohol and 4-coumaryl alcohol were critical precursors for the production of magnolol and honokiol, indicating potential strategies for improving M. officinalis' pharmacodynamic characteristics.

Antifungal Properties of Bioactive Compounds Isolated from Fucus vesiculosus Supercritical Carbon Dioxide Extract.

The exploration of natural antifungal substances from algal origins is significant due to the increasing resistance of pathogens to conventional antifungal agents and the growing consumer demand for natural products. This manuscript represents the inaugural investigation into the antifungal attributes of bioactive compounds extracted from Fucus vesiculosus via supercritical carbon dioxide (scCO2) extraction utilizing contemporary countercurrent chromatography (CCC). In aligning with the prospective utilization of this extract within the agricultural sector, this study also serves as the preliminary report demonstrating the capability of Fucus vesiculosus scCO2 extract to enhance the activity of plant resistance enzymes. The fractions obtained through CCC were subjected to evaluation for their efficacy in inhibiting the macrospores of Fusarium culmorum. The CCC methodology facilitated the successful separation of fatty acids (reaching up to 82.0 wt.% in a given fraction) and fucosterol (attaining up to 79.4 wt.% in another fraction). All CCC fractions at the concentration of 1.0% were found to inhibit 100% of Fusarium culmorum growth. Moreover, Fucus vesiculosus scCO2 extract was able to activate plant resistance enzymes (Catalase, Ascorbic Peroxidase, Guaiacol Peroxidase, Phenylalanine Ammonia-Lyase, and Phenylalanine Ammonia-Lyase Activity).

The Induction of Disease Resistance by Scopolamine and the Application of Datura Extract Against Potato (Solanum tuberosum L.) Late Blight.

Late blight, caused by Phytophthora infestans, is a devastating disease of potato. Our previous work illustrated that scopolamine, the main bioactive substance of Datura extract, exerts direct inhibitory effects on P. infestans, but it is unclear whether scopolamine and Datura extract can boost resistance to late blight in potato. In this study, P. infestans is used to infect scopolamine-treated potato pieces and leaves, as well as whole potatoes. We found that scopolamine-treated potato is resistant to P. infestans both in vitro and in vivo. The treatment of 4.5 g/L scopolamine reduces the lesion size of whole potato to 54% compared with the control after 20 d of the infection of P. infestans. The disease-resistant substance detection based on the kit method shows that scopolamine triggers the upregulation of polyphenoloxidase, peroxidase, superoxide dismutase activities, and H2O2 contents in potato tubers, and the decline of phenylalanine ammonia lyase and catalase activity. A total of 1682 significantly differentially expressed genes were detected with or without scopolamine treatment through high-throughput transcriptome sequencing and the DESeq2 software (version 1.24.0), including 705 upregulated and 977 downregulated genes. Scopolamine may affect the genes functioning in the cell wall, membrane and the plant-pathogen interaction. The addition of Datura extract could directly inhibit the mycelial growth of P. infestans on rye plate medium. In addition, P. infestans was found to be resistant to late blight in potato pieces treated with Datura extract. Datura extract can also be utilized in combination with the chemical fungicide Infinito in field experiments to lessen late blight symptoms and enhance potato yield. To our knowledge, this is the first study to detect the induction of disease resistance by scopolamine, and it also explores the feasibility of Datura extract in potato disease resistance.

Trichoderma longibrachiatum (T6) Peptaibols Inhibiting the Monilia yunnanensis Growth and Inducing Pear Fruit Resistance in Its Infection.

