Phenylalanine Ammonia-lyase Gene Expression Research Articles

Elicitation of salicylic acid and methyl jasmonate provides molecular and physiological evidence for potato susceptibility to infection by Erwinia carotovora subsp. carotovora

Among the range of severe plant diseases, bacterial soft rot caused by Erwinia carotovora is a significant threat to crops. This study aimed to examine the varying response patterns of distinct potato cultivars to the influence of E. carotovora. Furthermore, it seeks to highlight the potential role of salicylic acid (SA) and methyl jasmonate (MeJA) in stimulating the antioxidant defence system. We collected eight bacterial isolates from diseased and rotted tubers which were morphologically and physiologically identified as E. carotovora subsp. carotovora. We conducted a greenhouse experiment to analyse the antioxidant responses of three different potato cultivars (Diamont, Kara, and Karros) at various time intervals (2, 4, 6, 8, 12, and 24 h) after bacterial infection (hpi). We assessed the extent of disease damage by applying a foliar spray of 0.9 mM salicylic acid (SA) and 70 μM methyl jasmonate (MeJA). Inoculating with Ecc led to an increase in total phenolic levels, as well as the activities and gene expression of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POX) as time progressed. Additionally, the application of SA and MeJA resulted in a further increase relative to the diseased treatments. The Karros cultivar, unlike the Diamont and Kara cultivars, demonstrated the highest expression levels of PAL, PPO and POX through inoculation, reflecting its higher levels of activity and resistance. Furthermore, the genetic response of potato cultivars to infection at 0 hpi varied depending on their susceptibility. The examination of the rate of PAL activity upregulation following SA or MeJA stimulation clarifies the cultivars' susceptibility over time. In conclusion, the study identified E. carotovora subsp. carotovora as the most virulent isolate causing soft rot disease in potato tubers. It further revealed that the Karros cultivar displayed superior resistance with high activities and gene expression of PAL, PPO and POX, while the cv. Diamont exhibited sensitivity. Additionally, foliar exposure to SA and MeJA induced antioxidant responses, enhancing the potato plants' resistance against Ecc pathogenesis and overall plant defence.

The Effect and Potential Mechanism of Fulvic Acid on Flavonoids in Lemon Leaves

Citrus limon (L.) Burm. f. is a horticultural crop known for its abundance of valuable secondary metabolites, including flavonoids, which are found in its fruits and leaves. Our previous research has shown that treating C. limon with fulvic acid (FA) can enhance the levels of vitamin C, total acid, total sugar, total flavonoids, and phenols in its fruits as well as the volatiles and total flavonoids in its leaves. In this current study, we established a method to analyze eight specific flavonoids in lemon leaves and evaluated the impact of irrigation with FA on the content of these flavonoids over a six-month period using HPLC-DAD/MS analysis. Moreover, we investigated the potential mechanisms of FA through ELISA and q-PCR methods. The results indicated that FA increased the contents of four flavonoids, namely, isoorientin, eriocitrin, vitexin, and rutin, and promoted the activity and gene expression of phenylalanineammonialyase (PAL), 4-coumaric acid coenzyme A ligase (4CL), chalcone synthase (CHS), flavonoid 3′-hydroxylase (F3′H), and flavonol synthase (FLS). Furthermore, the relationship between flavonoid content and the activities of biosynthetic enzymes was analyzed using orthogonal partial least squares discriminant analysis (OPLS-DA), which revealed a positive correlation between seven flavonoid levels and the activity of five biosynthetic enzymes under FA treatment.

Genome-wide identification and expression analyses of phenylalanine ammonia-lyase gene family members from tomato (Solanum lycopersicum) reveal their role in root-knot nematode infection.

