Accumulation Of Phenolic Compounds Research Articles

Strigolactone modulates phenolic acid accumulation and thereby improves tolerance to UV-B stress in Rhododendron chrysanthum Pall.

Multi-omics studies have shown that strigolactone modulates phenolic acid accumulation in the leaves of R. chrysanthum and can enable it to cope with UV-B stress. UV-B stress is an abiotic stress that plants will inevitably suffer during growth and can seriously affect the normal physiological state of plants. Strigolactone, a phytohormone, has been less studied and it is important to investigate its regulation of plant growth under UV-B radiation. In the present study, we investigated the changes in leaves of Rhododendron chrysanthum Pall. (R. chrysanthum) under UV-B radiation. The leaves of R. chrysanthum were collected for widely targeted metabolomics, hormonomics, transcriptomics, proteomics and acetylated proteomics assays. The results showed that the leaves of R. chrysanthum were able to produce a large amount of differential phenolic acids with antioxidant effects under UV-B stress, the content of strigolactone was significantly elevated, and the genes and proteins involved in phenolic acid biosynthesis and strigolactone biosynthesis were significantly altered, and some of the proteins (ASP1, 4CLL7, and CCD1) underwent acetylation modification. Meanwhile, correlation analysis showed that strigolactone was strongly correlated with differential phenolic acids, which might regulate the adaptive responses of the R. chrysanthum under UV-B stress. In this paper, we investigated the effects of strigolactone on the accumulation of phenolic acid compounds and found a strong correlation between strigolactone and elevated phenolic acid levels, which provided insights into the molecular mechanism of plant regulation of phenolic acid accumulation, and facilitated the adoption of measures to mitigate the adverse effects of UV-B stress on plant growth, and to achieve the purpose of protecting plant germplasm resources.

The effect of supplemental LED lighting in the range of UV, blue, and red wavelengths at different ratios on the accumulation of phenolic compounds in pak choi and swiss chard

Phenolic compounds are known for their health-promoting effects on humans. Pak choi (Brassica rapa ssp. chinensis) and Swiss chard (Beta vulgaris subsp. vulgaris) are used here as model plants, as they are eaten raw as baby leaf lettuce and differ in their phenolic compound profile while showing similar morphology. In a greenhouse an artificial light source with UV-B (215 mW m−2), blue (104 μmol/m−2 s−1) and red (245 μmol/m−2 s−1) LEDs was implemented to increase phenolic compounds during the last days before harvest. Pak choi shows an increase or trend towards an increase in the monoacylated triglycosides of kaempferol and quercetin after 4 days of irradiation for 4 h each. For example kaempferol-3-caffeoyl-sophoroside-7-glucoside was increased at low PAR values in the third run and red-dominated light treatment by up to 120 %. In addition, it was observed that the red variety ‘Amur’ has higher concentrations of quercetin glycosides which were increased often. In swiss chard, on the other hand, there was only a sporadic increase in vitexin glycosides. Despite very different concentrations in some samples, 2″-glucosyl-vitexin and 2′′-glucosyl-6′′-malonyl-vitexin showed significant increases of up to 350 % in the two chard varieties Lukullus and Rhubarb chard. The results suggest that the exposure time or intensity of UV-B radiation needs to be optimized for each species and has not yet consistently led to an increase but trends in phenolic compounds and in antioxidant activity in this study.

Rice OsDof12 enhances tolerance to drought stress by activating the phenylpropanoid pathway.