Pear fruit brown rot, caused by Monilia yunnanensis, affects pear fruit yields and quality. The present study determined Trichoderma longibrachiatum T6 (T6) peptaibols as a biological control alternative to synthetic fungicides and assessed its efficacy against M. yunnanensis through dual plate culture and surface spraying at different concentrations. T6 peptaibols effectively inhibited M. yunnanensis growth, achieving an 85.99% inhibitory rate at 1250 µg/mL after inoculation on PDA medium for 5 days, and 84.57% control efficacy on pear fruit with the same concentration at 6 days. Treatment with T6 peptaibols significantly decreased the average contents of malondialdehyde (MDA) and hydrogen peroxide (H2O2), as well as electrolyte leakage, by 31.99%, 27.93%, and 21.00% from days 1 to 9 post-inoculation, respectively, in comparison to the negative control. Additionally, the average antioxidant enzyme activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD) and polyphenol oxidase (PPO) increased by 86.27%, 56.76%, 25.94%, and 47.88%, respectively; the average defense enzyme activities of phenylalanine ammonia-lyase (PAL), lipoxygenase (LOX), chitinase (CHI), and β-1,3-glucanase (β-Glu) increased by 63.00%, 55.70%, 26.19%, and 16.34%, respectively. Moreover, the expression levels of the antioxidant and defense-related genes (CAT, SOD, POD, PPO, CHI, LOX, PAL, β-Glu) were significantly upregulated by 2.80, 2.81, 3.03, 2.79, 3.37, 2.49, 2.73, and 1.83-folds at 3 days after inoculation compared to the negative control. Thus, T6 peptaibols effectively reduced the pathogen infection through growth inhibition and antioxidant defenses, thereby boosting fruit immunity.

Effects of 1-methylcyclopropene (1-MCP) and ethylene on lignification and postharvest quality of Cili (Rosa sterilis D. shi) fruit

ABSTRACT Cili (Rosa sterilis D. shi) fruit is appealing to consumers due to its sensorial and nutritional characteristics. However, postharvest lignification leads to the loss of acceptance and edible quality of the fruit. In this study, the effects of postharvest treatment with 1.0 μL L−1 1-methylcyclopropene (1-MCP) and 100 μL L−1 ethylene on lignification and the postharvest quality of Cili fruit were investigated by analysing lignin metabolism, sucrose metabolism, and cell wall enzyme activities. The results showed that ethylene facilitated an increase in the respiration rate and weight loss of the fruit, promoted the activities of cell wall-related enzymes, including cellulase, sucrose synthase, β-galactosidase, phenylalanine ammonialyase and peroxidase, and accelerated the accumulation of total polyphenols and lignin. By contrast, 1-MCP had the opposite effects. Together, these findings show that 1-MCP can maintain the quality of Cili fruit by inhibiting lignification, while ethylene may play an important role in the lignification process.

Unraveling Quinoa (Chenopodium quinoa Willd.) Defense Against Downy Mildew (Peronospora variabilis): Comparative Molecular Analysis of Resistant "Hualhuas" and Susceptible "Real" Cultivars.

Quinoa (Chenopodium quinoa Willd.) is a new, promising non-conventional useful crop; however, its susceptibility to downy mildew, caused by Peronospora variabilis, is a key obstacle limiting its productivity in Egypt. Identifying and utilizing resistant quinoa cultivars appear to be reliable and cost-efficient strategies for controlling downy mildew, particularly in resource-limited farmers' fields. This study aimed to evaluate the differential resistance of the Peruvian "Hualhuas" and Bolivian "Real" quinoa cultivars to P. variabilis infection under laboratory conditions to provide precise insight into their basic defense mechanism(s). Inoculated "Hualhuas" plants displayed complete resistance against P. variabilis, with no visible symptoms (incompatible reaction), while those of "Real" plants revealed high susceptibility (compatible reaction), with typical downy mildew lesions on their leaf surfaces. Disease incidence reached about 66% in the inoculated "Real" plants, with most inoculated leaves having lesions of grades 4 and 5 covering up to 90% of their leaf surfaces. Susceptibility indices reached up to 66% in the inoculated "Real" plants. Resistance to P. variabilis observed in the "Hualhuas" plants may have been largely attributed to elevated endogenous H2O2 levels, increased peroxidase (POX) activity and abundance, enhanced phenylalanine ammonia-lyase (PAL) activity and expression, as well as the upregulation of the pathogen-related protein 10 gene (PR-10). The results of this study indicate that the quinoa cultivar "Hualhuas" not only is a promising candidate for sustainable control of quinoa downy mildew but also, through a deep understanding of its molecular resistance mechanisms, would provide a possible route to enhance downy mildew resistance in other genotypes.

BcVQ11A-BcWRKY23-BcWRKY25 Module Is Involved in Thermotolerance by Regulating Phenylalanine Ammonia-Lyase Activity in Non-Heading Chinese Cabbage.

