Cinnamate 4-hydroxylase Research Articles

Effects of Exogenous Nitric Oxide Treatment on Grape Berries Against Botrytis cinerea and Alternaria alternata Related Enzymes and Metabolites.

Postharvest losses of grape berries caused by the pathogenic fungi Botrytis cinerea and Alternaria alternata have been widely reported, and nitric oxide (NO) as a plant signaling molecule to control postharvest diseases has recently become an active research topic. This study aimed to investigate the regulatory effect of NO on the interaction between grape berries and fungi. During interactions between grape berries and pathogenic fungi, treatment with 10 mM sodium nitroprusside (SNP, an NO donor) delayed the decline of the physiological quality of the grape berries and had positive effects on the weight loss rate, firmness, and respiration intensity. SNP treatment increased the activities of superoxide dismutase (SOD) and polyphenol oxidase (PPO) and inhibited the activities of peroxidase (POD) and catalase (CAT) of grape berries during the resistance to fungal pathogen infection. In addition, the increase in browning degree and the accumulation of hydrogen peroxide were inhibited by SNP treatment. In the phenylpropane metabolic pathway, the activities of phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), and 4-coumaric acid coenzyme A ligase (4CL) were increased during the activation of grape berries during the resistance to pathogen infection by SNP, and the intermediate metabolites lignin, flavonoids, and total phenols were accumulated. In addition, SNP treatment had a regulatory effect on the gene expression levels of SOD, POD, PPO, PAL, and 4CL. These results suggested that SNP treatment was effective for the preservation and disease reduction of grape berries.

Non-specific effects of the CINNAMATE-4-HYDROXYLASE inhibitor piperonylic acid.

Chemical inhibitors are often implemented for the functional characterization of genes to overcome the limitations associated with genetic approaches. Although it is well established that the specificity of the compound is key to success of a pharmacological approach, off-target effects are often overlooked or simply neglected in a complex biological setting. Here we illustrate the cause and implications of such secondary effects by focusing on piperonylic acid (PA), an inhibitor of CINNAMATE-4-HYDROXYLASE (C4H) that is frequently used to investigate the involvement of lignin during plant growth and development. When supplied to plants, we found that PA is recognized as a substrate by GRETCHEN HAGEN 3.6 (GH3.6), an amido synthetase involved in the formation of the indole-3-acetic acid (IAA) conjugate IAA-Asp. By competing for the same enzyme, PA interferes with IAA conjugation, resulting in an increase in IAA concentrations in the plant. In line with the broad substrate specificity of the GH3 family of enzymes, treatment with PA increased not only IAA levels but also those of other GH3-conjugated phytohormones, namely jasmonic acid and salicylic acid. Finally, we found that interference with the endogenous function of GH3s potentially contributes to phenotypes previously observed upon PA treatment. We conclude that deregulation of phytohormone homeostasis by surrogate occupation of the conjugation machinery in the plant is likely a general phenomenon when using chemical inhibitors. Our results hereby provide a novel and important basis for future reference in studies using chemical inhibitors.

Chitooligosaccharide accelerated wound healing in potato tubers by promoting the deposition of suberin polyphenols and lignin at wounds

Chitooligosaccharide (COS) is a low molecular weight product of chitosan degradation. Although COS induces plant resistance by activating phenylpropanoid metabolism, there are few reports on whether COS accelerates wound healing in potato tubers by promoting the deposition of phenolic acids and lignin monomers at wounds. The results showed that COS activated phenylalanine ammonialyase and cinnamate 4-hydroxylase and promoted the synthesis of cinnamic, caffeic, p-coumaric, ferulic acids, total phenolics and flavonoids. COS activated 4-coumaric acid coenzyme A ligase and cinnamyl alcohol dehydrogenase and promoted the synthesis of sinapyl, coniferyl and cinnamyl alcohols. COS also increased H2O2 levels and peroxidase activity and accelerated the deposition of suberin polyphenols and lignin on wounds. In addition, COS reduced weight loss and inhibited lesion expansion in tubers inoculated with Fusarium sulfureum. Taken together, COS accelerated wound healing in potato tubers by inducing phenylpropanoid metabolism and accelerating the deposition of suberin polyphenols and lignin at wounds.

