Cinnamate 4-hydroxylase Research Articles

Enhancing biomass and productivity of coumarins and essential oil in ajwain (Trachyspermum ammi) sprouts via laser light treatment

Ajwain, Trachyspermum (T.) ammi, is a coumarin-rich, highly nutritive, and medicinally important herb, however, there is not enough data on the efficiency of laser irradiation in inducing such properties. Herein, the effect of seed treatment with laser irradiations [helium-neon (He-Ne, 632 nm, 5 mW) and helium-cadmium (He-Cd, 460 nm, 16.2 mW)] at 500 mJ energy for 5 min on the biomass, photosynthesis, and the metabolism of coumarins, essential oil, and their precursor metabolites in two varieties of ajwain sprouts i.e., Desi and Chakwal was investigated for the first time. Laser irradiation increased sprout biomass accumulation by improving photosynthesis, chlorophyll content, and respiration. Additionally, laser treatment enhanced the metabolism of coumarins and essential oil, which was explained by the increased availability of their precursors (phenylalanine, cinnamic acid, and shikimic acid). There were also increases in the activity of the key enzymes involved in the biogenesis of phenylpropanoid and coumarins, i.e., 3-Deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHPS), cinnamate-4-hydroxylase (C4H), 4-coumarate: coenzyme A ligase (4CL), and p-coumarate 3-hydroxylase (C3H). Furthermore, laser treatment induced the accumulation of total and individual phenolics and flavonoids. Consequently, laser treatment significantly improved the antibacterial properties of ajwain sprouts against four foodborne pathogens included Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, and Salmonella spp. Ajwain variety-specific responses to laser light treatment confirmed by principal component analysis (PCA) showed that Desi variety was more responsive. The efficiency of He-Ne was greater than He-Cd laser, which suggests He-Ne laser treatment as a promising approach to boost the production of valuable pigments, coumarins, and essential oils in ajwain sprouts.

Integrated transcriptomic and metabolomic analysis provides insight into the regulation of leaf senescence in rice

Leaf senescence is one of the most precisely modulated developmental process and affects various agronomic traits of rice. Anti-senescence rice varieties are important for breeding application. However, little is known about the mechanisms underlying the metabolic regulatory process of leaf senescence in rice. In this study, we performed transcriptomic and metabolomic analyses of the flag leaves in Yuenong Simiao (YN) and YB, two indica rice cultivars that differ in terms of their leaf senescence. We found 8524 genes/204 metabolites were differentially expressed/accumulated in YN at 30 days after flowering (DAF) compared to 0 DAF, and 8799 genes/205 metabolites were differentially expressed in YB at 30 DAF compared to 0 DAF. Integrative analyses showed that a set of genes and metabolites involved in flavonoid pathway were significantly enriched. We identified that relative accumulation of PHENYLALANINE AMMONIA-LYASE (PAL), CINNAMATE 4-HYDROXYLASE (C4H), 4-COUMAROYL-COA LIGASE (4CL), CHALCONE SYNTHASE (CHS) and CHALCONE ISOMERASE (CHI) in YN30/0 was higher than that in YB30/0. Three flavonoid derivatives, including phloretin, luteolin and eriodictyol, showed lower abundances in YB than in YN at 30 DAF. We further revealed a MYB transcription factor, which is encoded by OsR498G0101613100 gene, could suppress the expression of CHI and CHS. Our results suggested a comprehensive analysis of leaf senescence in a view of transcriptome and metabolome and would contribute to exploring the molecular mechanism of leaf senescence in rice.

Ethanol treatment suppresses the yellowing of fresh-cut yam by repressing the phenylpropanoid pathway and bisdemethoxycurcumin biosynthesis

An ethanol treatment (10 % v/v) inhibited the yellowing of fresh-cut yam during storage. The ethanol treatment also prevented bisdemethoxycurcumin formation, and reduced the contents of metabolites in fresh-cut yam during storage at 25 °C. Ethanol treatment also inhibited the activities of key enzymes in the phenylpropanoid pathway, including phenylalanine ammonia lyase (PAL), cinnamic acid-4-hydroxylase (C4H), and 4-coumarate-CoA ligase (4CL), and decreased the transcription level expressions of PAL, C4H, and 4CL compared to the control. The expressions of diketide-CoA synthase, curcumin synthase 3, and curcumin synthase were also reduced by ethanol treatment compared to the control, in agreement with the absence of bisdemethoxycurcumin in fresh-cut yam treated with ethanol. These findings suggest that ethanol can be used to attenuate the yellowing of fresh-cut yam stored at 25 °C, which may be related to ethanol inhibition of the phenylpropanoid pathway and bisdemethoxycurcumin biosynthesis.

