Methyl jasmonate affects phenolic metabolism and gene expression in blueberry (Vaccinium corymbosum)

Effect of foliar application of bio-stimulants on growth, yield and nutritional quality of broccoli

Broccoli is one of important cole crop grown all over the world due to its unique nutritional profile consumed fresh as well as processed. It contains a wide range of nutrients, vitamins, minerals and specific anti-cancer compounds such as glucosinolates. Broccoli cultivation in Pakistan is increasing rapidly, however, till now there is no standardized cropping technology for broccoli cultivation under local climate. Considering research gap (lack of suitable varieties, poor growth, and unavailability of optimized crop technology), trial was conducted at Vegetable research area, Institute of Horticultural Sciences, University of Agriculture, Faisalabad to evaluate the impact of bio-stimulants on different broccoli cultivars under local climatic conditions. The set of experimental treatments was laid out in Randomized Complete Block Design (RCBD) with three replications. Pre-harvest application of Isabion and Seaweed extract significantly enhanced the plant height (11%), dry weight (4%), leaf area (7%), and yield plant-1 (5%). Moreover, Isabion and seaweed extract application led to the increase in antioxidant enzymes i.e., superoxide dismutase (18%), peroxidase (38%) and catalase (12%). In crux, the foliar application of bio-stimulants (Isabion and seaweed extract) on broccoli enhanced the growth, yield, and contents of antioxidant enzymes.

The Influence of Methyl Jasmonate on Expression Patterns of Rosmarinic Acid Biosynthesis Genes, and Phenolic Compounds in Different Species of Salvia subg. Perovskia Kar L

Salvia yangii B.T. Drew and Salvia abrotanoides Kar are two important fragrant and medicinal plants that belong to the subgenus Perovskia. These plants have therapeutic benefits due to their high rosmarinic acid (RA) content. However, the molecular mechanisms behind RA generation in two species of Salvia plants are still poorly understood. As a first report, the objectives of the present research were to determine the effects of methyl jasmonate (MeJA) on the rosmarinic acid (RA), total flavonoid and phenolic contents (TFC and TPC), and changes in the expression of key genes involved in their biosynthesis (phenylalanine ammonia lyase (PAL), 4-coumarate-CoA ligase (4CL), and rosmarinic acid synthase (RAS)). The results of High-performance liquid chromatography (HPLC) analysis indicated that MeJA significantly increased RA content in S. yungii and S. abrotanoides species (to 82 and 67 mg/g DW, respectively) by 1.66- and 1.54-fold compared with untreated plants. After 24 h, leaves of Salvia yangii and Salvia abrotanoides species treated with 150 M MeJA had the greatest TPC and TFC (80 and 42 mg TAE/g DW, and 28.11 and 15.14 mg QUE/g DW, respectively), which was in line with the patterns of gene expression investigated. Our findings showed that MeJA dosages considerably enhanced the RA, TPC, and TFC contents in both species compared with the control treatment. Since increased numbers of transcripts for PAL, 4CL, and RAS were also detected, the effects of MeJA are probably caused by the activation of genes involved in the phenylpropanoid pathway.

Mechanism of Zn alleviates Cd toxicity in mangrove plants (Kandelia obovata)

Cadmium (Cd) pollution is very common and serious in mangrove ecosystems in China. Zinc (Zn) has been used to reduce Cd accumulation in plants, and phenolic acid metabolism plays an important role in plant response to stress. In present study, in order to clarify whether Zn alleviates Cd toxicity in mangrove plants through phenolic acid metabolism, the Cd-contaminated Kandelia obovata plants were treated with different concentrations of (0, 80,300, and 400 mg·kg^-1) ZnSO₄ in a set of pot experiments and the biomass, the contents of Cd, Zn, soluble sugar, chlorophyll and the activities of 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric-reducing antioxidant power (FRAP), l-phenylalanine ammonia-lyase (PAL), shikimic acid dehydrogenase (SKDH), cinnamyl alcohol dehydrogenase (CAD) and polyphenol oxidase (PPO) in the leaves were analyzed. The results showed that Cd contents in the leaves of Kandelia obovata ranged from 0.077 to 0.197 mg·kg^-1 under different treatments, and Zn contents ranged from 90.260 to 114.447 mg·kg^-1. Low-dose ZnSO₄ treatment (80 mg·kg^-1) performed significant positive effects on the biomass, phenolic acid metabolism-related enzyme activities, antioxidant capacity, and chlorophyll and soluble sugar contents in the leaves of Cd-contaminated mangrove plants. At the meantime, the addition of low-dose ZnSO₄ promoted the biosynthesis of hydroxycinnamic acid, hydroxybenzoic acid, and enhanced the plant antioxidant capacity, thus alleviated Cd toxicity in mangrove plants.