UV-B radiation enhances isoflavone accumulation and antioxidant capacity of soybean calluses.

Isoflavones are a class of flavonoids that belong to a large family of polyphenols and synthesized predominantly in legume, and they play important roles including acting as antioxidant, preventing osteoporosis, reducing the risk of atherosclerosis, and protecting against cardiovascular disease. This study focused on the accumulation and synthetic metabolism of isoflavone in soybean hypocotyl and cotyledon calluses under UV-B radiation. The results showed that UV-B radiation significantly up-regulated the gene expression of phenylalanine ammonia lyase (PAL), cinnamate-4-hydroxylase (C4H), 4-coumarate-CoA ligase (4CL), chalcone ketone synthase (CHS), chalcone isomerase (CHI), and isoflavone synthase (IFS), and enhanced their activity in soybean hypocotyl and cotyledon calluses. As a result, isoflavones content increased by 21.23 and 21.75% in soybean hypocotyl and cotyledon calluses, respectively. Among the isoflavones produced, malonyldaidzin was the dominant one in hypocotyl callus, while malonylglycitin and daidzein were the main isoflavones in cotyledon calluses. This study revealed that UV-B radiation induced isoflavone accumulation in soybean calluses, which could be an efficient strategy to improve the nutritional value of food and produce high levels of bioactive secondary metabolites.

Lignification in Zinnia (Zinnia elegans Jacq.) Stem Sections of Different Age: Biochemical and Molecular Genetic Traits

Lignification of the stem in zinnia provides its mechanical properties due to xylem formation, which depends on the stage of plant development and is responsible for the transport of water and minerals. The study was aimed at the lignin deposition, anatomical traits, biochemical markers of lignification, as well as the genetic regulation of this process in zinnia stem cross sections of different age during their radial growth. The anatomical traits were assessed on cross sections. The content of lignin (Cysteine-assisted sulfuric method (CASA) and the thioglycolic acid (TGA) methods), the spectrum of phenolics (by thin layer chromatography (TLC)), the total activity and the variety of class III peroxidases were determined. The expression level of genes regulating phenylpropanoids and lignin biosynthesis were assessed. We suggest that time-specific and organ-specific lignification is determined by the metabolism of phenolic compounds and depends on the expression of genes of the phenylpropanoid pathway. It was shown that in the hypocotyl, during xylem ring formation, lignification was associated with increased expression of phenylalanine ammonia-lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD) genes responsible for the early stages of the phenylpropanoid pathway, and with the rise of class III peroxidases activity, including cationic isoforms. This caused increased content and diversity of phenolics in mature hypocotyl. In epicotyl, which is younger than the hypocotyl, the proportion of ferulic acid among phenolics increased, which could be considered as a marker of lignification in it. The high expression level of CAD and the activity of peroxidases, including anionic isoforms, led to accumulation of lignin. Thus, the hypocotyl and epicotyl, being characterized by different ages, differed in spectrum of phenolics, isoforms of class III peroxidases, expression of the PAL, cinnamate 4-hydroxylase (C4H), peroxidases III class (PRX), and laccase (LAC) genes, and lignin content.

A Cinnamate 4-HYDROXYLASE1 from Safflower Promotes Flavonoids Accumulation and Stimulates Antioxidant Defense System in Arabidopsis.