Ascorbic acid treatment inhibits wound healing of fresh-cut potato strips by controlling phenylpropanoid metabolism

In this study, we investigated the ability of ascorbic acid (AA) to regulate the wound-healing response in fresh-cut potato strips during storage. The results demonstrated that treatments of AA could delay browning, decrease hardening, improve taste, as well as reduce weight loss and respiration rate. Furthermore, AA treatment inhibited wound healing by modulating the activity of phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), 4-coumarate-CoA ligase (4CL), chalcone synthase (CHS) and coumarate-3-hydroxylase (C3H), increasing total phenolics and flavonoid content, and decreasing monomeric phenolic acid content, including caffeic acid, p-coumaric acid, and ferulic acid. The accumulation of lignin and the polyphenolic component of suberin was also reduced. Overall, our results provided information on wound healing and revealed the potential benefits of AA in regulating the process of suberization in potato strips.

GABA Regulates Phenolics Accumulation in Soybean Sprouts under NaCl Stress.

NaCl stress causes oxidative stress in plants; γ-aminobutyric acid (GABA) could alleviate such abiotic stress by enhancing the synthesis of phenolics, but the underlying mechanism is not clear. We investigated the effects of GABA on phenolics accumulation in soybean sprouts under NaCl stress by measuring changes in the content of physiological biochemicals and phenolic substances, in the activity and gene expression of key enzymes, and in antioxidant capacity. GABA reduced the oxidative damage in soybean sprouts caused by NaCl stress and enhanced the content of total phenolics, phenolic acids, and isoflavones by 16.58%, 22.47%, and 3.75%, respectively. It also increased the activities and expression of phenylalanine ammonia lyase, cinnamic acid 4-hydroxylase, and 4-coumarate coenzyme A ligase. Furthermore, GABA increased the activity of antioxidant enzymes and the antioxidant capacity. These events were inhibited by 3-mercaptopropionate (an inhibitor for GABA synthesis), indicating that GABA mediated phenolics accumulation and antioxidant system enhancement in soybean sprouts under NaCl stress.

The phenylpropanoid pathway inhibitor piperonylic acid induces broad-spectrum pest and disease resistance in plants.

Although many phenylpropanoid pathway-derived molecules act as physical and chemical barriers to pests and pathogens, comparatively little is known about their role in regulating plant immunity. To explore this research field, we transiently perturbed the phenylpropanoid pathway through application of the CINNAMIC ACID-4-HYDROXYLASE (C4H) inhibitor piperonylic acid (PA). Using bioassays involving diverse pests and pathogens, we show that transient C4H inhibition triggers systemic, broad-spectrum resistance in higher plants without affecting growth. PA treatment enhances tomato (Solanum lycopersicum) resistance in field and laboratory conditions, thereby illustrating the potential of phenylpropanoid pathway perturbation in crop protection. At the molecular level, transcriptome and metabolome analyses reveal that transient C4H inhibition in tomato reprograms phenylpropanoid and flavonoid metabolism, systemically induces immune signalling and pathogenesis-related genes, and locally affects reactive oxygen species metabolism. Furthermore, C4H inhibition primes cell wall modification and phenolic compound accumulation in response to root-knot nematode infection. Although PA treatment induces local accumulation of the phytohormone salicylic acid, the PA resistance phenotype is preserved in tomato plants expressing the salicylic acid-degrading NahG construct. Together, our results demonstrate that transient phenylpropanoid pathway perturbation is a conserved inducer of plant resistance and thus highlight the crucial regulatory role of this pathway in plant immunity.