Methyl jasmonate induces selaginellin accumulation in Selaginella convoluta

INTRODUCTION

Selaginellins are specialized metabolites and chemotaxonomic markers for Selaginella species. Despite the growing interest in these compounds as a result of their bioactivities, they are accumulated at low levels in the plant. Hence, their isolation and chemical characterization are often difficult, time consuming, and limiting for biological tests. Elicitation with the phytohormone methyl jasmonate (MeJA) could be a strategy to increase the content of selaginellins addressing their low availability problem, that also impairs pharmacological investigations.

MATHERIALS AND METHODS

In this study, we examined MeJA elicitation in Selaginella convoluta plants, a medicinal plant found in northeastern Brazil, by treating them with two different concentrations (MeJA: 50 and 100 µM), followed by chemical profiling after 12, 24 and 48 h after application. Samples were harvested and analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS).

RESULTS AND DISCUSSCION

MeJA treatment significantly impacted the chemical phenotype. Regarding shoots differences in the time-dependent increased accumulation of all metabolites when plants were subjected to 100 µM MeJA were observed while in roots, most metabolites had their concentrations decreased in a time-dependent fashion at the same conditions. Results support organ, MeJA concentration and time post-treatment dependence of specialized metabolite accumulation, mainly the flavonoids and selaginellins. The amount of Selaginellin G in shoots of MeJA-treated specimens increased in 5.63-fold relative to control. The molecular networking approach allowed for the putative annotation of 64 metabolites, among them, the MeJA treatment followed by targeted metabolome analysis also allowed to annotate seven unprecedented selaginellins. Additionally, the in silico bioactive potential of the annotated selaginellins highlighted targets related to neurodegenerative disorders, antiproliferative, and antiparasitic issues. Taken together, data point out MeJA exposure as a strategy to induce potentially bioactive selaginellins accumulation in S. convoluta, this approach could enable a deep investigation about the metabolic function of these metabolites in the genus as well as regarding pharmacological exploration of the undervalued potential.

Benzothiadiazole enhances ascorbate recycling and polyphenols accumulation in blueberry in a cultivar-dependent manner

Benzothiadiazole (BTH) is a functional analogue of salicylic acid able to induce systemic acquired resistance in many horticultural crops. The aim of the work was to investigate how BTH may affect i) fruit quality, ii) ascorbic acid (AsA) oxidation and recycling metabolism and iii) phenolic compounds accumulation, during development and ripening of berries from the two selected cultivars. Blueberry (Vaccinium corymbosum L.) plants (cv 'Brigitta' and 'Duke') were treated with 0.118 mM BTH every two weeks during ripening, then all fruits of each plant were harvested and divided in four developmental stages. Results indicated that BTH had no marked effects on fruit quality parameters. During the first developmental stage, BTH negatively affected dry matter in both cv, while soluble solids and AsA content were affected in 'Duke'. In fully ripe berries, BTH reduced dry matter in 'Duke' and enhanced soluble solids content in 'Brigitta', while diminishing titratable acidity. AsA content was positively affected by BTH in 'Duke', but not in 'Brigitta'. The effect of BTH on the enzymes involved in AsA recycling was recorded in berries at the third (fruit more than half pigmented) and fourth developmental stages. After treatment, in both cv ascorbate peroxidase (APX) activity increased in fully ripe berries, while monodehydroascorbate reductase (MDHAR) activity was stimulated at the third ripening stage. Conversely, the activities of dehydroascorbate reductase (DHAR) and glutathione reductase (GR) were enhanced only in 'Brigitta' and in 'Duke', respectively. BTH stimulated total polyphenols, flavonoid and anthocyanin accumulation in 'Brigitta' and in 'Duke' at the third and fourth ripening stages. In fully ripe berries, BTH enhanced the accumulation of delphinidins, cyanidins, petunidins and peonidins in 'Brigitta', while in 'Duke' it increased all classes of anthocyanidins, including malvidin. On the contrary, the relative proportion of the individual anthocyanins was only slightly affected by BTH treatment, mainly regarding delphinidin and malvidin at the third and fourth stage of ripening of 'Duke' and 'Brigitta', respectively. These results show that preharvest BTH application can positively impact on fruit bioactive compounds levels, affecting AsA recycling and content and increasing polyphenols accumulation in fruit, but partly depending on cv and ripening stage.

