Phenylalanine Ammonia-lyase Gene Research Articles

Tomato SlPUB24 enhances resistance to Xanthomonas euvesicatoria pv. perforans race T3

Solanum lycopersicum var. cerasiforme accession PI 114490 has broad-spectrum resistance to bacterial spot caused by several species of Xanthomonas. Resistance is quantitatively inherited, and a common quantitative trait locus QTL-11B on chromosome 11 has been identified previously. In this study, the SlPub24 gene was characterized in QTL-11B. SlPub24 in PI 114490 was upregulated by infection with X. euvesicatoria pv. perforans race T3, but its transcription was low in the susceptible line OH 88119 whether or not it was infected by the pathogen. The differential expression of SlPub24 between PI 114490 and OH 88119 was due to great sequence variation in the promoter region. The promoter of SlPub24 in OH 88119 had very low activity and did not respond to pathogen infection. Transgenic lines of OH 88119 overexpressing SlPub24 isolated from PI 114490 showed significantly enhanced resistance, while mutants of Slpub24 generated by CRISPR/Cas9 editing showed more susceptibility to race T3 and to other races. The mutants also showed spontaneous cell death in leaves. The expression of the salicylic acid (SA) pathway gene phenylalanine ammonia-lyase (PAL) and signaling-related genes pathogenesis-related (PR1) and nonexpresser of PR1 (NPR1) were influenced by SlPub24. The content of SA in tomato plants was consistent with the level of SlPub24 expression. Furthermore, SlPUB24 interacted with the cell wall protein SlCWP and could regulate the degradation of SlCWP. The expression levels of SlCWP and SlCWINV1, a cell wall invertase gene, showed opposite patterns during pathogen infection. The activity of SlCWINV1 was lower in mutants than in PI 114490. The results are discussed in terms of the roles of the abovementioned genes, and a potential model for SlPUB24-mediated resistance to bacterial spot is proposed.

Reduction of enzymatic browning of fresh-cut Chinese yam (Dioscorea opposita) by UV-C treatment

Herein, we studied the effect of UV-C (shortwave ultraviolet) irradiation on the quality and inhibition of the browning of fresh-cut Chinese yam (Dioscorea opposita). The irradiation of 0, 4, 8, 12, and 24 kJ m-2 were applied to fresh-cut Chinese yam, and quality characteristics were evaluated during 16 days of storage at 4°C. The results indicated that UV-C treatment (8 KJ m-2) effectively decreased the browning degree, polyphenol oxidase (PPO) and peroxidase (POD) activities, and total bacteria count (TBC). However, the phenylalanine ammonia lyase (PAL) activity, PAL gene expression, respiration rate, and total phenol content increased. The UV-C treatment of 8 kJ m-2 resulted in a lower degree of membrane damage, as evidenced by the lower soluble quinone accumulation and browning index (BI), and retained the soluble solid content and hardness during storage. Increasing irradiation intensity would enhance cell damage while did not reduce browning. The results also showed that UV-C treatment alone had great potential to inhibit the browning of fresh-cut vegetables.

Comparative transcriptomic analysis of cantaloupe melon under cold storage with ozone treatment

Ozone treatment was found to delay the postharvest cantaloupe melon decay and improve its intrinsic quality during the cold storage. The transcriptomes of cantaloupe peel and pulp in response to ozone treatment were investigated to reveal the mechanisms using a high-throughput RNA sequencing approach. Results showed that 570 and 313 differentially expressed genes were identified in peel and pulp, respectively. According to these identified genes, the gene ontology and pathway enrichment analysis indicated that the ozone treatment could maintain the firmness of the cantaloupe by changing pectin metabolites and reduction of the ethylene production by regulating relevant genes especially in the peel. The total flavonoid content changes in peel and pulp related to the regulation of phenylalanine ammonia lyase, 4-coumarate-CoA ligase and P450 family genes which further leading to the inhibition of phenylalanine metabolic pathway in peel but promotion of secondary metabolism in pulp. The qRT-PCR results were in accordance with our RNA sequencing results which validated the conclusions. The present study for the first time reveals the mechanism of cantaloupe in response to ozone treatment at a transcriptome level which is of importance for cantaloupe storage.