English

Procyanidins (PAs) is the important flavonoids components in strawberry young fruits, whichis synthesizedthrough direct polymerizationof flavanone-3-ol units. Numerous studies have beendone on the synthesis of PAs, while the oxidation/polymerization processes have not been fully explored. AtTT10, a laccasel-like polyphenol oxidase,was recently reported to be participated in the oxidative polymerization of proanthocyanidins. Whether FaTT10hasapositiveeffect onoxidative polymerization of strawberry fruit PAsis unclear. In this study, FaTT10 in strawberries were isolated and analyzed. Transient overexpression of FaTT10 decreased the accumulation of PAs monomer in strawberry fruit,whereas RNA interference increased the level of anthocyanin and PAs monomer. 4-Dimethylaminocinamaldehyde (DMACA)staining results also showed that lighter blue color in the FaTT10-RNAi fruit and concentrated blue color in the FaTT10-overexpression fruit. Meanwhile, PAs monomer showed a drop-and-rise tendency during strawberry fruit development and ripening.Furthermore, the expression of several flavonoids metabolism-related geneswere affected by the altered FaTT10 gene expression levels, such as L-phenylalanine ammonia-lyase(PAL); dihydroflavonol reductase(DFR);chalcone isomerase(CHI); flavanone 3-hydroxylase(F3H); 4-coumarate:CoA ligase(4CL); Cinnamate 4-hydroxylase(C4H); chalcone synthase(CHS); anthocyanin reductase(ANR); lecoanthocyanidins reductase(LAR) andanthocyanin synthase(ANS). In conclusion, these results revealed that FaTT10 is specifically involved in oxidative polymerization of PAsby regulating the expression of flavonoids metabolism-related genes in strawberry fruits. © 2021 Friends Science Publishers

Ca<SUP>2+</SUP> and ABA on the Accumulation of GABA and Flavonoids in Germinated <i>Salicornia bigelovii </i>Torr. under NaCl Stress

The effects of CaCl2 and abscisic acid (ABA) on the sprouts growth, γ-aminobutyric acid (GABA) and flavonoids accumulation in germinated Salicornia bigelovii Torr. were investigated under NaCl stress. Results showed that the content of GABA and flavonoids increased by 1.20 and 1.19 times under 5 mM CaCl2 treatment compared with the control group. The key enzymes including glutamate decarboxylase (GAD) and diamine oxidase (DAO), phenylalanine ammonolyses (PAL), cinnamicacid-4-hydroxylase (C4H) and 4-coumarate: CoA ligase (4CL) were increased significantly (p-1 NaCl, S. bigelovii had the higher content of GABA (398.26 mg100g-1) and flavonoids (36.90 mgg-1) than control group (pS. bigelovii.

Effects of 5-aminolevulinic acid on Anthocyanin synthesis in Vitis Vinifera ‘Crimson Seedless’ grapes at the transcriptomics level

ABSTRACT In order to study the effect of exogenous 5-aminolevulinic acid (ALA) on the expression of genes associated with anthocyanin biosynthesis in the transcriptome of ‘Crimson Seedless’ grape (Vitis vinifera) peel, sequencing technology was used to compare the transcriptomes from water and ALA treated ‘Crimson Seedless’ grapes. Transcriptome sequencing was performed at two periods (d5 and d15) after peel treatment. The enrichment analysis of the Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathways indicated that the metabolic pathways induced by exposure to ALA were mainly the phenylpropanoid biosynthesis, flavonoid biosynthesis, anthocyanin biosynthesis, phenylalanine metabolism, and plant hormone signal transduction pathways. In the anthocyanin synthesis pathway, ALA treatment appeared to mainly regulate the phenylalanine ammonia-lyase, cinnamate 4-hydroxylase and chalcone synthase genes in the upstream pathway of anthocyanin synthesis, and the dihydroflavonol-4-reductase gene in the downstream pathway, with the effect being most obvious at d5.This study reveals the mechanism by which exogenous ALA promotes anthocyanin synthesis at the molecular level, and lays the foundation for further study of the physiological role of ALA.