Change in Secondary Metabolites and Expression Pattern of Key Rosmarinic Acid Related Genes in Iranian Lemon Balm (Melissa officinalis L.) Ecotypes Using Methyl Jasmonate Treatments

The medicinal herb, lemon balm (Melissa officinalis L.), which is high in rosmarinic acid (RA), has well-known therapeutic value. The goals of this study were to investigate the effects of methyl jasmonate (MeJA) on RA content, total phenolic content (TPC), and total flavonoid content (TFC), as well as changes in expression of their biosynthesis-related key genes (MoPAL, Mo4CL, and MoRAS) in Iranian lemon balm ecotypes, as first reported. Our results revealed that MeJA doses significantly increase the RA content, TPC, and TFC in both ecotypes compared with the control samples. Additionally, the higher expression levels of MoPAL, Mo4CL, and MoRAS following treatment were linked to RA accumulation in all treatments for both Iranian lemon balm ecotypes. After 24 h of exposure to 150 µM MeJA concentration, HPLC analysis showed that MeJA significantly increased RA content in Esfahan and Ilam ecotypes, which was about 4.18- and 7.43-fold higher than untreated plants. Our findings suggested that MeJA has a considerable influence on RA, TPC, and TFC accumulation in MeJA-treated Iranian M. officinalis, which might be the result of gene activation from the phenylpropanoid pathway. As a result of our findings, we now have a better understanding of the molecular processes behind RA production in lemon balm plants.

Phenolic profiles and their responses to pre- and post-harvest factors in small fruits: a review

The consumption of small fruits has increased in recent years. Besides their appealing flavor, the commercial success of small fruits has been partially attributed to their high contents of phenolic compounds with multiple health benefits. The phenolic profiles and contents in small fruits vary based on the genetic background, climate, growing conditions, and post-harvest handling techniques. In this review, we critically compare the profiles and contents of phenolics such as anthocyanins, flavonols, flavan-3-ols, and phenolic acids that have been reported in bilberries, blackberries, blueberries, cranberries, black and red currants, raspberries, and strawberries during fruit development and post-harvest storage. This review offers researchers and breeders a general guideline for the improvement of phenolic composition in small fruits while considering the critical factors that affect berry phenolics from cultivation to harvest and to final consumption.

Effects of Different Light Spectra on Final Biomass Production and Nutritional Quality of Two Microgreens

To improve microgreen yield and nutritional quality, suitable light spectra can be used. Two species-amaranth (Amaranthus tricolor L.) and turnip greens (Brassica rapa L. subsp. oleifera (DC.) Metzg)-were studied. The experiment was performed in a controlled LED environment growth chamber (day/night temperatures of 24 ± 2 °C, 16 h photoperiod, and 50/60% relative humidity). Three emission wavelengths of a light-emitting diode (LED) were adopted for microgreen lighting: (1) white LED (W); (2) blue LED (B), and (3) red LED (R); the photosynthetic photon flux densities were 200 ± 5 µmol for all light spectra. The response to light spectra was often species-specific, and the interaction effects were significant. Morphobiometric parameters were influenced by species, light, and their interaction; at harvest, in both species, the fresh weight was significantly greater under B. In amaranth, Chl a was maximized in B, whereas it did not change with light in turnip greens. Sugar content varied with the species but not with the light spectra. Nitrate content of shoots greatly varied with the species; in amaranth, more nitrates were measured in R, while no difference in turnip greens was registered for the light spectrum effect. Polyphenols were maximized under B in both species, while R depressed the polyphenol content in amaranth.