Drought is a major abiotic stress that severely affects cereal production worldwide. Although several genes have been identified that enhance the ability of rice to withstand drought stress, further research is needed to fully understand the molecular mechanisms underlying the response to drought stress. Our study showed that overexpression of rice DNA binding with one finger 12 (OsDof12) enhances tolerance to drought stress. Rice plants overexpressing OsDof12 (OsDof12-OE) displayed significantly higher tolerance to drought stress than the parental japonica rice "Dongjin". Transcriptome analysis revealed that many genes involved in phenylpropanoid biosynthesis were upregulated in OsDof12-OE plants, including phenylalanine ammonia-lyase 4 (OsPAL4), OsPAL6, cinnamyl alcohol dehydrogenase 6 (CAD6), and 4-coumarate-coA ligase like 6 (4CLL6). Accordingly, this transcriptional alteration led to the substantial accumulation of phenolic compounds, such as sinapic acids, in the leaves of OsDof12-OE plants, effectively lowering the levels of reactive oxygen species. Notably, OsDof12 bound to the AAAG-rich core sequence of the OsPAL4 promoter and promoted transcription. In addition, GIGANTEA (OsGI) interacts with OsDof12 in the nucleus and attenuates the transactivation activity of OsDof12 on OsPAL4. Our findings reveal a novel role for OsDof12 in promoting phenylpropanoid-mediated tolerance to drought stress.

Enhancing Phenolic Profiles in ‘Cabernet Franc’ Grapes Through Chitooligosaccharide Treatments: Impacts on Phenolic Compounds Accumulation Across Developmental Stages

High-quality grape raw materials are fundamental for producing premium wine. Ensuring the quality of grape raw materials, particularly enhancing their phenolic profiles, significantly improves wine flavor. Therefore, this study focused on ‘Cabernet Franc’ grapes, where a 0.1% chitooligosaccharide (COS) solution was foliar sprayed during the green pea stage, the onset of veraison stage, and the mid-ripening stage to investigate the impact of exogenous COS treatment on the accumulation of phenolic compounds in grape berries. The results revealed that COS treatment during the green pea and the onset of veraison stages significantly increased the levels of total phenolic, total flavonoid, and total anthocyanin in grapes, with distinct effects on flavanols, phenolic acids, flavonols, and stilbenes, respectively. Eight key compounds most significantly influenced by the treatment were identified through orthogonal partial least squares discriminant analysis (OPLS-DA) and machine learning screening. Specifically, treatment during the green pea stage had a significant impact on total soluble solids, proanthocyanidin B1, catechin, and vanillic acid, while veraison treatment notably affected petunidin-3-O-(6″-O-p-coumaryl)-glucoside, cyanidin-3-O-(6″-O-p-coumaryl)-glucoside, cyanidin-3-O-glucoside and isorhamnetin. This study could provide valuable data references and theoretical support for applying COS in wine grapes and regulating high-quality raw materials.

Dwarfism mechanism in Malus clonal rootstocks.

The dwarfing mechanism in apple clonal rootstocks is driven by complex interactions between anatomical, hormonal, genetic, and phenolic factors, offering potential for advanced genetic manipulation to optimize tree size and enhance orchard productivity. The widespread adoption of dwarfing rootstocks is pivotal to modern commercial apple (Malus × domestica Borkh) orchards due to their ability to control tree size, shorten the juvenile period, and enhance reproductive growth and overall productivity. The underlying mechanisms of rootstock-induced dwarfism are multifaceted and involve interactions between phenotypic, anatomical, genetic, and phytohormonal factors. This review consolidates current understanding, highlighting the importance of auxin (IAA), cytokinins (CKs), gibberellins (GAs), and abscisic acid (ABA) in mediating growth suppression through impaired transport and hormone signaling. The phenotypic impacts, including reduced root growth, shorter sylleptic shoots, and higher floral bud densities, are discussed alongside genetic loci such as Dw1, Dw2, and Dw3, and the influence of key genes/TFs like MdWRKY9, RGL, and PIN. Anatomically, dwarf rootstocks exhibit a higher bark-to-wood ratio and restricted hydraulic conductivity, which contribute to reduced scion vigour. Furthermore, the accumulation of phenolic compounds in the graft union of dwarfing rootstocks further modulates the growth inhibition. These insights lay the groundwork for advanced molecular breeding strategies, incorporating gene-editing technologies to improve dwarf rootstock development, providing avenues for enhanced orchard management and apple productivity.