C4H (cinnamate 4-hydroxylase) is a pivotal gene in the phenylpropanoid pathway, which is involved in the regulation of flavonoids and lignin biosynthesis of plants. However, the molecular mechanism of C4H-induced antioxidant activity in safflower still remains to be elucidated. In this study, a CtC4H1 gene was identified from safflower with combined analysis of transcriptome and functional characterization, regulating flavonoid biosynthesis and antioxidant defense system under drought stress in Arabidopsis. The expression level of CtC4H1 was shown to be differentially regulated in response to abiotic stresses; however, a significant increase was observed under drought exposure. The interaction between CtC4H1 and CtPAL1 was detected using a yeast two-hybrid assay and then verified using a bimolecular fluorescence complementation (BiFC) analysis. Phenotypic and statistical analysis of CtC4H1 overexpressed Arabidopsis demonstrated slightly wider leaves, long and early stem development as well as an increased level of total metabolite and anthocyanin contents. These findings imply that CtC4H1 may regulate plant development and defense systems in transgenic plants via specialized metabolism. Furthermore, transgenic Arabidopsis lines overexpressing CtC4H1 exhibited increased antioxidant activity as confirmed using a visible phenotype and different physiological indicators. In addition, the low accumulation of reactive oxygen species (ROS) in transgenic Arabidopsis exposed to drought conditions has confirmed the reduction of oxidative damage by stimulating the antioxidant defensive system, resulting in osmotic balance. Together, these findings have provided crucial insights into the functional role of CtC4H1 in regulating flavonoid biosynthesis and antioxidant defense system in safflower.

In vitro application of proline in potato tubers under newly emerging bacteria Lelliottia amnigena infection

Biotic stress deleteriously affects growth, development, and productivity in plants. Proline (Pro) plays a significant role in enhancing plant resistance to pathogen infection. However, its effects on reducing Lelliottia amnigena-induced oxidative stress in potato tubers remain unknown. The present study aims to evaluate the in vitro Pro treatment in potato tubers exposed to a newly emerging bacterium, L. amnigena. Sterilized healthy potato tubers were inoculated with 0.3 mL of L. amnigena suspension (3.69 × 107 CFU mL−1) 24 h before Pro (5.0 mM) application. The L. amnigena treatment significantly increased the contents of malondialdehyde (MDA) and hydrogen peroxide (H2O2) in the potato tubers by 80.6 and 85.6%, respectively, compared to the control. Application of proline (Pro) decreased MDA and H2O2 contents by 53.6 and 55.9%, respectively, compared to the control. Application of Pro to L. amnigena-stressed potato tubers increased the activities of NADPH oxidase (NOX), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), 4-coumaryl-CoA ligase (4CL) and cinnamate-4-hydroxylase (C4H) C4H by 94.2, 96.3, 97.3, 97.1, 96.6, 79.3, 96.4, 93.6, and 96.2%, respectively, compared to the control. In comparison to the control, the genes PAL, SOD, CAT, POD, and NOX were significantly increased in the Pro-treated tubers at 5.0 mM concentration. Tubers treated with Pro + L. amnigena increased the transcript levels of PAL, SOD, CAT, POD, and NOX by 2.3, 2.2, 2.3, 2.5, and 2.8-fold respectively, compared to the control. Our findings suggested that pretreatment of tubers with Pro might reduce lipid peroxidation and oxidative stress by enhancing enzymatic antioxidant activity and gene expression.

System network analysis of Rosmarinus officinalis transcriptome and metabolome-Key genes in biosynthesis of secondary metabolites.