Preharvest application of prohydrojasmon affects color development, phenolic metabolism, and pigment-related gene expression in red pear (Pyrus ussuriensis)

BACKGROUND

Peel color is an economically relevant trait that influences the appearance and quality of red pear, whose red color is due to anthocyanin accumulation. Prohydrojasmon (PDJ), which has similar effects to endogenous jasmonates, was developed as a commercial bioregulator, particularly to improve fruits coloring. However, little information is available about the effect of PDJ on pears. This study investigated the effects of preharvest PDJ treatments on color development, phenolic compounds accumulation, and related gene expression in the red pear cultivar 'Nanhong'. The treatments were performed during the pre-color-change period by spraying 50 or 100 mg L^-1 of PDJ on fruits.

RESULTS

Preharvest PDJ treatments had a significant effect on color development, without affecting other quality parameters such as total soluble solids and fruit acidity. Liquid chromatography-mass spectrometry analysis showed that concentrations of anthocyanins and flavonols were enhanced in the peel after PDJ treatments, particularly when a concentration of 100 mg L^-1 was used, whereas those of hydroxycinnamates and flavanols were decreased. After PDJ application, the transcription levels of anthocyanin biosynthesis genes PAL, CHS, CHI, ANS, F3H, and UFGT were enhanced, especially under the higher PDJ concentration tested. In addition, anthocyanin accumulation in the peels of PDJ-treated fruits was found to be positively correlated with the upregulation of the regulatory gene MYB114.

CONCLUSION

Preharvest treatments with PDJ could be a useful tool to improve fruits coloring and increase phenolic content in pear. These findings also improve our understanding of the molecular mechanisms associated with PDJ-regulated anthocyanin accumulation in pear fruits.

Borage extracts affect wild rocket quality and influence nitrate and carbon metabolism

Market is increasingly demanding vegetables with high quality and nutraceutical characteristics. It was demonstrated that leafy vegetables can get benefit from biostimulants, for the reduction of nitrate concentration and the increment of antioxidants, with potential benefit for human health. The research purpose was to investigate on the role of a novel plant-based biostimulant in affecting nitrogen and carbon metabolism in wild rocket (Diplotaxis tenuifolia L.). Foliar spray treatments were performed with extracts obtained from borage (Borago officinalis L.) leaves and flowers. To evaluate the treatments effect, in vivo determinations (chlorophyll a fluorescence and chlorophyll content) were performed. At harvest, nitrate concentration, sucrose, total sugars, chlorophyll, and carotenoids levels were measured in leaves. In order to characterize the mechanism of action also at molecular level, a set of genes encoding for some of the key enzymes implicated in nitrate and carbon metabolism was selected and their expression was measured by qRT-PCR. Interesting results concerned the increment of sucrose, coherent with a high value of Fv/Fm, in addition to a significant reduction of nitrate and ABA than control, and an enhanced NR in vivo activity. Also, genes expression was influenced by extracts, with a more pronounced effect on N related genes.

The Anti-Proliferative and Anti-Invasive Effect of Leaf Extracts of Blueberry Plants Treated with Methyl Jasmonate on Human Gastric Cancer In Vitro Is Related to Their Antioxidant Properties