Comparative Study on the Response of Hyssop (Hyssopus officinalis L.), Salvia (Salvia officinalis L.), and Oregano (Origanum vulgare L.) to Drought Stress Under Foliar Application of Selenium.

Drought is one of the most important abiotic factors limiting plant productivity. Although the aromatic plants of the Lamiaceae family often grow in arid regions, drought tolerance varies greatly among the different species of this family. The effect of induced drought stress can be reduced by the application of selenium. The current study aims to compare the growth and biochemical responses of three species of the Lamiaceae family (hyssop, salvia, and oregano) to drought stress and the possibility of reducing the effect of stress in these plants by foliar treatment with selenium. Drought stress reduced the fresh and dry biomass of hyssop (by 35% and 15%), salvia (by 45% and 41%), and oregano (by 51% and 32%). Se treatment did not affect the growth of plants under drought stress, but it improved relative water content in hyssop and salvia under moderate drought conditions. A reduction in the content of chlorophyll a and chlorophyll b (in hyssop and salvia). In addition, an increase in the content of hydrogen peroxide (in oregano and salvia), malondialdehyde, and proline in plants cultivated under drought conditions was observed. Se treatment led to reduced levels of hydrogen peroxide and malondialdehyde, along with an increase in chlorophyll a content (in hyssop and oregano) and proline content. The response of the antioxidant system depended on the plant species. Hyssop exhibited a significant increase in glutathione peroxidase, superoxide dismutase, and peroxidase activities. Oregano showed enhanced catalase activity. Salvia experienced a sharp increase in ascorbic acid content. Se treatment stimulated the accumulation of phenolic compounds and increased glutathione peroxidase activity in all studied species.

Evaluation of Bioactive Compounds and Antioxidant Activity of Green and Red Kale (Brassica oleracea L. var. acephala) Microgreens Grown Under White, Red, and Blue LED Combinations

Microgreens have great potential for improving the nutritional value of human diets, as well as constituting a promising dietary option for preventing chronic disease. Light-emitting diodes (LEDs) are commercially used as a light source to improve the growth of microgreens, as well as nutrient and bioactive compound accumulation. Here, we provide the first report of the phenolic compound, chlorophyll and carotenoid pigment, and dietary fiber contents of red and green kale microgreens grown in a growth chamber under white LEDs combined with red or blue light. Significant differences in the response of phytocompounds between white light and its combination with blue or red LEDs were determined. These studies showed that a combination of white and blue LEDs positively influenced the accumulation of phenolic compounds, which consequently determined high antioxidant activity. On the contrary, the white LED lights were the most suitable for the accumulation of carotenoids and chlorophylls, including chlorophyll a and b, and Klason lignin. These results suggest that the use of a combination of white light with blue or red light can increase the concentration of phenolic compounds and dietary fiber in red and green kale microgreens and thus may enhance their health-promoting potential.

Alleviation of NaCl Stress on Growth and Biochemical Traits of Cenchrus ciliaris L. via Arbuscular Mycorrhizal Fungi Symbiosis