Phenylalanine ammonia-lyase (PAL) is a key enzyme and rate-limiting enzyme of phenylpropanoid metabolism, which is a very important pathway in plants, and the secondary products it produces play an important role in plant growth and development, disease resistance, and stress resistance responses. However, PALs still lack systematic characterization in tomato. Based on a bioinformatics methods, PAL family genes were identified and characterized from tomato. qRT-PCR was used to study the expression of PAL genes in cultivated tomato after root-knot nematode infection. In this study, 14 and 11 PAL genes were identified in cultivated and wild tomatoes, and phylogenetic analysis classified them into three subfamilies, with different subfamilies of PAL proteins evolving in different directions in monocotyledonous and dicotyledonous plants. The extensive presence of stress, growth, hormone, and light response elements in the promoter sequences of SlPAL (Solanum lycopersicum) and SpenPAL (Solanum pennellii) genes suggests that this family has a critical role in abiotic stress. Collinearity indicates that members of the tomato and Arabidopsis PAL genes family are from the same ancestor, and the SlPAL10 gene is directly homologous to monocotyledonous rice and maize, suggesting that the SlPAL10 gene was present before monocotyledonous differentiation. Two co-expressed gene modules containing PAL genes were screened by WGCNA, and the core genes in the network were mined and functionally annotated by calculating the connectivity of genes within the modules. In addition, the expression of some genes changed significantly after root-knot nematode infection, with up-regulation of 4 genes and down-regulation of 3 genes. This result provides a data reference for the study of PAL family gene functions in tomato, and also provides a potential application for the subsequent selection of PAL genes in tomato for root-knot nematode resistance.

Enhanced Antioxidant and Anticancer Potential of Artemisia carvifolia Buch Transformed with rol A Gene.

Secondary metabolites have been shown to possess a range of biological functions. Flavonoids, due to their ability to scavenge ROS, are famous antioxidants. The plants of Artemisia species are rich sources of flavonoids; however, the amount of these metabolites is less. In the current study, the flavonoid content was detected and then enhanced by genetically modifying the Artemisia carvifolia Buch with Agrobacterium tumefaciens strain GV3101 carrying rol A gene. The transformation of rol A gene was confirmed with PCR and the gene copy number was confirmed by Southern blot analysis. The HPLC analysis revealed the presence of catechin (3.19 ug/mg DW) and geutisic acid (2.22 ug/mg DW) in transformed plants, unlike wild-type plants. In transformed plants, all detected flavonoids (vanillic acid, rutin, catechine, gallic acid, syringic acid, caffeic acid, coumaric acid, geutisic acid, ferulic acid, and cinnamic acid) were increased up to several folds. Real-time qPCR revealed the higher expression levels of the genes for flavonoid biosynthesis enzymes phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS) in plants transformed with rol A genes, as the expression levels were increased up to 9-20-fold and 2-6-fold, respectively. The rol A transgenic lines T3 and T5 carrying two copies of rol A gene, particularly showed higher expression of both PAL and CHS gene, with the highest expression in T3 line. The transgenic lines demonstrated an average increase of 1.4-fold in the total phenolic content and 1-2-fold in the total flavonoid content as compared to wild-type plants. Total antioxidant capacity and total reducing power were increased up to an average of 1-2-fold and 1.5-2-fold respectively, along with increased free radical scavenging ability. Furthermore, the rol A gene transgenics were found to have much greater cytotoxic capacity than the A. carvifolia wild-type plant against the MCF7, HeLA, and HePG2 cancer cell lines. Current findings show that the rol A gene effectively increases the flavonoid content of A. carvifolia Buch, boosting the plant's capacity as an antioxidant and an anticancer. This is the first-ever report, demonstrating the genetic transformation of Artemisia carvifolia Buch with rol A gene.

Effects of Water Stress on Resveratrol Accumulation and Synthesis in ‘Cabernet Sauvignon’ Grape Berries

Resveratrol (3, 4′, 5 trihydroxy stilbene) is a natural phytoalexin produced by plants in response to biotic and abiotic stresses. It is well known for its cardio-protective, anticarcinogenic, and antioxidant properties. This study characterized physiological and molecular changes in resveratrol synthesis exposed to two levels of water stress at distinct grape berry developmental stages. Physiological data were measured to assess the berry quality. We used high-performance liquid chromatography to study enzyme activity and qRT-PCR to assess the expression levels of genes involved in resveratrol synthesis. The berry development was suppressed under water stress, while the content of total polyphenol, especially resveratrol was enhanced. Related enzymes and genes regulate the changes in resveratrol in plants. Water stress improved the enzyme activities of PAL (phenylalanine ammonia-lyase) and STS (stilbene synthase) after veraison. Moreover, the transcription factors VvMYB14, VvMYB15 and resveratrol synthesis-related genes are also changed. Expression of Vv4CL and VvMYB15 were upregulated during the pre-reversion stage, whereas VvPAL and VvSTS increased throughout development. As the co-substrate of VvSTS, VvCHS decreased during the berry development. Our study demonstrates that water stress regulates resveratrol synthesis through enzymatic activities and the gene expression of PAL and STS.