Gastric cancer is the third main cause of cancerous tumors in humans in Chile. It is well-accepted that a diet rich in antioxidant plants could help in fighting cancer. Blueberry is a fruit crop with a high content of antioxidants. Methyl jasmonate (MeJA) is a phytohormone involved in plant defenses under stress conditions. The exogenous application of MeJA can improve the antioxidant properties in plants. We studied in vitro and in vivo anticancer action on human gastric cancer (cell line AGS) and the antioxidant properties of extracts from blueberry plants untreated and treated with MeJA. The results demonstrated that leaf extracts displayed a higher inhibition of cancer cell viability as well as greater antioxidant properties compared to fruit extracts. Besides, MeJA applications to plants improved the antioxidant properties of leaf extracts (mainly anthocyanins), increasing their inhibition levels on cell viability and migration. It is noteworthy that leaf extract from MeJA-treated plants significantly decreased cancer cell migration and expression of gastric cancer-related proteins, mainly related to the mitogen-activating protein kinase (MAPK) pathway. Interestingly, in all cases the anticancer and antioxidant properties of leaf extracts were strongly related. Despite highlighted outcomes, in vivo results did not indicate significant differences in Helicobacter pylori colonization nor inflammation levels in Mongolian gerbils unfed and fed with blueberry leaf extract. Our findings demonstrated that MeJA increased antioxidant compounds, mainly anthocyanins, and decreased the viability and migration capacity of AGS cells. In addition, leaf extracts from MeJA-treated plants were also able to decrease the expression of gastric cancer-related proteins. Our outcomes also revealed that the anthocyanin-rich fraction of blueberry leaf extracts showed higher in vitro antiproliferative and anti-invasive effects than the crude leaf extracts. However, it is still uncertain whether the leaf extracts rich in anthocyanins of blueberry plants are capable of exerting a chemopreventive or chemoprotective effect against gastric cancer on an in vivo model.

Effects of Two Doses of Organic Extract-Based Biostimulant on Greenhouse Lettuce Grown Under Increasing NaCl Concentrations

The enhancement of plant tolerance toward abiotic stresses is increasingly being supported by the application of biostimulants. Salinity represents a serious problem in the Mediterranean region. To verify the effects deriving from the application of biostimulants, trials on Romaine lettuce plants under salt exposure were performed, in greenhouse. Plants were subjected to three NaCl solutions with 0.8, 1.3, and 1.8 dS/m of electrical conductivity. The volume of the solution was 200 mL/plant and delivered every 3 days. Biostimulant treatments started after crop establishment and were: control (water) and two doses (0.1 or 0.2 mL/plant) of the commercial biostimulant Retrosal® (Valagro S.p.A), containing calcium, zinc, and specific active ingredients. Four Retrosal® treatments were applied, every 7 days, directly to the substrate. Non-destructive analyses were conducted to assess the effects on leaf photosynthetic efficiency. At harvest, plants fresh weight (FW) and dry weight were determined, as well as the concentration of chlorophylls, carotenoids, total sugars, nitrate, proline, and abscisic acid (ABA). The biostimulant tested increased significantly the FW of lettuce (+65% in the highest dose) compared to controls. Results indicate that treatments positively affected the chlorophyll content measured in vivo (+45% in the highest dose) and that a general positive effect was observable on net photosynthesis rate. Retrosal® seems to improve the gas exchanges under our experimental conditions. The total sugars levels were not affected by treatments. Biostimulant allowed maintaining nitrate concentration similar to the untreated and unstressed controls. The increasing levels of water salinity caused a raise in proline concentration in control plants (+85%); biostimulant treatments at 0.2 mL/plant dose kept lower the proline levels. All plants treated with the biostimulant showed lower value of ABA (-34%) compared to controls. Results revealed that Retrosal® is able to stimulate plant growth independently from the salinity exposure. However, treated plants reached faster the commercial maturity stage. The fresh biomass of control at the end of experiment, after 30 days, ranged from 15 to 42 g/head, while in biostimulant treated plants ranged from 45 to 94 g/head. The product applied at maximum dose seems to be the most effective in our experimental conditions.