Soil salinization, especially in arid and semi-arid regions, is one of the major abiotic stresses that affect plant growth. To mediate and boost plant tolerance against this abiotic stress, arbuscular mycorrhizal fungi (AMF) symbiosis is commonly thought to be an effective tool. So, the main purpose of this study was to estimate the role of AMF (applied as a consortium of Claroideoglomus etunicatum Claroideoglomus eutinicatum, Funneliformis mosseae Funliformis mosseae, Rhizophagus fasciculatum, and R. intraradices species) symbiosis in mitigating deleterious salt stress effects on the growth parameters (shoot length (SL), root length (RL), shoot dry weight (SDW), root dry weight (RDW), root surface area (RSA), total root length (TRL), root volume (RV), root diameter (RD), number of nodes and leaves) of Cenchrus ciliaris L. plants through improved accumulations of photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll), proline and phenolic compounds. The results of this experiment revealed that the roots of C. ciliaris plants were colonized by AMF under all the applied salinity levels (0, 75, 150, 225, and 300 mM NaCl). However, the rate of colonization was negatively affected by increasing salinity as depicted by the varied colonization structures (mycelium, vesicles, arbuscules and spores) which were highest under non-saline conditions. This association of AMF induced an increase in the growth parameters of the plant which were reduced by salinity stress. The improved shoot/root indices are likely due to enhanced photosynthetic activities as the AMF-treated plants showed increased accumulation of pigments (chlorophyll a, chlorophyll b and total chlorophyll), under saline as well as non-saline conditions, compared to non-AMF (N-AMF) plants. Furthermore, the AMF-treated plants also exhibited enhanced accumulation of proline and phenolic compounds. These accumulated metabolites act as protective measures under salinity stress, hence explaining the improved photosynthetic and growth parameters of the plants. These results suggest that AMF could be a good tool for the restoration of salt-affected habitats. However, more research is needed to check the true efficacy of different AMF inoculants under field conditions.

Influence of Primary Light Exposure on the Morphophysiological Characteristics and Phenolic Compounds Accumulation of a Tea Callus Culture (Camellia sinensis L.).

Tea plant calli (Camellia sinensis L.) are characterized by the accumulation of various phenolic compounds (PC)-substances with high antioxidant activity. However, there is still no clarity on the response of tea cells to light exposure of varying intensity. The purpose of the research was to study tea callus cultures grown under the influence of primary exposure to different light intensities (50, 75, and 100 µmol·m-2·s-1). The cultures' growth, morphology, content of malondialdehyde and photosynthetic pigments (chlorophyll a and b), accumulation of various PC, including phenylpropanoids and flavanols, and the composition of catechins were analyzed. Primary exposure to different light intensities led to the formation of chloroplasts in tea calli, which was more pronounced at 100 µmol·m-2·s-1. Significant similarity in the growth dynamics of cultures, accumulation of pigments, and content of malondialdehyde and various phenolics in tea calli grown at light intensities of 50 and 75 µmol·m-2·s-1 has been established, which is not typical for calli grown at 100 µmol·m-2·s-1. According to data collected using high-performance liquid chromatography, (+)-catechin, (-)-epicatechin, epigallocatechin, gallocatechin gallate, epicatechin gallate, and epigallocatechin gallate were the main components of the tea callus culture's phenolic complex. Its content changed under the influence of primary exposure to light, reaching the greatest accumulation in the final stages of growth, and depended on the light intensity. The data obtained indicate changes in the morphophysiological and biochemical characteristics of tea callus cultures, including the accumulation of PC and their individual representatives under primary exposure to light exposure of varying intensity, which is most pronounced at its highest values (100 µmol·m-2·s-1).

Effect of the Phenological Stage on the Phenolic Composition, and Antioxidant and Antimicrobial Properties of Cirsium vulgare (Savi) Ten. Extracts.

Cirsium vulgare (Savi) Ten. is a plant from the Asteraceae family that is commonly used in traditional medicine. The purpose of this work was to investigate the antioxidant and antimicrobial characteristics of phenolic compounds found in ethanol and dry extracts of C. vulgare leaves, inflorescence, and roots during various phenological stages. Apigenin-7-O-glucoside and chlorogenic acid were identified in practically all C. vulgare extracts. Extracts from leaves collected at the end of the phenological dormancy period and in the first growing year had the highest antioxidant (cupric ion-reducing antioxidant capacity of 12,938 Trolox equivalents/g dry weight) and antimicrobial activity (against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Proteus vulgaris, and Candida albicans) with MIC values of ethanol extract from 16.7 mg/mL to 8.35 mg/mL. These extracts included a high concentration of chlorogenic acid and apigenin-7-O-glucoside. Also, dry extracts from C. vulgare roots and inflorescences showed a higher antimicrobial effect compared to ethanolic extracts with MIC values from 5.57 mg/mL to 3 mg/mL. The study emphasizes the critical role of phenological stages and raw material composition in the accumulation of phenolic compounds and their biological activity in C. vulgare. The findings suggest that extracts from C. vulgare leaves, especially those collected at the end of the phonological dormancy period, are promising candidates for further research into bioactive compounds with potential medicinal applications. The strong antioxidant and antibacterial properties of these extracts highlight their potential for development into natural pharmaceutical products.