Postharvest temperature and light treatments induce anthocyanin accumulation in peel of ‘Akihime’ plum (Prunus salicina Lindl.) via transcription factor PsMYB10.1

Anthocyanin accumulation is responsible for red pigmentation in plum peel and affected by light and temperature. We investigated the effects of temperature and LED light (400−800 nm, with following red: green: blue ratio 20.9: 75.7: 3.4 respectively) with total radiant flux adjusted at 150 mol m−2 s−1 on anthocyanin accumulation in postharvest ‘Akihime’ plum peel and found that 20 °C/light could induce anthocyanin concentration and therefore improve red coloration. However, no significant anthocyanin accumulation was detected in the peel of plums treated with 30 °C or under dark conditions. RNA-Seq and qRT-PCR analysis showed that the transcript levels of anthocyanin accumulation-related genes, including phenylalanine ammonialyase (PAL), cinnamate-4-hydroxylase (C4H), 4-coumaroyl:CoA-ligase (4CL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS), UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT) and glutathione S-transferase (GST) in the peel were upregulated by 20 °C/light treatment. Transcription factors differentially regulated by temperature and light were identified. A homolog of peach anthocyanin MYB activator, namely PsMYB10.1, was lowly expressed in the peel of unpigmented fruit but significantly upregulated by 20 °C/light treatment. The function of PsMYB10.1 was verified by transient overexpression in Nicotiana tabacum leaves, resulting in strong anthocyanin accumulation when co-infiltrated with PsbHLH3. Dual luciferase assays further showed that PsMYB10.1 activated the promoters of the anthocyanin biosynthetic genes PsANS, PsUFGT and PsGST. These results suggest that appropriate temperature and light regimes at postharvest can induce anthocyanin accumulation in the peel of ‘Akihime’ plum by activating the expression of the positive regulator PsMYB10.1 and consequently the genes involved in biosynthesis and transportation of anthocyanin.

Transcriptomic analysis for differential expression of genes involved in secondary metabolite production in Narcissus pseudonarcissus field derived bulb and in vitro callus

The Amaryllidaceae genus Narcissus contains diversified secondary metabolites, which are important sources of biologically active alkaloids. The biochemical pathways for secondary metabolite production require primary metabolites to undergo a series of modifications catalyzed by several enzymes but the knowledge on their biosynthesis is very limited. This study is undertaken to reveal the differential expression of transcripts related to secondary metabolites biosynthesis in Narcissus basal plate and in vitro callus.RNA-seq analysis of Narcissus basal plate (field) and in vitro callus ensued total 2153 differentially expressed transcripts and 83.46 % of those were annotated. The largest gene group was designated as uncharacterized proteins (10.24 %) and the second largest group was genes responsible for secondary metabolite production (8.88 %). The genes involved in the biosynthesis of alkaloids; cytochrome P450s, O-methyltransferases (OMTs), NADP/NADPH dehydrogenases or reductases, SAM-synthetases or decarboxylases, 3-ketoacyl-CoA, acyl-CoA, cinnamoyl-CoA, cinnamate 4-hydroxylase, alcohol dehydrogenase, caffeic acid, N-methyltransferase, and NADPH-cytochrome P450s were present in both basal plate and callus. However, cytochrome P450s, and OMTs which are responsible for regulating the later stage of alkaloids biosynthesis were mainly up-regulated in field samples. Whereas, the enzymes involved in initial biosynthetic pathways, fructose biphosphate adolase (FBA), aminotransferases, dehydrogenases, hydroxyl methyl glutarate (HMT), and glutamate synthase (GS) leading to the biosynthesis of precursors of secondary metabolites; tyrosine, phenylalanine, and tryptophan were up-regulated in callus. Furthermore, Gene Ontology (GO) annotation of the transcripts and associated Kyoto Encyclopedia of Genes and Genomes (KEGG) and Plant Reactome pathway maps were postulated. This knowledge on probable genes or enzymes involved in secondary metabolism, their networking pathway and molecular regulation in field and in vitro callus would provide a deep insight into the Narcissus plant biology related to valuable metabolite production.