Medicinal plants contain valuable compounds that have attracted worldwide interest for their use in the production of natural drugs. The presence of compounds such as rosmarinic acid, carnosic acid, and carnosol in Rosmarinus officinalis has made it a plant with unique therapeutic effects. The identification and regulation of the biosynthetic pathways and genes will enable the large-scale production of these compounds. Hence, we studied the correlation between the genes involved in biosynthesis of the secondary metabolites in R. officinalis using proteomics and metabolomics data by WGCNA. We identified three modules as having the highest potential for the metabolite engineering. Moreover, the hub genes highly connected to particular modules, TFs, PKs, and transporters were identified. The TFs of MYB, C3H, HB, and C2H2 were the most likely candidates associated with the target metabolic pathways. The results indicated that the hub genes including Copalyl diphosphate synthase (CDS), Phenylalanine ammonia lyase (PAL), Cineole synthase (CIN), Rosmarinic acid synthase (RAS), Tyrosine aminotransferase (TAT), Cinnamate 4-hydroxylase (C4H), and MYB58 are responsible for biosynthesis of important secondary metabolites. Thus, we confirmed these results using qRT-PCR after treating R. officinalis seedlings with methyl jasmonate. These candidate genes may be employed for genetic and metabolic engineering research to increase R. officinalis metabolite production.

Cut-Wounding Promotes Phenolic Accumulation in Cucumis melo L. Fruit (cv. Yugu) by Regulating Sucrose Metabolism

The effect of cutting on the molecular changes underlying sucrose metabolism and the phenylpropanoid pathway in melon fruit (cv. Yugu) during storage at 15 °C was investigated. Furthermore, the key metabolites, enzymes, and genes involved in sucrose and phenylpropanoid metabolism were determined. Results showed that the cutting of melon increased the activities of acid invertase (AI), neutral invertase (NI), and sucrose synthase-cleavage (SS-c) and the expressions of CmAI1/2, CmNI1/2, and CmSS1, while sucrose synthase-synthesis (SS-s) and sucrose phosphate synthase (SPS) activities and the CmSS2/3 and CmSPS1/2/4 gene expressions were suppressed. These led to sucrose decomposition and fructose and glucose accumulation in fresh-cut melon at the early stage of storage. Moreover, cutting increased the activity and gene expression of hexokinase, which accelerated the transformation of hexose in fresh-cut melon. In addition, cutting enhanced the activities of phenylalanine ammonia lyase (PAL), cinnamate-4-hydroxylase (C4H), and 4-coumarate-CoA ligase (4CL) and up-regulated the expressions of CmPAL1-9, CmC4H1-4, and Cm4CL1/2/3, which activated phenylpropanoid metabolism and resulted in phenolic accumulation in fresh-cut melon. These findings demonstrate that cutting of melon can enhance sucrose metabolism and phenylpropanoid pathway by regulating the activities and gene expressions of related enzymes. Therefore, cut-wounding promoted the conversion of sugars to supply the necessary substrates for phenolic accumulation in fresh-cut melon.

Diacetyl Inhibits the Browning of Fresh-Cut Stem Lettuce by Regulating the Metabolism of Phenylpropane and Antioxidant Ability.

Enzymatic browning is the main quality issue of fresh-cut stem lettuce (Lactuca sativa L. var. angustana Irish). In this research, the effect of diacetyl on the browning and browning-related mechanisms of fresh-cut stem lettuce was explored. The data showed that diacetyl treatment with 10 μL L-1 inhibited the browning of fresh-cut stem lettuce and extended the shelf life by over 8 d at 4 °C compared with the control. Diacetyl treatment repressed gene expression and decreased the activities of PAL (phenylalanine ammonia-lyase), C4H (cinnamate-4-hydroxylase) and 4CL (4-coumarate-CoA ligase), which thus reduced the accumulation of individual and total phenolic compounds. Moreover, diacetyl enhanced the antioxidant ability and reduced ROS accumulation, improving the anti-browning ability and indirectly suppressing the biosynthesis of phenolic compounds. These results indicated that diacetyl treatment repressed the browning of fresh-cut stem lettuce by regulating the phenylpropanoid metabolism pathway and antioxidant ability. This study is the first to report that diacetyl has an effective anti-browning role for fresh-cut stem lettuce.

Field testing of transgenic aspen from large greenhouse screening identifies unexpected winners.