Phenylalanine ammonia-lyase gene family (PAL): Genome wide characterization and transcriptional expression in jute (Corchorus olitorius)

Jute is one of the important ligno-cellulose bast fiber crops next to cotton. High lignin content in jute fiber makes hindrances during spinning in the textile industry. Phenylalanine ammonia-lyase (PAL), encoded by multigene family, is the first enzyme in the phenylpropanoid pathway which involved in biosynthesis of different secondary metabolites including lignin. A total of 4 PAL genes were identified in jute (Corchorus. olitorius) genome which was being distributed in two chromosomes and clustered into three subfamilies based on phylogenetic analysis. Like PAL genes in other species, CoPALs had similar molecular properties and structure organizations. Expression analysis revealed that CoPAL1 and CoPAl2 were differentially expressed in various jute tissues. Among them, CoPAL1 was predominately expressed in stem tissues suggesting its involvement in lignin accumulation in fiber and can act as a potential target for reducing lignin in jute. Our study provides useful information for future functional characterization of PAL genes in jute.

Physiological Responses of Gamma-Irradiated Onion Bulbs during Storage

The present study aimed to evaluate the effects of different doses of gamma radiation on some physiological characters of onion genotypes and the expression of PAL gene in the best interaction of gamma irradiation dose and onion genotype treatment. To this aim, four onion genotypes (White-Qom, White-Neyshabour, Red-Ridge- Lump, and Red-Ray-Corrugated) irradiated at 0, 30, 60, 90, 120, and 150 Gy. After four months of storage (at 10-15 °C and 70% relative humidity), the effects of gamma rays on the dry matter (DM), protein content, phenylalanine ammonia lyase (PAL) and peroxidase (POD) were investigated. In addition, the expression of PAL gene in the best interaction of gamma irradiation dose and onion genotype treatment was assessed. The result indicated that POD activity was increased by most of the gamma irradiation levels; however, the protein content and PAL activity were decreased. Moreover, dry matter content was found to be highly genotype-dependent. A linear regression (R2= 0.82) between PAL activity and gamma irradiation levels, was observed. PAL activity decreased with increasing in gamma irradiation level, while the expression rate of PAL gene was not significantly changed between irradiated and non-irradiated control, indicating that the radiation might not have direct effects on the gene regulatory elements. These results suggest that gamma irradiation could reduce the PAL activity possibly by controlling abiotic stress sources such as fungal and bacterial stresses.

Antiviral activity of glucosylceramides isolated from Fusarium oxysporum against Tobacco mosaic virus infection.

Natural elicitors derived from pathogenic microorganisms represent an ecologic strategy to achieve resistance in plants against diseases. Glucosylceramides (GlcCer) are classified as neutral glycosphingolipids. GlcCer were isolated and purified from Fusarium oxysporum mycelium. F. oxysporum is a plant pathogenic fungus, abundant in soil and causing severe losses in economically important crops such as corn, tobacco, banana, cotton and passion fruit. In this study we evaluate the capacity of GlcCer in inducing resistance in N. tabacum cv Xanthi plants against Tobacco mosaic virus (TMV). Spraying tobacco plants with GlcCer before virus infection reduced the incidence of necrotic lesions caused by TMV. In addition, plants already infected with the virus showed a reduction in hypersensitive response (HR) lesions after GlcCer treatment, suggesting an antiviral effect of GlcCer. Our investigations showed that GlcCer stimulates the early accumulation of H2O2 and superoxide radicals. In addition, the expression of PR-1 (pathogenesis-related 1, with suggested antifungal action), PR-2 (β-1,3-glucanase), PR-3 (Chitinase), PR-5 (Osmotin), PAL (Phenylalanine ammonia-lyase), LOX (Lipoxygenase) and POX (Peroxidase) genes was highly induced after treatment of tobacco plants with GlcCer and induction levels remained high throughout a period of 6 to 120 hours. Our experiments demonstrate that GlcCer induces resistance in tobacco plants against infection by TMV.