Nitric oxide treatment delays quality deterioration and enzymatic browning of Agaricus bisporus via reactive oxygen metabolism regulation

AbstractNitric oxide (NO) is a highly reactive gaseous small molecule that regulates plant growth. Sodium nitroprusside (SNP) was used as an NO donor to study the effects of NO treatment on browning and antioxidant activity of button mushrooms (Agaricus bisporus). The findings revealed that exogenous NO treatment alleviated the browning, decreased hardness, and increased weight loss of mushrooms stored at 4°C for 15 days, and reduced the accumulation of reactive oxygen species and membrane lipid peroxidation. Moreover, exogenous NO treatment dramatically increased the anabolism of endogenous NO, maintained the content of antioxidant substances including flavonoids and total phenols, and kept catalase and superoxide dismutase activities at a high level. Further studies revealed that exogenous NO treatment inhibited the activities of enzymes that are involved in browning, which including polyphenol oxidase (PPO) and tyrosinase (TYR), and increased phenylalanine ammonia‐lyase (PAL) activity, with SNP treatment at 0.05 mM being the most effective. Furthermore, SNP treatment at 0.05 mM also inhibited PPO and TYR gene expressions while increasing PAL gene expression. Therefore, our findings suggest that exogenous NO has the potential for development in delaying postharvest browning and maintaining the quality of mushrooms.

Stress response of fresh-cut potatoes to laser irradiation before processing can prevent discoloration and maintain overall quality

Browning is accepted as a main factor affecting quality of fresh cut products. Physical treatments maintaining quality of fresh-cut products have been recently considered by consumer safer than chemical treatments. This study investigated whether preprocess diode laser irradiation can improve the physicochemical quality of fresh-cut potatoes. Laser irradiation at a 450-nm wavelength for 30 min prevented the browning of potato slices during short-term storage at 25 °C. Compared with no treatment, preprocess laser irradiation preserved the appearance and whiteness and inhibited browning and delayed weight loss in potato slices when refrigerated at 4 °C for 96 h. The increases in the total phenol concentration and phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD) activities of fresh-cut potatoes were diminished after laser irradiation. Moreover, the laser irradiation also enhanced antioxidant activities in the samples. The expression of PAL, PPO and POD genes was suppressed by the laser treatment. Therefore, the laser irradiation at 450 nm wavelength for 30 min effectively eliminates discolouration and improves quality of sliced potatoes during cold storage.

Transcriptional and biochemical profiling of defense enzymes in Citrus sinensis during salicylic acid and cinnamon mediated suppression of green and blue mold.

Green and blue mold of citrus are threatening diseases that continuously inflict economic post-harvest loss. The suppressive effect of salicylic (SA) and Cinnamomum verum (CV) on green and blue mold of sweet oranges was investigated in this study. Among five tested plant extracts methanolic extract of Cinnamon caused the highest colony growth inhibition of P. digitatum and P. italicum in an in vitro antifungal assay.The methanolic extract of Cinnamon in combination with SA showed the lowest disease incidence and severity of green and blue mold on citrus fruit without affecting the fruit quality. Transcriptional profiling of defense enzymes revealed that the polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL), and peroxidase (POD) genes were upregulated in fruit treated with CV, SA, and their combination compared to the control. The treatment SA+CV caused the highest upsurge in PPO, POD, and PAL gene expression than the control. Furthermore, the biochemical quantification of PPO, POD and PAL also revealed a similar pattern of activity. The present findings unravel the fact that the escalation in the activity of tested defense enzymes is possibly associated with the reduced incidence of blue and green molds. In conclusion, the study unveils the promising suppressive potential of SA+CV against green and blue mold by regulating the expression of PPO, POD, and PAL genes. Therefore, these treatments can find a role as safer alternatives to chemicals in the management of post-harvest green and blue mold.