Trees constitute promising renewable feedstocks for biorefinery using biochemical conversion, but their recalcitrance restricts their attractiveness for the industry. To obtain trees with reduced recalcitrance, large-scale genetic engineering experiments were performed in hybrid aspen blindly targeting genes expressed during wood formation and 32 lines representing seven constructs were selected for characterization in the field. Here we report phenotypes of five-year old trees considering 49 traits related to growth and wood properties. The best performing construct considering growth and glucose yield in saccharification with acid pretreatment had suppressed expression of the gene encoding an uncharacterized 2-oxoglutarate-dependent dioxygenase (2OGD). It showed minor changes in wood chemistry but increased nanoporosity and glucose conversion. Suppressed levels of SUCROSE SYNTHASE, (SuSy), CINNAMATE 4-HYDROXYLASE (C4H) and increased levels of GTPase activating protein for ADP-ribosylation factor ZAC led to significant growth reductions and anatomical abnormalities. However, C4H and SuSy constructs greatly improved glucose yields in saccharification without and with pretreatment, respectively. Traits associated with high glucose yields were different for saccharification with and without pretreatment. While carbohydrates, phenolics and tension wood contents positively impacted the yields without pretreatment and growth, lignin content and S/G ratio were negative factors, the yields with pretreatment positively correlated with S lignin and negatively with carbohydrate contents. The genotypes with high glucose yields had increased nanoporosity and mGlcA/Xyl ratio, and some had shorter polymers extractable with subcritical water compared to wild-type. The pilot-scale industrial-like pretreatment of best-performing 2OGD construct confirmed its superior sugar yields, supporting our strategy.

Protein-protein interactions of the phenylpropanoid pathway in sorghum bicolor.

Phenylalanine ammonia-lyase (PAL) is the first enzyme of the phenylpropanoid pathway followed by cinnamate 4-hydroxylase (C4H), a cytochrome P450 monooxygenase associated with the endoplasmic reticulum of plant cells. PAL and C4H are important for the plant cells due to their involvement in kickstarting the production of primary and secondary metabolites such as phenylpropanoids and lignin. C4H also interacts with cytochrome P450 reductase (CPR; Sorghum bicolor CPR in this study) to hydrolyze trans-cinnamic acid into p-coumaric acid. This study uses fluorescence correlation spectroscopy and single-protein fluorescence tracking of labeled proteins to directly measure the interactions of all three proteins in the absence and presence of their respective substrates. This study also explores specific protein-lipid interactions as a function of state (i.e. oxidation state, heterodimeric state, substrate occupancy, etc.)

Methyl jasmonate facilitates wound healing of Chinese yam tubers via positively regulating the biosynthesis and polymerization of suberin polyphenolics

Suberin is a cell wall-associated heteropolymer composed of suberin polyaliphatics (SPA) and suberin polyphenolics (SPP), which confers a hydrophobic barrier to plants against dehydration and pathogen invasion. Jasmonic acid (JA) plays a positive role in wound-induced SPP deposition in kiwifruit and potato tubers, but the mechanism underlying the regulation of JA on wound healing of Chinese yam tubers remains unknown. In this study, the biochemical and physiological responses to methyl jasmonate (MeJA) and diethyldithiocarbamic acid (DIECA, an inhibitor of JA biosynthesis) treatments in wound yam tubers were investigated. The results showed that exogenous MeJA promoted the production of endogenous JA with increased gene expressions of lipoxygenase (LOX) and 12-oxo-phytodienoic acid reductase (OPR) in wound tubers. The activities and gene expressions of phenylalanine ammonialyase (PAL), cinnamic acid 4-hydroxylase (C4H) and 4-coumarate-CoA ligase (4CL) in wound tubers were pronouncedly enhanced by MeJA, along with increase of SPP monomers, especially, hydroxycinnamic acids (HAs). Meanwhile, MeJA increased the activities and gene expressions of peroxidase (POD), NADPH oxidase (NOX), polyamine oxidase (PAO), and the generation of hydrogen peroxide (H2O2), which were likely to be involved in the polymerization of SPP monomers resulting in SPP deposition. Conversely, inhibition of JA biosynthesis by DIECA reversed the positive impact of MeJA on wound healing process. The results indicate that rapid wound healing in Chinese yam tubers could be induced by MeJA via stimulating phenylpropanoid metabolism, POD activity and H2O2 generation involved in SPP deposition.