Effect of light quality and tissue origin on phenolic compound accumulation and antioxidant activity in Camellia japonica calli

In Camellia japonica callus culture, the effects of light quality on the accumulation of phenolic compounds were examined. To this end, the calli were cultured under three monochrome [white (W), red (R), and blue (B)] and two mixed [red/blue (RB) and red/green/blue (RGB)] light sources. After 4 weeks of culture, fresh and dry callus weights were determined, and phenolic content was analyzed using high-performance liquid chromatography. We also examined the effects of RGB light on calli derived from four origins (leaf: CL; root: CR; petal: CP; and ovary: CO). Total phenolic and flavonoid content and DPPH radical scavenging activity were highest in calli exposed to RB and RGB. Catechin was detected only in calli exposed to mixed light (RB and RGB). Interestingly, red pigmentation development in CL and CR calli after 2 weeks of culture and organogenic calli in CR and CP samples was observed. Furthermore, expression of the phenylalanine ammonia lyase and chalcone synthase genes was found to be higher in the CR line than in other lines, and total phenolic and flavonoid content was also higher in the CR and CP lines. The findings of the present study revealed that the accumulation of phenolics and flavonoids in callus tissue varies depending on light quality, which stimulates cell division, and may thus affect the proliferation and organogenesis of C. japonica callus. We also established that the effects of light on red pigment expression and the accumulation of bioactive compounds are dependent on the tissue origin of callus material.

Characterisation, expression and functional analysis of PAL gene family in Cephalotaxus hainanensis

Phenylalanine ammonia lyase (PAL) is the first committed step in the formation of phenylpropanoids, and catalyses the deamination of L-phenylalanine (L-Phe) to yield cinnamic acid. While PALs are common in plants, PAL genes involved in alkaloid biosynthesis in Cephalotaxus hainanensis have never been described. To obtain better knowledge of PAL genes and their number and function involved in Cephalotaxus alkaloid biosynthesis four PAL genes were screened and cloned. In vitro enzymatic analysis showed that all four PAL recombinant proteins could convert L-Phe to product trans-cinnamic acid, and showed strict substrate specificity. Moreover, the expression profiles of four ChPALs were analysed using qRT-PCR, which showed that they had higher transcript levels in roots and stems, and that different ChPALs displayed different response sensitivities and change patterns in response to stimuli. Several metabolic compounds were measured in stimulated leaves using UPLC-MS, and indicating the concentration of Cephalotaxus alkaloids and cinnamic acid in leaves subjected to different conditions. These concentrations increased significantly after treatment with 100 mM NaCl, 100 mM mannitol, 100 μM SA and 10 μM ABA. The expression levels of four PAL genes showed indications of upregulation after treatment. These results supply an important foundation for further research on candidate genes involved in the biosynthesis of Cephalotaxus alkaloids.

Phenylalanine ammonia-lyase and phenolic compounds are related to hybrid lethality in the cross Nicotiana suaveolens×N. tabacum.

Hybrid lethality observed in hybrid seedlings between Nicotiana suaveolens and N. tabacum is characterized by browning, initially of the hypocotyls and eventually of entire seedlings. We investigated the mechanism underlying this browning of tissues. A phenylalanine ammonia-lyase (PAL) gene codes an enzyme involved in a pathway producing phenolic compounds related to the browning of plant tissues. The expression of PAL rapidly increased with the induction of hybrid lethality. Phenolic compounds were observed to be accumulated in whole parts of hybrid seedlings. Treatment of hybrid seedlings with L-2-aminooxy-3-phenylpropionic acid (AOPP), an inhibitor for PAL, suppressed browning and decreased the phenolic content of hybrid seedlings. Although programmed cell death (PCD) was involved in hybrid lethality, AOPP treatment also suppressed cell death and enhanced the growth of hybrid seedlings. These results indicated that PAL is involved in hybrid lethality, and phenolic compounds could be the cause of hybrid lethality-associated tissue browning.

Nitric oxide and selenium nanoparticles confer changes in growth, metabolism, antioxidant machinery, gene expression, and flowering in chicory (Cichorium intybus L.): potential benefits and risk assessment.