β-Aminobutyric acid treatment accelerates the deposition of suberin polyphenolic and lignin at wound sites of potato tubers during healing

β-Aminobutyric acid (BABA) is a nonprotein amino acid that induces plant defense responses to numerous biotic and abiotic stresses. However, whether BABA treatment affects the wound healing process of potato tubers has yet to be reported. In this study, we examined the effects of BABA treatment on the weight loss and disease index of Solanum tuberosum L. cv. Atlantic potato tubers inoculated with Fusarium sulphureum and assessed the deposition of suberin polyphenolic (SPP) and lignin at the wound sites of these tubers during healing. We also investigated the indexes involved in phenylpropane metabolism, H2O2, and peroxidase in the underlying effect mechanism. BABA treatment effectively reduced the weight loss of wounded tubers (by 41.0 %) and the disease index of inoculated tubers (by 43.2 %) during healing (at 21 d and relative to the control). BABA treatment also accelerated the deposition of SPP and lignin at wound sites. SPP and lignin cell layers in the treated tubers were 58.45 % and 54.72 % thicker, respectively, than the equivalent cell layers in the controls at 7 d of healing. Additionally, BABA treatment significantly enhanced the activities of phenylalanine ammonia-lyase (PAL), 4-coumaryl coenzyme A ligase (4CL), cinnamic acid-4-hydroxylase (C4H), and cinnamyl alcohol dehydrogenase (CAD) while also promoting the synthesis of cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid, sinapic acid, cinnamyl alcohol, coniferyl alcohol, and sinapyl alcohol, as well as increasing total phenolic and lignin content, at wound sites during healing. Furthermore, BABA treatment increased H2O2 content and peroxidase activity at the wounds. These results suggest that BABA treatment activates phenylpropanoid metabolism, increases H2O2 content and peroxidase activity, and accelerates the deposition of SPP and lignin in potato tuber wounds, all of which lead to reductions in the weight loss and disease index of tubers during healing.

Nitrogen deficiency maintains the yield and improves the antioxidant activity of Coreopsis tinctoria Nutt.

Nitrogen (N) deficiency levels were investigated for their potential to maintain the yield and improve antioxidant activity of Coreopsis tinctoria. Inflorescences and leaves at 0, 10, 20, 30, 40, and 50 d after flowering were frozen at -80 °C and plant growth, antioxidant activity, bioactive substance, enzyme activity, and gene expression were evaluated. N deficiency maintained the total number of flowers, promoted phenol and flavonoid accumulation, and enhanced antioxidant activity. Moreover, N deficiency stimulated activities of phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H) and 4-coumarate:coenzyme A ligase (4CL), and induced CtPAL, CtC4H and Ct4CL gene expression. The data also suggest that N-deficiency-induced phenolic and flavonoid accumulation occurs due to the activation of biosynthetic pathways in C. tinctoria. We characterize the unique features of C. tinctoria under N-deficiency conditions and provide valuable information for the cultivation of high-N use efficiency varieties with low input and high output.

Seedling developmental defects upon blocking CINNAMATE-4-HYDROXYLASE are caused by perturbations in auxin transport.

The phenylpropanoid pathway serves a central role in plant metabolism, providing numerous compounds involved in diverse physiological processes. Most carbon entering the pathway is incorporated into lignin. Although several phenylpropanoid pathway mutants show seedling growth arrest, the role for lignin in seedling growth and development is unexplored. We use complementary pharmacological and genetic approaches to block CINNAMATE-4-HYDROXYLASE (C4H) functionality in Arabidopsis seedlings and a set of molecular and biochemical techniques to investigate the underlying phenotypes. Blocking C4H resulted in reduced lateral rooting and increased adventitious rooting apically in the hypocotyl. These phenotypes coincided with an inhibition in AUX transport. The upstream accumulation in cis-cinnamic acid was found to be likely to cause polar AUX transport inhibition. Conversely, a downstream depletion in lignin perturbed phloem-mediated AUX transport. Restoring lignin deposition effectively reestablished phloem transport and, accordingly, AUX homeostasis. Our results show that the accumulation of bioactive intermediates and depletion in lignin jointly cause the aberrant phenotypes upon blocking C4H, and demonstrate that proper deposition of lignin is essential for the establishment of AUX distribution in seedlings. Our data position the phenylpropanoid pathway and lignin in a new physiological framework, consolidating their importance in plant growth and development.