β-Cyclodextrin-Based Nitrosoglutathione Improves the Storage Quality of Peach by Regulating the Metabolism of Endogenous Nitric Oxide, Hydrogen Sulfide, and Phenylpropane

Nitrosoglutathione (GSNO) and β-cyclodextrin (β-CD) exhibit positive roles in regulating fruit quality. However, there are few reports about the effects of GSNO and β-CD on enhancing storability and boosting nitric oxide (NO), hydrogen sulfide (H2S), and phenylpropane metabolism in fruits during storage. “Xintaihong” peach were treated with 0.5, 1.0, 1.5 mmol L−1 GSNO in 0.5% (w/v) β-CD solution (GSNO/β-CD). The effects of GSNO/β-CD on endogenous NO, H2S, and phenylpropane metabolism were investigated. Treatment with GSNO/β-CD increased the color difference of peach and inhibited the increase of respiratory intensity, weight loss, and relative conductivity. Treatment with 1.0 mmol L−1 GSNO/β-CD increased the nitric oxide synthase (NOS-like) activity and L-arginine content, thereby promoting the accumulation of endogenous NO. By improving the activities of L-cysteine desulfhydrylase (L-CD), O-acetylserine sulfur lyase (OAS-TL), serine acetyltransferase (SAT), GSNO/β-CD increased the content of endogenous H2S in peach. Treatment with GSNO/β-CD increased the activities of phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4CL), and cinnamic acid-4-hydroxylase (C4H), promoted the increase of total phenols, flavonoids, and lignin in peach. These results indicated that GSNO/β-CD treatment better maintained the quality of peach by improving the metabolism of endogenous NO, H2S, and phenylpropane during storage.

Epsilon-poly-l-lysine increases disease resistance of citrus against postharvest green mold by activating amino acid metabolism and phenolic compounds biosynthesis

AbstractAs a famous fruit worldwide, citrus is susceptible to green mold caused by Penicillium digitatum, which causes large economic losses every year. ε-Poly-l-lysine (ε-PL) is a novel preservative with strong inhibitory effects on fungi, and has the capacity to induce disease resistance in fruit, but the mechanism has been reported rarely, especially in citrus. In the present study, 800 μg/mL ε-PL and P. digitatum spores were inoculated in two different wounds on the citrus pericarp at an interval of 24 h. The results revealed that ε-PL inhibited that the development of green mold without direct contact with P. digitatum, indicating that the disease resistance of citrus was activated. Transcriptome analysis revealed that ε-PL activated amino acid metabolism and phenylpropanoid biosynthesis. Besides, the accumulation of glutamic acid, proline, arginine, serine, lysine, phenylalanine, and tyrosine were changed during storage. In phenylpropanoid biosynthesis, ε-PL increased phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), and 4-coumarate:coenzyme A ligase (4CL) activities and total phenolic and flavonoid contents. Importantly, among these phenolic compounds, ε-PL promoted the accumulation of individual phenolic compounds including ferulic acid, chlorogenic acid, p-coumaric acid, caffeic acid, gallic acid, catechins, epicatechin, and narirutin. In conclusion, ε-PL enhanced the resistance of citrus through amino acid metabolism and accumulation of phenolic compounds. These results improved the knowledge of the mechanism of ε-PL–induced disease resistance and provided a fresh theoretical basis for the use of ε-PL in postharvest citrus preservation.