This experiment was conducted to provide a better insight into the plant responses to nitric oxide (NO) and selenium nanoparticle (nSe). Chicory seedlings were sprayed with nSe (0, 4, and 40 mg l-1), and/or NO (0 and 25 μM). NO and/or nSe4 improved shoot and root biomass by an average of 32%. The nSe40 adversely influenced shoot and root biomass (mean = 26%), exhibiting moderate toxicity partly relieved by NO. The nSe and NO treatments transcriptionally stimulated the dehydration response element B1A (DREB1A) gene (mean = 29.6-fold). At the transcriptional level, nSe4 or NO moderately upregulated phenylalanine ammonia-lyase (PAL) and hydroxycinnamoyl-CoA quinate transferase (HCT1) genes (mean = sevenfold). The nSe4 + NO, nSe40, and nSe40 + NO groups drastically induced the expression of PAL and HCT1 genes (mean = 30-fold). With a similar trend, hydroxycinnamoyl-CoA Quinate/shikimate hydroxycinnamoyl transferase (HQT1) gene was also upregulated in response to nSe and/or NO (mean = 25-fold). The activities of nitrate reductase and catalase enzymes were also induced in the nSe- and/or NO-treated seedlings. Likewise, the application of these supplements associated with an increase in ascorbate concentration (mean = 31.5%) reduced glutathione (mean = 35%). NO and/or nSe enhanced the PAL activity (mean = 36.4%) and soluble phenols (mean = 40%). The flowering was also influenced by the supplements in dose and compound dependent manner exhibiting the long-time responses. It appears that the nSe-triggered signaling can associate with a plethora of developmental, physiological, and molecular responses at least in part via the fundamental regulatory roles of transcription factors, like DREB1A as one the most significant genes for conferring tolerance in crops.

Effect of Phytochrome Deficit on Activity of Ascorbate Peroxidase and Phenylalanine Ammonia-Lyase and Expression of Genes APX1, tAPX, sAPX, and PAL in the Leaves of Arabidopsis thaliana Plants Exposed to UV-A and Red Light

Effect of UV-A radiation (10 W/m2, 2 h) and modifying effect of brief exposure to red light (RL) (1.8 W/m2, 20 min) on photochemical activity of photosystem II (PSII) (Fv/Fm), as well as on activity of ascorbate peroxidase (AsP) and phenylalanine ammonia-lyase (PAL), were investigated in the leaves of 26–28-day-old Аrabidopsis thaliana (L.) Heynh. plants of wild type (WT) and mutants: hy3 deficient in phytochrome B (phyB) and hy2 defective in phytochromobilin synthesis. UV-A reduced photochemical activity of PSII and activities of AsP and PAL. Exposure to RL increased PAL activity in only WT plants and in mutant hy3. Elevation of expression of genes APX1, sAPX, tAPX, and PAL encoding enzymes AsP and PAL was detected upon the exposure to RL and UV-A. For instance, expression of gene APX1 in WT plants and in mutant hy3 rose upon exposure to RL and UV-A; in mutant hy2, it increased only upon UV-A treatment. Expression of gene tAPX in WT plants rose only under the effect of RL, whereas expression of gene sAPX did not rise in any type of treatment. In mutant hy2, expression of the above-named genes decreased upon the effect of RL. Upon joint action of RL and UV-A (RL followed by UV), the negative effect of UV-A on the activity of the total pool of AsP was nullified by RL in only WT plants and in mutant hy3. Partial removal of the negative effect of UV-A on activity of PSII as a result of pretreatment of plants with RL is probably related to a rise in the activity of antioxidant enzymes. This is evident in WT plants whose PSII is more sensitive to RL radiation than in mutants deficient in phytochromes. We believe that PSII resistance to UV-A radiation depends on the potential of the plant antioxidant system, which rises when the share of the active form of phytochrome in its total pool increases as a result of plants’ pretreatment with RL and is partially realized by way of induction of transcriptional activity of antioxidant genes.

Ethylene-mediated apoplastic barriers development involved in cadmium accumulation in root of hyperaccumulator Sedum alfredii

Ethylene is an important phytohormone for plant adaptation to heavy metal stress. However, the effects of ethylene on radial apoplastic transport of Cd remain elusive. This study investigated the role of ethylene on apoplastic barriers development and consequences for Cd uptake in Sedum alfredii. In response to Cd, endogenous ethylene production in hyperaccumulating ecotype (HE) roots was decreased due to the down-regulated expressions of ethylene biosynthesis genes, while the opposite result was observed in non-hyperaccumulating ecotype (NHE). Interestingly, the ethylene emission in HE was always higher than that in NHE, regardless of Cd concentrations. Results of exogenous application of ethylene biosynthesis precursor/inhibitor indicate that ethylene with high level would delay the formation of apoplastic barriers in HE through restraining phenylalanine ammonia lyase activity and gene expressions related to lignin/suberin biosynthesis. Simultaneously, correlation analyses suggest that Cd-induced apoplastic barriers formation may be also regulated by ethylene signaling. By using an apoplastic bypass tracer and scanning ion-selected electrode, we observed that the delayed deposition of apoplastic barriers significantly promoted Cd influx in roots. Taken together, high endogenous ethylene in HE postponed the formation of apoplastic barriers and thus promoted the Cd accumulation in the apoplast of roots.