Variation of Anthocyanin Content and Profile Throughout Fruit Development and Ripening of Highbush Blueberry Cultivars Grown at Two Different Altitudes

Blueberry (Vaccinium corymbosum L.) is a widely consumed fruit and a rich source of bioactive compounds, namely, the polyphenol class of anthocyanins. Little information is available about the influence of internal (genetic and developmental) and external (environmental) factors on the levels of phenolic metabolites in blueberry fruit. In light of this consideration, total polyphenolic and flavonoid content, anthocyanin accumulation and composition were evaluated in cv. "Duke" and "Brigitta" grown at two different altitudes in Valtellina, a valley of the Alps in Northern Italy. During berry ripening, there is a developmentally coordinated shift from cyanidin-type, di-substituted anthocyanins toward delphinidin-based, tri-substituted pigments. At the lower altitude location, higher temperatures, not exceeding optimum, resulted in a more quickly berry developmental pattern and in higher anthocyanin concentrations in the early phases of ripening. At later stages of ripening, berries of both cultivars at higher altitude compensate for these initial temperature effects, and no differences were recorded in ripe fruit grown in the two locations. We conclude that anthocyanin accumulation is strongly regulated by development and genotype, and the environmental factors, associated to the altitude gradient, exert in the trial conditions only a fine-tuning influence. Fruits reach the full-ripening stage simultaneously at both sites because the initial gap in pigment levels is counterbalanced at the higher altitude by a faster rate of accumulation at later phases of the ripening process.

Stepwise response of MeJA-induced genes and pathways in leaves of C. roseus

Catharanthus roseus is a perennial herb known for the production of important terpenoid indole alkaloids (TIAs) in addition to a variety of phenolic compounds. The goal of the present work was to detect the prolonged effects of MeJA (6 uM) treatment across time (up to 24 days) in order to detect the stepwise response of MeJA-induced genes and pathways in leaves of C. rouses. Prolonged exposure of plants to MeJA (6 uM) treatment for different time points (6, 12 and 24 days) indicated that genes in the indole alkaloid biosynthesis pathway and upstream pathways were triggered earlier (e.g., 6 days) than those in the anthocyanin biosynthesis pathway and its upstream pathways (e.g., 12 days). Three enzymes, e.g., T16H, OMT, and D4H, in the six-step vindoline biosynthesis and two enzymes, e.g., TDC and STR, acting consecutively in the conversion of tryptophan to strictosidine, were activated after 6 days of MeJA treatment. Two other key enzymes, e.g., TRP and CYP72A1, acting concurrently upstream of the TIA biosynthesis pathway were upregulated after 6 days. The genes encoding TDC and STR might concurrently act as a master switch of the TIA pathway towards the production of the indole alkaloids. On the other hand, we speculate that the gene encoding PAL enzyme also acts as the master switch of phenylpropanoid biosynthesis and the downstream flavonoid biosynthesis and anthocyanin biosynthesis pathways towards the production of several phenolic compounds. PAL and the downstream enzymes were activated 12 days after treatment. Cluster analysis confirmed the concordant activities of the flower- and silique-specific bHLH25 transcription factor and the key enzyme in the TIA biosynthesis pathway, e.g., STR. Due to the stepwise response of the two sets of pathways, we speculate that enzymes activated earlier likely make TIA biosynthesis pathway a more favourable target in C. roseus than anthocyanin biosynthesis pathway.

Molecular Mechanism and Health Role of Functional Ingredients in Blueberry for Chronic Disease in Human Beings

Functional ingredients in blueberry have the best health benefits. To obtain a better understanding of the health role of blueberry in chronic disease, we conducted systematic preventive strategies for functional ingredients in blueberry, based on comprehensive databases, especially PubMed, ISI Web of Science, and CNKI for the period 2008⁻2018. Blueberry is rich in flavonoids (mainly anthocyanidins), polyphenols (procyanidin), phenolic acids, pyruvic acid, chlorogenic acid, and others, which have anticancer, anti-obesity, prevent degenerative diseases, anti-inflammation, protective properties for vision and liver, prevent heart diseases, antidiabetes, improve brain function, protective lung properties, strong bones, enhance immunity, prevent cardiovascular diseases, and improve cognitive decline. The anthocyanins and polyphenols in blueberry are major functional ingredients for preventive chronic disease. These results support findings that blueberry may be one of the best functional fruits, and further reveals the mechanisms of anthocyanins and polyphenols in the health role of blueberry for chronic disease. This paper may be used as scientific evidence for developing functional foods, nutraceuticals, and novel drugs of blueberry for preventive chronic diseases.