Water Deficit-Induced Changes in Phenolic Acid Content in Maize Leaves Is Associated with Altered Expression of Cinnamate 4-Hydroxylase and p-Coumaric Acid 3-Hydroxylase

The amino acid phenylalanine is a precursor to phenolic acids that constitute the lignin biosynthetic pathway. Although there is evidence of a role of some phenolic acids in plant responses to pathogens and salinity, characterization of the involvement of phenolic acids in plant responses to drought is limited. Drought reduces water content in plant tissue and can lead to decreased cell viability and increased cell death. We thus subjected maize seedlings to water deficit and evaluated relative water content and cell viability together with p-coumaric acid, caffeic acid and ferulic acid contents in the leaves. Furthermore, we measured the enzymatic activity of cinnamate 4-hydroxylase (EC 1.14.13.11) and p-coumarate 3-hydroxylase (EC 1.14.17.2) and associated these with the expression of genes encoding cinnamate 4-hydroxylase and p-coumarate-3 hydroxylase in response to water deficit. Water deficit reduced relative water content and cell viability in maize leaves. This corresponded with decreased p-coumaric acid but increased caffeic and ferulic acid content in the leaves. Changes in the phenolic acid content of the maize leaves were associated with increased enzymatic activities of cinnamate 4-hydroxylase and p-coumarate hydroxylase. The increased enzymatic activity of p-coumarate 3-hydroxylase was associated with increased expression of a gene encoding p-coumarate 3-hydroxylase. We thus conclude that metabolic pathways involving phenolic acids may contribute to the regulation of drought responses in maize, and we propose that further work to elucidate this regulation may contribute to the development of new maize varieties with improved drought tolerance. This can be achieved by marker-assisted selection to select maize lines with high levels of expression of genes encoding cinnamate 4-hydroxylase and/or p-coumarate 3-hydroxylase for use in breeding programs aimed and improving drought tolerance, or by overexpression of these genes via genetic engineering to confer drought tolerance.

Exogenous piperonylic acid and p-coumaric acid differentially influence crown rot caused by Colletotrichum siamense in octoploid strawberries by regulating phenylpropanoid, flavonoid, and lignin metabolism

ABSTRACT Colletotrichum species crown rot causes the accumulation of metabolites involved in phenylpropanoid biosynthesis in octoploid strawberries. Phenylpropanoid biosynthesis is the first step in the flavonoid and lignin biosynthesis pathways and it plays a key role in plant disease resistance. We therefore aimed to determine the influence of exogenous piperonylic acid (PiA) and p-coumaric acid (p-CA) on crown rot in octoploid strawberry. Piperonylic acid restricted mycelial and lesion growth in strawberry crowns, whereas p-CA enhanced crown rot susceptibility by regulating the accumulation of total phenols, flavonoids, and lignin. The total phenol content induced by PiA significantly increased in strawberries infected with Colletotrichum siamense by promoting the activities of phenylalanine ammonia-lyase, but not trans-cinnamate 4-monooxygenase and 4-coumarate-CoA ligase. Lignin contents were relatively stable in strawberries infected with C. siamense, whereas the caffeoyl coenzyme A methyltransferase and cinnamoyl CoA reductase activities associated with lignin biosynthesis were upregulated by PiA. The infection of C. siamense increased flavonoid contents, whereas PiA decreased flavonoid contents. Overall, PiA enhanced C. siamense crown rot resistance via the phenylpropanoid biosynthesis of total phenols and was less associated with the biosynthesis of lignin and flavonoids.

Effects of methyl jasmonate and NaCl treatments on the resveratrol accumulation and defensive responses in germinated peanut (Arachis hypogaea L.)