Transcriptomic Analysis of Root Restriction Effects on Phenolic Metabolites during Grape Berry Development and Ripening

In the present study, the effects of root restriction (RR) on the main phenolic metabolites and the related gene expression at different developmental stages were studied at the transcriptomic and metabolomic levels in "Summer Black" grape berries (Vitis vinifera × Vitis labrusca). The results were as follows: seven phenolic acid compounds, three stilbene compounds, nine flavonol compounds, 10 anthocyanin compounds, and 24 proanthocyanidin compounds were identified by ultra-performance liquid chromatography-high-resolution mass spectrometry. RR treatment significantly promoted the biosynthesis of phenolic acid, trans-resveratrol, flavonol, and anthocyanin and also affected the proanthocyanidin content, which was elevated in the early developmental stages and then reduced in the late developmental stages. The functional genes for phenylalanine ammonia-lyase, trans-cinnamate 4-monooxygenase, 4-coumarate-CoA ligase, shikimate O-hydroxycinnamoyl transferase, chalcone synthase, chalcone isomerase, stilbene synthase, flavonoid 3',5'-hydroxylase, anthocyanidin 3-O-glucosyltransferase, and the transcription factors MYBA1, MYBA2, MYBA3, and MYBA22 were inferred to play critical roles in the changes regulated by RR treatment.

Stage-dependent concomitant microbial fortification improves soil nutrient status, plant growth, antioxidative defense system and gene expression in rice

Stage-dependent concomitant fortification of rice (Oryza sativa L.) varieties PB1612 and CO51 with microbial inoculants Trichoderma asperellum and Pseudomonas fluorescens as seed coating, seedling root inoculation and soil application enhanced growth, activated antioxidant enzymes and modulated defence-related genes in plants. Microbial inoculants improved shoot height, tiller numbers, fresh weight and dry biomass. Co-inoculation was more impactful in enhancing plant growth and development as compared to single inoculation. Single and co-inoculation improved organic carbon (OC) and N, P and K content in the soil substantially. Mean values between control and co-inoculation varied significantly for OC in PB1612 (p0.001) and CO51 (p0.019) and phosphorus content in PB1612 (p0.044) and CO51 (p0.021). Microbial inoculation enhanced soil nutrients and increased their bioavailability for the plants. Total polyphenolics, flavonoids and protein content increased in the leaves following microbial inoculation. Enhanced non-enzymatic antioxidant parameters (ABTS, DPPH, Fe-ion reducing power and Fe-ion chelation) was found in microbe inoculated rice reflecting high free radical scavenging activity in polyphenolics-rich leaf extracts. Increased enzyme activity of superoxide dismutase (SOD), glutathione reductase (GR), phenylalanine ammonia-lyase (PAL), peroxidase (PO), glutathione peroxidase (GPX), ascorbate peroxidase (APX) and catalase (CAT) showed improved ROS scavenging in rice plants having co-inoculation. Over-expression of PAL, cCuZn-SOD and CAT genes in microbial inoculated rice plants was recorded. The study concludes that plant stage-wise concomitant fortification by microbial inoculants could play multi-pronged manifestations at physiological, biochemical and molecular level in rice to positively influence growth, development and defense attributes in plants.