The Effect of Ethephon, Abscisic Acid, and Methyl Jasmonate on Fruit Ripening in Rabbiteye Blueberry (Vaccinium virgatum)

Ripening in blueberry fruit is irregular and occurs over an extended period requiring multiple harvests, thereby increasing the cost of production. Several phytohormones contribute to the regulation of fruit ripening. Certain plant growth regulators (PGRs) can alter the content, perception, or action of these phytohormones, potentially accelerating fruit ripening and concentrating the ripening period. The effects of three such PGRs—ethephon, abscisic acid, and methyl jasmonate—on fruit ripening were evaluated in the rabbiteye blueberry (Vaccinium virgatum) cultivars ‘Premier’ and ‘Powderblue’. Application of ethephon, an ethylene-releasing PGR, at 250 mg L−1 when 30–40% of fruit on the plant were ripe, accelerated ripening by increasing the proportion of blue (ripe) fruit by 1.5–1.8-fold within 4 to 7 days after treatment in both cultivars. Ethephon applications did not generally alter fruit quality characteristics at harvest or during postharvest storage, except for a slight decrease in juice pH at 1 day of postharvest storage and an increase in fruit firmness and titratable acidity after 15 days of postharvest storage in Powderblue. In Premier, ethephon applications decreased the proportion of defective fruit at 29 days of postharvest storage. Abscisic acid (600–1000 mg L−1) and methyl jasmonate (0.5–1 mM) applications did not alter the proportion of ripe fruit in either cultivar. These applications also had little effect on fruit quality characteristics at harvest and during postharvest storage. None of the above PGR applications affected the development of naturally occurring postharvest pathogens during storage. Together, data from this study indicated that ethephon has the potential to accelerate ripening in rabbiteye blueberry fruit, allowing for a potential decrease in the number of fruit harvests.

Evaluation of Borage Extracts As Potential Biostimulant Using a Phenomic, Agronomic, Physiological, and Biochemical Approach

Biostimulants are substances able to improve water and nutrient use efficiency and counteract stress factors by enhancing primary and secondary metabolism. Premise of the work was to exploit raw extracts from leaves (LE) or flowers (FE) of Borago officinalis L., to enhance yield and quality of Lactuca sativa 'Longifolia,' and to set up a protocol to assess their effects. To this aim, an integrated study on agronomic, physiological and biochemical aspects, including also a phenomic approach, has been adopted. Extracts were diluted to 1 or 10 mL L-1, sprayed onto lettuce plants at the middle of the growing cycle and 1 day before harvest. Control plants were treated with water. Non-destructive analyses were conducted to assess the effect of extracts on biomass with an innovative imaging technique, and on leaf photosynthetic efficiency (chlorophyll a fluorescence and leaf gas exchanges). At harvest, the levels of ethylene, photosynthetic pigments, nitrate, and primary (sucrose and total sugars) and secondary (total phenols and flavonoids) metabolites, including the activity and levels of phenylalanine ammonia lyase (PAL) were assessed. Moreover, a preliminary study of the effects during postharvest was performed. Borage extracts enhanced the primary metabolism by increasing leaf pigments and photosynthetic activity. Plant fresh weight increased upon treatments with 10 mL L-1 doses, as correctly estimated by multi-view angles images. Chlorophyll a fluorescence data showed that FEs were able to increase the number of active reaction centers per cross section; a similar trend was observed for the performance index. Ethylene was three-fold lower in FEs treatments. Nitrate and sugar levels did not change in response to the different treatments. Total flavonoids and phenols, as well as the total protein levels, the in vitro PAL specific activity, and the levels of PAL-like polypeptides were increased by all borage extracts, with particular regard to FEs. FEs also proved efficient in preventing degradation and inducing an increase in photosynthetic pigments during storage. In conclusion, borage extracts, with particular regard to the flower ones, appear to indeed exert biostimulant effects on lettuce; future work will be required to further investigate on their efficacy in different conditions and/or species.