Effects of chitosan hydrolysate on control of postharvest infection caused by Botrytis cinerea and physiological responses of wounded tomato fruit

Chitosan is considered an eco-friendly plant protection agent. Chitosan hydrolysate (CH) with an average molecular weight (MW) of the main fraction of 135 × 103 Da, with a deacetylation degree (DD) of 93 % is an unfractionated product of nitric acid hydrolysis of high molecular weight chitosan. The effect of the CH on gray mold caused by Botrytis cinerea in tomato fruit stored at 25 °C was investigated. Chitosan provided effective control of B. cinerea on tomato fruit. The CH treatment of wounded tomato fruit had a protective effect, reducing the percentage of infected fruit on the 7 d after treatment to 50 %, compared with untreated wounded fruit (69 %) and water-treated fruit (88 %). The protective effect of the CH in tomato fruit may be due to a direct fungitoxic action against the pathogen. It was found that the CH induced an immune response in tomato fruit via the accumulation of phenolic compounds. The level of phenolic compounds in the CH group was higher than in the untreated wound group from day 1 to 5, with a maximum reached on day 3 (113 mg-eq GA kg-1). No significant differences were found in the activities of peroxidase, phenylalanine ammonia lyase, polyphenol oxidase, β-1,3-glucanase and chitinase. Thus, the CH affects the processes occurring during fruit damage and contributes to the preservation of the consumer qualities of fruit.

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.

Physiological and Biochemical Effects of Intermittent Warming on 'Marmandi' Turning Tomato Fruits During Low-Temperature Storage

This experiment was conducted on the variety 'Marmandi' turning tomato fruits to investigate the effect of intermittent warming temperatures during extended low chilling temperature storage (21 days) on the subsequent ripening quality of tomato fruits. The quality was measured by assessing the quantitative amount of total phenolic compounds, chlorogenic acid, and ascorbic acid, as well as the development of fruit color and the evaluation of chilling injury (CI) symptoms. The results indicated that the amounts of total phenolic compounds and chlorogenic acid increased significantly during continuous low-temperature storage and after subsequent transfer to room temperature, with this increase being associated with significant loss of ascorbic acid. More frequent periods of intermittent warming (IW) during low-temperature storage were very effective in significantly decreasing the rate of accumulation of phenolic compounds, chlorogenic acid, and ascorbic acid losses. A significant reciprocal relationship between the amounts of chlorogenic acid and ascorbic acid was observed. Additionally, the results showed that as IW time increased, its effectiveness in retarding CI significantly improved.

Modifying the Ambient Light Spectrum Using LED Lamps Alters the Phenolic Profile of Hydroponically Grown Greenhouse Lettuce Plants without Affecting Their Agronomic Characteristics.