Controlling effect and mechanism of burdock fructooligosaccharide against Alternaria fruit rot in blueberry during postharvest

Burdock fructooligosaccharide (BFO), a naturally occurring elicitor derived from the roots of Arctium lappa, can promote postharvest disease resistance in grapes, apples, bananas, and so forth. However, its controlling effect and mechanism against postharvest diseases caused by Alternaria tenuissima in blueberries are unclear. This study showed that BFO treatment restrained the postharvest development of Alternaria fruit rot in blueberries. In the initial stage of fruit storage, BFO treatment induced a hydrogen peroxide burst promoting the blueberry resistance response against A. tenuissima invasion. In addition, BFO treatment increased the activities and gene expression of antioxidant enzymes and pathogenesis-related proteins, such as superoxide dismutase, catalase, peroxidase, ascorbate peroxidase, chitinase, and β-1,3-glucanase, thereby enhancing the fruit resistance to pathogens. The increased activities and gene expression of phenylalanine ammonia-lyase, 4-coumarate CoA ligase, and cinnamate 4-hydroxylase in blueberries were accompanied by increased levels of total phenolics, flavonoids, anthocyanin, and lignin, indicating the activation of the phenylpropanoid pathway. In conclusion, BFO can be a promising elicitor to control the Alternaria fruit rot in blueberries.

Nitric oxide mediates melatonin-induced isoflavone accumulation and growth improvement in germinating soybeans under NaCl stress

The involvement of nitric oxide (NO) in exogenous melatonin (MT)-induced isoflavone accumulation and growth improvement in NaCl-stressed soybeans was investigated in this study. The results demonstrated that MT increased the activity of nitrate reductase (NR) and upregulated the relative expression of NR1, NR2, and nitric oxide synthase1, which subsequently led to an increase in NO content. MT and sodium nitroprusside (SNP, as an NO donor) markedly increased isoflavone content by enhancing the activities of cinnamic acid 4-hydroxylase (C4H) and phenylalanine ammonia lyase (PAL), and by upregulating gene expression of C4H, Isoflavone synthase, PAL, and Chalcone isomerase 1A, which are involved in isoflavone biosynthesis. Moreover, MT, as well as SNP, improved the growth and biomass of NaCl-treated soybeans by increasing the activities of superoxide dismutase, catalase, and peroxidase, and reducing the accumulation of H2O2 and O2•− in soybeans under NaCl stress. These MT-induced responses were entirely reversed by the supply of 4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO, a specific scavenger of NO), which in turn considerably decreased endogenous NO content. These results suggest that NO acts as an important downstream signal molecule, mediating MT-induced isoflavone accumulation and growth improvement in NaCl-stressed soybeans.

PpMYB308 is involved in Pichia guilliermondii-induced disease resistance against Rhizopus rot by activating the phenylpropanoid pathway in peach fruit

Pichia guilliermondii has been shown to control fungal decay in various harvested fruits by inducing disease resistance, but the transcriptional regulatory mechanism remains unclear. In our study, P. guilliermondii treatment induced resistance against soft rot caused by Rhizopus stolonifer in peach fruit, as shown by the reduced disease incidence and severity, increased enzyme activities and gene expression of phenylalanine ammonia-lyase (PAL) and 4-coumarate-CoA ligase (4CL), and promoted the accumulation of total phenolics, total flavonoids and the main individual phenolic compounds (neochlorogenic acid, chlorogenic acid, gallic acid, and rutin). In addition, P. guilliermondii induced the expression of PpMYB308, which was identified as a nucleus‐localized transcriptional activator of PpPAL1 and Pp4CL5 by binding to the MREs (MYB recognition elements). Moreover, the transient overexpression of PpMYB308 in peach fruit enhanced the expression of PpPAL1 and Pp4CL5 and reduced disease incidence and severity. Therefore, the results indicate that PpMYB308 is involved in P. guilliermondii-induced disease resistance against R. stolonifer by activating the phenylpropanoid pathway.

Physiological and Molecular Responses of Vitis vinifera cv. Tempranillo Affected by Esca Disease.