VcBBX, VcMYB21, and VcR2R3MYB Transcription Factors Are Involved in UV-B-Induced Anthocyanin Biosynthesis in the Peel of Harvested Blueberry Fruit

This study was carried out to better understand the mechanism responsible for increasing the anthocyanins in blueberries after UV-B radiation at 6.0 kJ m^-2 for 20 min. UV-B induced upregulation of genes involved in anthocyanin biosynthesis in blueberry fruit compared to a nontreated control. Phenylalanine ammonia lyase, chalcone synthase, and flavanone 3'-hydroxylase, which are enzymes that function upstream of anthocyanin biosynthesis, were significantly expressed by UV-B. Expression levels of VcBBX, VcMYB21, and VcR2R3MYB transcription factors (TFs) were upregulated by UV-B in the same manner as the anthocyanin biosynthesis genes. The significant increase in the expression of TFs occurred immediately after UV-B treatment and was then maximized within 3 h. In accordance with these changes, individual anthocyanin contents in the fruits treated with UV-B significantly increased within 6 h and were 2-3-fold higher than the control. Our results indicated that UV-B radiation stimulates an increase in anthocyanin biosynthesis, which could be upregulated by the TFs studied.

Differential Gene Expression Analysis in Polygonum minus Leaf upon 24 h of Methyl Jasmonate Elicitation

Polygonum minus is an herbal plant that grows in Southeast Asian countries and traditionally used as medicine. This plant produces diverse secondary metabolites such as phenolic compounds and their derivatives, which are known to have roles in plant abiotic and biotic stress responses. Methyl jasmonate (MeJA) is a plant signaling molecule that triggers transcriptional reprogramming in secondary metabolism and activation of defense responses against many biotic and abiotic stresses. However, the effect of MeJA elicitation on the genome-wide expression profile in the leaf tissue of P. minus has not been well-studied due to the limited genetic information. Hence, we performed Illumina paired-end RNA-seq for de novo reconstruction of P. minus leaf transcriptome to identify differentially expressed genes (DEGs) in response to MeJA elicitation. A total of 182,111 unique transcripts (UTs) were obtained by de novo assembly of 191.57 million paired-end clean reads using Trinity analysis pipeline. A total of 2374 UTs were identified to be significantly up-/down-regulated 24 h after MeJA treatment. These UTs comprising many genes related to plant secondary metabolite biosynthesis, defense and stress responses. To validate our sequencing results, we analyzed the expression of 21 selected DEGs by quantitative real-time PCR and found a good correlation between the two analyses. The single time-point analysis in this work not only provides a useful genomic resource for P. minus but also gives insights on molecular mechanisms of stress responses in P. minus.

The Combined Effects of Ethylene and MeJA on Metabolic Profiling of Phenolic Compounds in Catharanthus roseus Revealed by Metabolomics Analysis

Phenolic compounds belong to a class of secondary metabolites and are implicated in a wide range of responsive mechanisms in plants triggered by both biotic and abiotic elicitors. In this study, we approached the combinational effects of ethylene and MeJA (methyl jasmonate) on phenolic compounds profiles and gene expressions in the medicinal plant Catharanthus roseus. In virtue of a widely non-targeted metabolomics method, we identified a total of 34 kinds of phenolic compounds in the leaves, composed by 7 C6C1-, 11 C6C3-, and 16 C6C3C6 compounds. In addition, 7 kinds of intermediates critical for the biosynthesis of phenolic compounds and alkaloids were identified and discussed with phenolic metabolism. The combinational actions of ethylene and MeJA effectively promoted the total phenolic compounds, especially the C6C1 compounds (such as salicylic acid, benzoic acid) and C6C3 ones (such as cinnamic acid, sinapic acid). In contrast, the C6C3C6 compounds displayed a notably inhibitory trend in this case. Subsequently, the gene-to-metabolite networks were drawn up by searching for correlations between the expression profiles of 5 gene tags and the accumulation profiles of 41 metabolite peaks. Generally, we provide an insight into the controlling mode of ethylene-MeJA combination on phenolic metabolism in C. roseus leaves.