High temperature can significantly affect the quality and yield of plants. However, there has been limited research investigating the thermotolerance of non-heading Chinese cabbage (NHCC). This study, identified BcWRKY23 through transcriptome analysis in NHCC with varying levels of thermotolerance. Overexpression and silencing experiments demonstrated that BcWRKY23 positively regulates the thermotolerance of NHCC by activating its own expression under short-term heat stress (HS). Additionally, BcWRKY23 was found to bind to the promoter of BcWRKY25 and activate its expression, which also enhanced thermotolerance. BcWRKY23 and BcWRKY25 enhanced the expression of HSR genes to improve thermotolerance. Furthermore, BcPAL1 was shown to be activated by BcWRKY23, while BcPAL2 was activated by both BcWRKY23 and BcWRKY25. Overexpression of BcPAL1 and BcPAL2 in NHCC significantly increased thermotolerance, accompanied by an enhancement of phenylalanine ammonia-lyase (PAL) activity. Moreover, under long-term HS, the significant accumulation of BcVQ11A was observed, and the interaction between BcVQ11A and BcWRKY23 as well as BcWRKY25 inhibited the activation of them to target genes, resulting in decreased PAL activity. This study proposes a HS response pathway involving BcVQ11A-BcWRKY23-BcWRKY25-BcPAL1/BcPAL2, providing valuable insights into the molecular mechanisms underlying thermotolerance in plants.

Biosynthesis of Phenolic Compounds of Medicago truncatula After Inoculation with Selected PGPR Strains.

The phenylpropanoid biosynthesis pathway is involved in the response of plants to stress factors, including microorganisms. This paper presents how free-living strains of rhizobacteria Pseudomonas brassicacearum KK5, P. corrugata KK7, Paenibacillus borealis KK4, and the symbiotic strain Sinorhizobium meliloti KK13 affect the expression of genes encoding phenylalanine ammonia-lyase (PAL), the activity of this enzyme, and the production of phenolic compounds in Medicago truncatula. Seedlings were inoculated with rhizobacteria, then at T0, T24, T72, and T168 after inoculation, the leaves and roots were analyzed for gene expression, enzyme activity, and the content of phenolic compounds. All bacteria affected PAL gene expression, in particular, MtPAL2, MtPAL3, and MtPAL4. Pseudomonas strains had the greatest impact on gene expression. The inoculation affected PAL activity causing it to increase or decrease. The most stimulating effect on enzyme activity was observed 168 h after inoculation. A varied effect was also observed in the case of the content of phenolic compounds. The greatest changes were observed 24 h after inoculation, especially with the KK7 strain. The influence of the studied rhizobacteria on the biosynthesis of phenolic compounds at the molecular level (expression of MtPAL genes) and biochemical level (PAL activity and content of phenolic compounds) was confirmed. The MtPAL3 gene underwent the most significant changes after inoculation and can be used as a marker to assess the interaction between M. truncatula and rhizobacteria. The Pseudomonas strains had the greatest influence on the biosynthesis pathway of phenolic compounds.

Manipulating flavonoid biosynthesis in Trigonella persica through controlled spectral lighting

Trigonella persica Boiss., is renowned for its rich phytochemical profile, particularly the presence of the flavonol quercetin. This study explored the effects of various light treatments, including blue, red, blue-red (1:1) radiation (BRR), and pink fluorescent light (PFL), on the biochemical and molecular mechanisms governing quercetin and flavonoid biosynthesis in T. persica at different growth stages. Our results showed that light treatments significantly influenced the activity of key enzymes phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL) during germination and vegetative growth, with blue light inducing higher PAL and TAL activities compared to control conditions. High-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) analyses revealed that 48-h-old sprouts grown under red light exhibited the highest levels of flavonoid components and phenolic acids, with catechin as the predominant flavonoid. Notably, BRR treatment led to elevated concentrations of the bioavailable quercetin-3-rhamnoside in 48-h-old sprouts, while 15-day-old plants grown under PFL conditions showed a significant accumulation of the sulfated quercetin-3-sulfate. Real-time PCR analysis demonstrated that BRR upregulated the expression of flavonoid biosynthesis genes PAL, chalcone synthase (CHS), and chalcone isomerase (CHI) in sprouts, whereas PFL treatment induced higher expression of these genes, as well as cinnamate 4-hydroxylase (C4H), in aerial parts. These findings suggest that targeted light treatments, particularly blue and red LED light, can enhance the accumulation of bioavailable quercetin-3-rhamnoside during T. persica germination and sprouts exhibit higher levels of flavonoids and phenolic acids than aerial parts during different vegetative growth stages.