The growth and development of green lettuce plants can be modulated by the prevailing light conditions around them. The aim of this study was to evaluate the effect of ambient light enrichment with different LED light spectra on agronomic characteristics, polyphenol concentration and relative gene expression of enzymes associated with polyphenol formation in 'Levistro' lettuce grown hydroponically in a Nutrient Film Technique (NFT) system for 28 days in a greenhouse. The spectra (blue:green:red:far-red) and red:blue (R:B) ratios obtained by enriching ambient light with Blue (B), White (W), Blue-Red (BR) and Red (R) LED light were B: 47:22:21:10, 0.5:1; W: 30:38:23:9, 0.8:1; BR: 33:15:44:8, 1.3:1 and R: 16:16:60:8, 3.8:1, respectively, and photosynthetically active radiation (PAR) under the different treatments, measured at midday, ranged from 328 to 336 µmoles m-2 s-1. The resulting daily light integral (DLI) was between 9.1 and 9.6 mol m-2 day-1. The photoperiod for all enrichment treatments was 12 h of light. The control was ambient greenhouse light (25:30:30:15; R:B = 1.2:1; PAR = 702 µmoles m-2 s-1; DLI = 16.9 mol m-2 day-1; photoperiod = 14.2 h of light). Fresh weight (FW) and dried weight percentage (DWP) were similar among the enrichment treatments and the control. The leaf number increased significantly under BR and R compared to B lights. The relative index of chlorophyll concentration (RIC) increased as plants grew and was similar among the enrichment treatments and the control. On the other hand, the concentration of chlorogenic acid and chicoric acid increased under BR and B lights, which was consistent with the higher relative expression of the coumarate 3-hydroxylase enzyme gene. In view of the results, it is inferred that half of the PAR or DLI is sufficient to achieve normal growth and development of 'Levistro' lettuce plants, suggesting a more efficient use of light energy under the light enrichment treatments. On the other hand, the blue and combined blue-red lights promoted the accumulation of phenolic compounds in the leaves of 'Levistro' lettuce plants.

Calcium signaling regulates the accumulation of phenolic acids in response to UV-B stress in Rhododendron chrysanthum Pall.

This study, using multi-omics combined with physiologic assays, found that calcium-ion signaling can regulate phenolic acid accumulation in R. chrysanthum leaves in response to UV-B stress. UV-B stress is a severe abiotic stress capable of destroying cellular structures and affecting plant growth. Rhododendron chrysanthum Pall. (R. chrysanthum) is a plant that has been exposed to high levels of UV-B radiation for an extended period, leading to the development of adaptive responses to mitigate UV-B stress. As such, it serves as a valuable experimental material for studying plant resilience to UV-B stress. We utilized R. chrysanthum as the experimental material and subjected it to UV-B stress. We conducted a comprehensive analysis of the changes in R. chrysanthum under both control and UV-B stress conditions using multi-omic and physiologic assays. Our aim was to investigate the molecular mechanism underlying R. chrysanthum's resistance to UV-B stress, with a focus on calcium-ion signaling. UV-B stress was found to impact the photosynthesis of R. chrysanthum by decreasing the maximum photosynthetic efficiency of photosystem II, reducing Fm, and increasing F0. In addition, the composition of numerous phenolic acid compounds was significantly altered. Genes and proteins related to calcium signaling showed significant differences, with some proteins (CML, CPK1, CRK3, ATP2C, ERG3, CAR7) being modified by acetylation. The correlation between genes and proteins involved in calcium signaling and phenolic compounds suggested that calcium signaling may play a role in regulating the accumulation of phenolic compounds under UV-B stress to help R. chrysanthum adapt. This study examines the impact of calcium-ion signaling on the accumulation of phenolic acid compounds, offering insights for future research on the molecular mechanisms underlying plant resilience to UV-B stress.

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.

Theanine enhances resistance to Botrytis cinerea in postharvest strawberry fruit via modulating cell-wall and phenylpropanoid metabolisms

Theanine (N-ethyl-γ-glutamine), as a unique non-protein amino acid, plays vital roles in abiotic stress resistance, while its roles in biotic stress resistance are still unclear. Gray mold caused by Botrytis cinerea is a major disease in strawberries. Effects of theanine on the development of gray mold, cell-wall and phenylpropanoid metabolisms in strawberries were investigated in this study. Results showed that 5 mmol L−1 theanine treatment reduced disease incidence and severity of gray mold in strawberries with antifungal activity in vitro. Meanwhile, theanine treatment enhanced the accumulation of phenolic compounds and lignin, especially ellagic acid, cyanidin, and quercetin, which was associated with increased phenylpropanoid pathway related enzyme activities. Moreover, theanine induced callose deposition and suppressed cell- wall disassembling enzymes, accompanied by higher levels of water insoluble pectin, hemicellulose and cellulose. Therefore, theanine treatment could alleviate decay of B. cinerea-inoculated strawberries by regulating phenylpropanoid and cell-wall metabolisms, maintaining higher levels of phenolic compounds and cell-wall components, thereby contributing to disease resistance and cell-wall structure integrity.