Esca is a multi-fungal disease affecting grapevines. The objective of the study was to evaluate the physiological and molecular response of the grapevine cv. Tempranillo to esca disease, carried out in a vineyard under Mediterranean climatic conditions in western Spain. The photosynthetic pigments in the leaves decreased, with a strong decrease in the photosynthetic efficiency. The proline content increased significantly in the early stages of affected leaves, being possibly involved in the maintenance of lipid peroxidation levels in leaves, which do not increase. The phenol, flavonoid, and phenylpropanoid content decreased in esca-affected leaves, as does the total antioxidant capacity (FRAP), while the polyphenol oxidase (PPO) activity suffers a strong increase with the development of the disease. In affected grapes, the lipid peroxidation and the total phenol content decrease, but not the anthocyanin content. The ascorbate pool decreases with the disease and with time. On the other hand, pool GSH + GSSG is lower in affected leaves, but increases with time. These alterations show a clear change in the redox homeostasis. The expression of genes phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), superoxide dismutase (SOD), and chalcone synthase (ChaS1 and ChaS3) become considerably higher in response to esca, being even higher when the infection time increases. The alteration of AsA and GSH levels, phenolic compounds, PPO activity, proline content, and FRAP, together with the increase of the PAL, PPO, SOD, ChaS1, and ChaS3 gene expression, are clearly implicated in the esca response in plants. The expression of these genes, similar to the PPO activity, can be used as markers of state in the development of the disease.

Enhancing salinity stress tolerance and phenylalanine ammonia lyase gene activity using osmolytes in Moringa seedling production

The salinity of irrigation water is one of the major abiotic stresses that have a variable reaction to soil structure, which has detrimental impacts on seedling development and quality. The osmolytes can help lessen these adverse effects on the establishment of Moringa oleifera seedlings. Therefore, this study was conducted in Egypt (30″53′30, 87″ N and 30″41′29, 77″ E) using polyethylene bags during May – July 2020 and 2021. Three factors in a factorial split –split plot experiment were arranged in randomized complete block design. The main plots were soil structure; sand:clay 2:1 (V/V) and sand 100 %, whereas the subplot treatments were salinity levels; tap water as a control 0.5, 1.5, 4, and 6 dS m−1, and sub–subplot osmolytes; tap water as a control, and glycine betaine, mannitol, proline, and sorbitol all at 0.2 g L−1 as a soil drench. This study aimed to evaluate the effects of osmolytes and soil structure on growth parameters and phenylalanine ammonia lyase (PAL) gene expression in Moringa seedlings. The study concluded that Moringa seedlings in sand:clay performed significantly (P ˂ 0.05) better than those in the sand. With increasing salinity levels, osmolytes enhanced all seedling growth parameters and PAL gene expression compared with the control in the two soil structures. The order of tolerance to salinity stress was sorbitol ˃ proline ˃ mannitol ˃ glycine betaine ˃ control. Moringa seedlings produced in sand:clay treated with 0.2 g L−1 sorbitol and salinity at 4 or 6 dS m−1 were superior in most growth parameters and PAL gene expression.

Identification and Characterization of Arthrobacter nicotinovorans JI39, a Novel Plant Growth-Promoting Rhizobacteria Strain From Panax ginseng.

A bacterial strain JI39 that had plant growth-promoting traits was isolated from the rhizosphere soil of Panax ginseng. It had the ability to produce high indole-3-acetic acid (13.1 μg/ml), phosphate solubilization (164.2 μg/ml), potassium solubilization (16.1 μg/ml), and nitrogen fixation. The strain JI39 was identified to be Arthrobacter nicotinovorans based on morphological, physiological, and biochemical traits and through 16S rDNA sequence analysis. The optimal culture environment for strain growth was 1.0% NaCl, 30°C, pH 6.0, and without UV irradiation. The strain can produce cellulase and protease. The strain JI39 can significantly promote the growth of ginseng. After ginseng seeds were treated with 3 × 108 CFU/ml of JI39 bacterial suspension, the shoot's length was significantly increased by 64.61% after 15 days. Meanwhile, the fresh weight of 2-year-old ginseng roots was significantly increased by 24.70% with a treatment by the 108 CFU/ml bacterial suspension after 150 days in the field. The gene expression of phenylalanine ammonia-lyase (PAL), β-1.3 glucanase (β-1,3-GA), chitinase (CHI), superoxide dismutase (SOD), and peroxidase (POD) of ginseng was upregulated, and it also can improve the soil urease, phosphatase, invertase, and catalase activity. In conclusion, the bacterial strain JI39 could efficiently promote the growth of ginseng and has the potential to be a good microbial fertilizer for ginseng.