BTH Treatment Delays the Senescence of Postharvest Pitaya Fruit in Relation to Enhancing Antioxidant System and Phenylpropanoid Pathway.

The plant resistance elicitor Benzo (1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) can enhance disease resistance of harvested fruit. Nonetheless, it is still unknown whether BTH plays a role in regulating fruit senescence. In this study, exogenous BTH treatment efficiently delayed the senescence of postharvest pitaya fruit with lower lipid peroxidation level. Furthermore, BTH-treated fruit exhibited lower hydrogen peroxide (H2O2) content, higher contents of reduced ascorbic acid (AsA) and reduced glutathione (GSH) levels and higher ratios of reduced to oxidized glutathione (GSH/GSSG) and ascorbic acid (AsA/DHA), as well as higher activities of ROS scavenging enzymes, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD) and glutathione reductase (GR) in comparison with control fruit. Moreover, BTH treatment enhanced the activities of phenylpropanoid pathway-related enzymes, including cinnamate-4-hydroxylase (C4H), phenylalanine ammonia-lyase (PAL) and 4-coumarate/coenzyme A ligase (4CL) and the levels of phenolics, flavonoids and lignin. In addition, BTH treatment upregulated the expression of HuSOD1/3/4, HuCAT2, HuAPX1/2 and HuPOD1/2/4 genes. These results suggested that application of BTH delayed the senescence of harvested pitaya fruit in relation to enhanced antioxidant system and phenylpropanoid pathway.

Effects of nitric oxide on the alleviation of postharvest disease induced by Penicillium italicum in navel orange fruits

SummaryThe present study evaluated the effects of 15 μL L‐1 nitric oxide (NO) on the fruit defence response of ‘Newhall’ navel orange. The decay rate of NO‐treated navel orange fruits was significantly lower than that of control fruits during storage at 20 °C storage (P < 0.05). Treatment with NO suppressed the increase in disease incidence and lesion area in orange fruits inoculated with Penicillium italicum (P. italicum); significantly increased the activities of phenolic metabolism‐associated enzymes and pathogenesis‐related (PR) proteins, including polyphenoloxidase (PPO), phenylalanine ammonia‐lyase (PAL), β‐1,3‐glucanase (GLU) and chitinase (CHT); and enhanced the activities of key enzymes, including 4‐coumarate: CoA ligase (4CL), cinnamate‐4‐hydroxylase (C4H) and chalcone isomerase (CHI) in the phenylpropanoid pathway. The contents of total phenolics, flavonoids and lignin were also higher in NO‐treated fruits than in control fruits. The findings suggest that exogenous NO could induce disease resistance against P. italicum in navel orange fruits.

Pichia galeiformis Induces Resistance in Postharvest Citrus by Activating the Phenylpropanoid Biosynthesis Pathway.

This study aimed to investigate the effect of Pichia galeiformis on disease resistance and elucidate the changes in phenylpropane biosynthesis treated by P. galeiformis in postharvest citrus. The results showed that P. galeiformis reduced the disease incidence and lesion diameters without direct contact with the pathogen Penicillium digitatum. Transcriptome analysis revealed that phenylpropanoid biosynthesis was triggered by P. galeiformis. Genes encoding phenylpropanoid biosynthesis were upregulated, including phenylalanine ammonia-lyase (PAL), 4-coumaroyl-CoA ligase (4CL), cinnamate-4-hydroxylase (C4H), peroxidase (POD), cinnamyl alcohol dehydrogenase (CAD), O-methyltransferase, and hydroxyl cinnamoyl transferase. Moreover, P. galeiformis increased the activity of PAL, 4CL, C4H, POD, polyphenol oxidase, and CAD in citrus pericarp. In addition, P. galeiformis treated citrus displayed higher levels of total phenolic compounds, flavonoid, and lignin and higher amounts of ferulic and sinapic acid. In conclusion, these results suggested that P. galeiformis could induce resistance through modulating the pathway of phenylpropanoid biosynthesis in postharvest citrus.

Spatio-temporal control of phenylpropanoid biosynthesis by inducible complementation of a cinnamate 4-hydroxylase mutant.