Metabolite profiling of rhizosphere soil of different allelopathic potential rice accessions

BackgroundIdentification of the allelopathy-interrelated metabolites from the allelopathic rice rhizosphere is crucial to understand the allelopathic mechanism of rice, which in turn can promote its applications to farming. In this study, the metabolites from the rhizosphere soil of five different rice lines, including allelopathic rice accession PI312777 (PI) and non-allelopathic rice accession Lemont (Le) as well as their genetic derivatives (e.g., phenylalanine ammonia-lyase (PAL) gene overexpression transgenic lines of PI and Le, namely, PO and LO respectively, and PAL RNA interference line of PI, namely, PR) were identified and comparatively analyzed to explore the positive compounds that are involved in the process of rice allelopathy.ResultsThe results showed that 21 non-polar compounds and 21 polar compounds differed in content in the rhizosphere soil of PI and Le, which include several volatile fatty acids and long-chain fatty acids. The relative contents of fatty acids also differed between PAL overexpressing or RNA interference (RNAi)-silenced line and their wild-type respectively. Acetic acid content also differed among groups, i.e., it is higher in the high allelopathic potential rice. Further analysis showed that different metabolites from the ADS8 resin-extracted phase were more abundant than that those from the ADS21 resin-extracted phase, suggesting that the allelochemicals in root exudates of allelopathic rice are mainly non-polar substances. KEGG annotation of these differential metabolites revealed that these compounds were related to nutrient metabolism, secondary metabolite synthesis, signaling substance synthesis, and toxin degradation.ConclusionsRice allelochemicals deposited in the ADS8 resin-extracted phase were more abundant than those in the ADS21 resin-extracted phase. Allelochemicals in root exudates of allelopathic rice are mainly non-polar substances, and long-chain fatty acids are considered as allelopathy interrelated metabolites.

Cloning, characterization and expression of a phenylalanine ammonia-lyase gene (CcPAL) from cumin (Cuminum cyminum L.)

Phenylalanine ammonia-lyase (PAL) that functions a substantial role in defense mechanisms, growth, and development of the plant, is situated at branching point from primary to secondary metabolism. In this study, using highly conserved sequences of plant PALs registered in GenBank, a partial cDNA clone of cumin (Cuminum cyminum) PAL gene (designated as CcPAL) was isolated. The relative transcript levels of CcPAL gene, its enzyme activity, and accumulation of total phenolics were also analyzed in shoots in response to different stresses. The isolated CcPAL had 414 bp in length with a maximum open reading frame (ORF) of 351 bp and encodes a peptide with 116 amino acids. The deduced peptide sequence of CcPAL has classical PAL domains and is a stable protein. Results of multiple sequence alignment indicate that CcPAL had high similarity with other plant PALs available in the GenBank. Analysis of the phylogenetic tree indicated that CcPAL categorized in the angiosperm-type PAL family and dicotyledon subfamily and clustered together with other PAL from Apiaceae species. Transcription analysis indicated that CcPAL expressed in all tested tissues, but more highly in shoots. Moreever, the expression of CcPAL was found to be induced by cadmium, wounding, salicylic acid (SA) and cold treatments. A positive correlation was found between transcript levels of CcPAL and total phenolics accumulation of cumin shoots in response to different stresses. These results suggest that the CcPAL and phenylpropanoid pathway may play a great role in the biosynthesis of the bioactive compounds and counteracting various stresses in C. cyminum.

Agrobacterium rhizogenes-mediated transformation enhances the antioxidant potential of Artemisia tilesii Ledeb.

Plants belonging to the genus Artemisia L. have been used for medicinal purposes since ancient times. These aromatic plants produce and accumulate a wide range of potent secondary metabolites, many of which have shown antioxidant, antiparasitic, antimicrobial, anti-inflammatory, and even anticancer activities. Enhanced biosynthesis of these compounds is a prerequisite for comprehensive studies of their therapeutic properties and cost-efficient use. Transformation of plants with Agrobacterium rhizogenes native root locus (rol) genes is a promising approach to increase the biosynthesis of plant secondary metabolites. The aim of the present study was to evaluate the effects of A. rhizogenes-mediated transformation on the flavonoid contents in hairy roots of medicinal herb A. tilesii Ledeb. Transgenic A. tilesii hairy root lines were analyzed for stable integration of the rolB and rolC transgenes into the plant genome, total flavonoid contents, antioxidant activities of extracts, and the spatiotemporal expression of two flavonoid biosynthetic genes, phenylalanine ammonialyase (PAL) and chalcone synthase (CHS). The flavonoid contents of A. tilesii directly correlated with the antiradical activity and reducing power of their respective lines, with the greatest antioxidant activity found in the plants with the highest level of total flavonoids. Furthermore, all hairy root lines demonstrated altered expression of plant native PAL and CHS genes. Most importantly, A. rhizogenes-mediated transformation enhanced the biosynthesis of natural antioxidants in A. tilesii, producing almost twice the amount of flavonoids than controls. These findings provide an opportunity for the identification of the bioactive molecules in A. tilesii extracts and their potential health benefits.