Antifungal Activity of Disalt of Epipyrone A from Epicoccum nigrum Likely via Disrupted Fatty Acid Elongation and Sphingolipid Biosynthesis.

Multidrug-resistant fungal pathogens and antifungal drug toxicity have challenged our current ability to fight fungal infections. Therefore, there is a strong global demand for novel antifungal molecules with the distinct mode of action and specificity to service the medical and agricultural sectors. Polyenes are a class of antifungal drugs with the broadest spectrum of activity among the current antifungal drugs. Epipyrone A, a water-soluble antifungal molecule with a unique, linear polyene structure, was isolated from the fungus Epiccocum nigrum. Since small changes in a compound structure can significantly alter its cell target and mode of action, we present here a study on the antifungal mode of action of the disalt of epipyrone A (DEA) using chemical-genetic profiling, fluorescence microscopy, and metabolomics. Our results suggest the disruption of sphingolipid/fatty acid biosynthesis to be the primary mode of action of DEA, followed by the intracellular accumulation of toxic phenolic compounds, in particular p-toluic acid (4-methylbenzoic acid). Although membrane ergosterol is known to be the main cell target for polyene antifungal drugs, we found little evidence to support that is the case for DEA. Sphingolipids, on the other hand, are known for their important roles in fungal cell physiology, and their biosynthesis has been recognized as a potential fungal-specific cell target for the development of new antifungal drugs.

Alteration of stress-physiological mechanisms in sRNA-treated sweet corn plants during MDMV infection.

Maize dwarf mosaic virus (MDMV) can significantly reduce the growth and development of susceptible varieties of sweet corn. The virus utilises the energy and reserve sources of plant cells to ensure its reproduction in the microspaces formed by cell membranes. Therefore, the severity of stress can be monitored by examining certain physiological changes, for example, changes in the degree of membrane damage caused by lipid peroxidation, as well as changes in the amount of photosynthetic pigments. The activation of antioxidant enzymes (e.g. ascorbate peroxidase, guaiacol peroxidase, glutathione reductase) and the accumulation of phenolic compounds with antioxidant properties can indirectly protect against the oxidative stress caused by the presence of the positive orientation, single-stranded RNA-virus. This study demonstrates the changes in these physiological processes in a sweet corn hybrid (Zea mays cv. saccharata var. Honey Koern.) susceptible to MDMV infection, and suggests that exogenous small RNA treatment can mitigate the damage caused by virus infection.

Recovery of Scots Pine Seedlings from Long-Term Zinc Toxicity.

We studied the recovery of the growth and physiological parameters of Scots pine seedlings after long-term zinc toxicity. The removal of excess zinc from the nutrient solution resulted in the rapid recovery of primary root growth but did not promote the initiation and growth of lateral roots. The recovery of root growth was accompanied by the rapid uptake of manganese, magnesium, and copper. Despite the maximum rate of manganese uptake by the roots, the manganese content in the needles of the recovering plants did not reach control values during the 28 days of the experiment, unlike magnesium, iron, and copper. In general, the recovery of ion homeostasis eliminated all of the negative effects on the photosynthetic pigment content in the needles. However, these changes, along with recovery of the water content in the needles, were not accompanied by an increase in the weight gain of the recovering seedlings compared with that of the Zn-stressed seedlings. The increased accumulation of phenolic compounds in the needles persisted for a long period after excess zinc was removed from the nutrient solution. The decreased lignin content in the roots and needles is a characteristic feature of Zn-stressed plants. Moreover, the removal of excess zinc from the nutrient solution did not lead to an increase in the lignin content in the organs.