In this study, the effects of methyl jasmonate (MeJA) and sodium chloride (NaCl) treatments on the resveratrol biosynthesis and physiology of peanuts during germination were investigated. The results showed that MeJA (150 μM) and NaCl (150 mM) treatments significantly promoted resveratrol biosynthesis in germinated peanuts. MeJA and NaCl treatments promoted resveratrol accumulation by regulating the activities of phenylalanine ammonia lyase (PAL), cinnamic acid 4-hydroxylase (C4H) and 4-coumarate coenzyme A ligase (4CL) and their gene expression levels in cotyledons and non-cotyledons. In addition, both MeJA and NaCl treatments inhibited peanut sprout growth, as evidenced by shorter sprout length, increased malondialdehyde content, and accumulation of reactive oxygen species in cotyledons and non-cotyledons. Both treatments' germinated peanuts responded to the environmental stimuli by raising the activities of antioxidant enzymes and controlling the levels of their gene' expression. Meanwhile, MeJA and NaCl treatments promoted Ca2+ aggregation in the root tips. Therefore, it can be deduced that Ca2+ may help improve the plant's resistance to adversity. In conclusion, treatment with MeJA (150 μM) or NaCl (150 mM) during germination is an effective way to enrich the resveratrol content of peanuts. Germinated peanuts enhance adaptation to the external environment by promoting resveratrol biosynthesis and enhancing antioxidant systems.

The involvement of the phenylpropanoid and jasmonate pathways in methyl jasmonate-induced soft rot resistance in kiwifruit (Actinidia chinensis).

Botryosphaeria dothidea is a major postharvest causal agent of soft rot in kiwifruit. Methyl jasmonate (MeJA) is an important plant hormone that participates as a plant defense against pathogens from a signal molecule. However, the impact and regulatory mechanism of MeJA on the attenuation of kiwifruit fungal decay remains unknown. This work investigated the effects of exogenous MeJA on the enzyme activity, metabolite content and gene expression of the phenylpropanoid and jasmonate pathways in kiwifruit. The results revealed that MeJA inhibited the expansion of B. dothidea lesion diameter in kiwifruit (Actinidia chinensis cv. 'Hongyang'), enhanced the activity of enzymes (phenylalanine ammonia lyase, cinnamate 4-hydroxylase, 4-coumarate: coenzyme A ligase, cinnamyl alcohol dehydrogenase, peroxidase and polyphenol oxidase), and upregulated the expression of related genes (AcPAL, AcC4H, Ac4CL, and AcCAD). The accumulation of metabolites (total phenolics, flavonoids, chlorogenic acid, caffeic acid and lignin) with inhibitory effects on pathogens was promoted. Moreover, MeJA enhanced the expression of AcLOX, AcAOS, AcAOC, AcOPR3, AcJAR1, AcCOI1 and AcMYC2 and reduced the expression of AcJAZ. These results suggest that MeJA could display a better performance in enhancing the resistance of disease in kiwifruit by regulating the phenylpropanoid pathway and jasmonate pathway.

Understanding the changes of phenylpropanoid metabolism and lignin accumulation in wounded cassava root during postharvest storage

The postharvest deterioration of cassava (Manihot esculenta Crantz) root which was caused by the wounds has severely hampered the development of the cassava industry. In this study, the deterioration rate and weight loss, the transcription and enzyme activity of key genes in the phenylpropane metabolism, and the accumulation of lignin and suberin were examined during wound healing of cassava root. The results showed that the deterioration rate and weight loss of cassava-resistant variety SC9 were 4.1 and 1.8 times lower than those of the susceptible SC6 on the seventh day of storage. The activities of phenylalanine ammonia-lyase (PAL), cinnamic acid 4-hydroxylase (C4H), 4-coumarate-CoA ligase (4CL), and cinnamyl alcohol dehydrogenase (CAD) of SC9 were significantly higher on the seventh day than at 0 h. By contrast with SC6, SC9 deposited a large amount of lignin and suberin in the wound site. The structural characteristics of wound healing tissues were analyzed by microscopic observation, revealing that the healing reaction of cassava roots prevented the penetration of toluidine blue and pathogen infection. The expression changes of genes related to the phenylpropanoid metabolism pathway and the accumulation of lignin during wound self-healing provide new ideas for solving postharvest deterioration of cassava roots.