Ultrahigh-activity immune inducer from Endophytic Fungi induces tobacco resistance to virus by SA pathway and RNA silencing

BackgroundPlant viruses cause severe economic losses in agricultural production. An ultrahigh activity plant immune inducer (i.e., ZhiNengCong, ZNC) was extracted from endophytic fungi, and it could promote plant growth and enhance resistance to bacteria. However, the antiviral function has not been studied. Our study aims to evaluate the antiviral molecular mechanisms of ZNC in tobacco.ResultsHere, we used Potato X virus (PVX), wild-type tobacco and NahG transgenic tobacco as materials to study the resistance of ZNC to virus. ZNC exhibited a high activity in enhancing resistance to viruses and showed optimal use concentration at 100–150 ng/mL. ZNC also induced reactive oxygen species accumulation, increased salicylic acid (SA) content by upregulating the expression of phenylalanine ammonia lyase (PAL) gene and activated SA signaling pathway. We generated transcriptome profiles from ZNC-treated seedlings using RNA sequencing. The first GO term in biological process was positive regulation of post-transcriptional gene silencing, and the subsequent results showed that ZNC promoted RNA silencing. ZNC-sprayed wild-type leaves showed decreased infection areas, whereas ZNC failed to induce a protective effect against PVX in NahG leaves.ConclusionAll results indicate that ZNC is an ultrahigh-activity immune inducer, and it could enhance tobacco resistance to PVX at low concentration by positively regulating the RNA silencing via SA pathway. The antiviral mechanism of ZNC was first revealed in this study, and this study provides a new antiviral bioagent.

ITRAQ-based proteomic analysis provides insights into the biological mechanism of ammonium metabolism in tea plant (Camellia sinensis L.)

Tea plant prefers ammonium as the dominant inorganic nitrogen source. However, the mechanism behind this preference has not been fully understood. To obtain a better understanding of the preferential assimilation of ammonium in tea, iTRAQ-based proteomics was conducted between 0 and 12 h after ammonium treatment of tea leaves. The quality-related components were positively affected after 12 h, with the highest contents of the four main amino acids and with the primary catechins beginning to decrease. Changes of catechins and differentially expressed proteins suggested that contents of catechins in tea could affect the availability of carbon skeletons needed in photosynthesis and energy metabolism. The biosynthesis of flavonoid was related to ammonium through the regulation of phenylalanine ammonia-lyase (PAL) gene expression and the enzyme activity. After the application of ammonium, the expression of PAL protein and its enzyme activity were both inhibited to decrease the release of ammonium during the reaction converting l-phenylalanine to ammonia and trans-cinnamic acid. Furthermore, to accelerate the metabolism of ammonium, the expression of glutamine synthetase and its isogenes was enhanced, as well as glutamine synthetase activity. Hence, during the ammonium assimilation process, tea plants likely increase the activity of glutamine synthetase and inhibit PAL to balance the ammonium content. These results provide insights into the metabolism of ammonium nutrition orchestrated by primary and secondary metabolic pathways via glutamine synthetase and PAL in tea plant.

Structure and upstream region analysis of phenylalanine ammonia-lyase gene in rice (Oryza sativa L. ssp. japonica) and cucumber (Cucumis sativus L. cv. Chinese long)

Phenylalanine ammonia-lyase (PAL) is the first and main regulatory enzyme in the phenylpropanoid pathway which synthesise Salicylic Acid (SA) from chorismate in plants. The SA considered a key signal in plant-biotrophic pathogen interactions. In the present study, seven PAL genes in rice (Oryza sativa L. ssp. japonica) and 10 in cucumber (Cucumis sativus L. cv. Chinese long) were analysed. Based on the results, cis-regulatory elements in response to SA were distributed in the upstream region of genes significantly. CpG islands observed in the upstream region of rice genes, whereas tandem repeats were observed in the upstream region of both plants. Also, structure of genes such as intron length was considered. Results of the structure and upstream region analysis of PAL genes were correlated with the result of in silico analysis of gene expression. This study provides information about the characteristics of PAL genes and their functions, especially in plant-biotrophic pathogen interaction.