Cinnamate 4-hydroxylase (C4H) is a cytochrome P450-dependent monooxygenase that catalyzes the second step of the general phenylpropanoid pathway. Arabidopsis reduced epidermal fluorescence 3 (ref3) mutants, which carry hypomorphic mutations in C4H, exhibit global alterations in phenylpropanoid biosynthesis and have developmental abnormalities including dwarfing. Here we report the characterization of a conditional Arabidopsis C4H line (ref3-2pOpC4H), in which wild-type C4H is expressed in the ref3-2 background. Expression of C4H in plants with well-developed primary inflorescence stems resulted in restoration of fertility and the production of substantial amounts of lignin, revealing that the developmental window for lignification is remarkably plastic. Following induction of C4H expression in ref3-2pOpC4H, we observed rapid and significant reductions in the levels of numerous metabolites, including several benzoyl and cinnamoyl esters and amino acid conjugates. These atypical conjugates were quickly replaced with their sinapoylated equivalents, suggesting that phenolic esters are subjected to substantial amounts of turnover in wild-type plants. Furthermore, using localized application of dexamethasone to ref3-2pOpC4H, we show that phenylpropanoids are not transported appreciably from their site of synthesis. Finally, we identified a defective Casparian strip diffusion barrier in the ref3-2 mutant root endodermis, which is restored by induction of C4H expression.

Postharvest UV-C irradiation increased the flavonoids and anthocyanins accumulation, phenylpropanoid pathway gene expression, and antioxidant activity in sweet cherries (Prunus avium L.)

Ultraviolet (UV) influences postharvest changes in secondary metabolites of fruit. In this study, sweet cherries were treated with UV-C irradiation (1.05, 2.10, and 4.20 kJ/m2) for different treatment periods, they were stored at room temperature (25.0 ± 2.0 ℃) for 6 days. The results showed that the total phenolics, flavonoids, and anthocyanins increased in response to UV-C during storage. UPLC-ESI-MS analysis indicated that the individual flavonoids and anthocyanins contents increased, including cyanidin 3-O-galactoside, cyanidin O-syringic acid, cyanidin 3-O-glucoside, pelargonidin 3-O-glucoside, tricin 5-O-hexoside, luteolin C-hexoside, Di-O-methylquercetin, and naringenin-7-O-glucoside. Furthermore, UV-C (2.10 kJ/m2) treatment upregulated the enzymes activity and genes expression of phenylpropanoid pathway. Highly significant correlations were found among flavonoids, anthocyanins, phenylalanine ammonia lyase (PAL) and genes expression of ANS, DFR, UFGT (r > 0.6, p < 0.01) and cinnamate 4-hydroxylase (C4H) and PAL, C4H, 4CL, CHI, ANS, DFR expressions (r> 0.6, p < 0.01). These results contribute to illustrating the molecular mechanism of flavonoids and anthocyanins biosynthesis under the UV-C irradiation in sweet cherries and promote the development of postharvest in agriculture.

Methyl jasmonate promotes wound healing by activation of phenylpropanoid metabolism in harvested kiwifruit

A rapid wound healing in vegetables and fruit is instrumental in maintaining fruit quality and extension of shelf life. In this study, wounded kiwifruit were separately treated with methyl jasmonate (MeJA) and diethyldithiocarbamic acid (DIECA, an inhibitor of jasmonate biosynthesis) to evaluate the effect of MeJA on wound healing of kiwifruit. The results showed that MeJA treatment leads to increases of endogenous JA biosynthesis, lipoxygenase (LOX) and 12-oxo-phytodienoic acid reductase (OPR) activities, and JA synthesis genes expression, while DIECA represses these processes. Meanwhile, MeJA promoted the autofluorescence of suberin polyphenolic (SPP) and the accumulation of SPP monomers. MeJA-treated group demonstrated significantly enhanced total phenols, flavonoids, and lignin contents. Besides, MeJA promoted the activities of phenylalanine ammonia-lyase (PAL), cinnamic acid-4-hydroxylase (C4H), 4-COumaric-COA ligase (4CL), peroxidase (POD), polyphenol oxidase (PPO), and the respective gene expression levels. Results suggest that wound healing in kiwifruit could be promoted by MeJA via activation of phenylpropanoid metabolism.