Candidate marker genes and enzymes for selection of potato with resistance to early blight, caused by Alternaria alternata

Early blight, caused by Alternaria alternata (Fr.) Keissler is a serious disease of potato and other cultivated Solanum species. The molecular components defining defense responses to A. alternata in potato are limited. Host transcript accumulation after A. alternata inoculation of six potato genotypes (10/33/R1, 3/33/R2 and 21/33/R2, resistant to the pathogen, and 8707/106, 8703/804 and 8707/112, susceptible) was examined to develop understanding of mechanisms of their responses to A. alternata genotypes. The marker genes PR-2, ChtA, PR-5, PR1-b, PIN2, ERF3, PAL and LOX, activity of catalase (CAT), superoxide dismutase (SOD), peroxidase (POX), polyphenol oxidase (PPOs) and phenylalanine ammonia-lyase (PAL), as well as biomass growth parameters, were analysed. Expression of PR-2, ChtA, PR-5, PR1-b and PAL genes was greatly increased in the inoculated resistant genotypes compared to the susceptible genotypes and un-inoculated controls. Transcription levels of PIN2, ERF3 and LOX genes were decreased in resistant inoculated plants. Simultaneously, activities of POX, SOD and PPOs were greatly increased in the inoculated resistant host genotypes, compared to the susceptible and non-inoculated controls. CAT activity in genotype 21/33/R2 and PAL activity in resistant genotypes 21/33/R2 and 10/33/R1 increased in the susceptible and non-inoculated. Host growth parameters of inoculated plants decreased compared to un-inoculated controls. Knowledge of changes in gene expression levels and enzyme production in defense processes in infected potato plants can inform future studies to identify the defense mechanisms, and assist generation of potato cultivars resistant to early blight.

Genome-wide identification and analysis of the PAL genes from the orchids Apostasia shenzhenica, Dendrobium catenatum and Phalaenopsis equestris

Phenylalanine ammonia-lyase (PAL) is a key gateway enzyme that connects the phenylpropanoid pathway to primary metabolism. The phenylpropanoid pathway plays a vital role in the growth and environmental adaptation of many plants leading to the production of valuable bioactive compounds with industrial and medical applications. In the present study, nine putative PAL genes from three orchids were identified; five in Apostasia shenzhenica and two each in Dendrobium catenatum and Phalaenopsis equestris. Eighteen motifs and four major conserved functional domains were identified as reported in PAL proteins of other species. All the nine PALs were stable based on their computed physicochemical properties and localized in the cytoplasm. The three-dimensional structures of PALs revealed a homo-tetrameric structure consisting of four identical subunits. A total of 21 cis-regulatory elements with known functions were identified from the promoter regions of all PALs which are responsible for various plant responses to light, stress and growth regulators like auxins, gibberellins and abscisic acid. Phylogenetic analysis showed that the studied PAL proteins clustered in two major clades (clade I and II), placing dicot and monocot PALs in two separate monophyletic clades. In silico gene expression of the identified PALs in different vegetative and reproductive tissues revealed the differential expressions based on tissue type and disclosed that the expression of PAL genes was upregulated in all the tissues examined with an exception of PePAL leaf samples where no expression was detected, however, the same being highly expressed in reproductive tissues (PePAL1-labellum; PePAL2-sepal). In case of AsPALs, the expression was found to be highest in reproductive tissues (AsPAL4-maximum in inflorescence). On the other hand, the expression of DcPALs was found to be highest in vegetative tissues (DcPAL2-maximum in root). Based on the medicinal importance of orchids and the significant role of PAL genes in synthesis of bioactive compounds, the functional characterization of PAL genes can be further exploited in genetic improvement of medicinal orchids. Communicated by Ramaswamy H. Sarma

Phenylpropanoid metabolism enzyme activities and gene expression in postharvest melons inoculated with Alternaria alternata

This study explored the mechanism of melon resistance to Alternaria alternata (A. alternata) infection in Jiashi and 86-1 melons. Melons were inoculated with A.alternata and the change in lesion diameter was measured. The changes in cinnamic acid-4-hydroxylase (C4H), phenylalanine ammonia lyase (PAL), and 4-coumaric acid coenzyme A ligase (4CL) activity and gene expression were studied in the pericarp tissues of Jiashi and 86-1 melons. The lesion diameter was smaller in Jiashi melon than in 86-1 melon, and the pericarp lesions were smaller than pulp lesions, indicating that Jiashi melon can resist A. alternata infection better than 86-1 melon. After inoculation with A. alternata, the C4H, PAL, and 4CL activities of Jiashi and 86-1 melons peaked in the middle and late storage period, and the peak was higher in Jiashi melons. The gene expression changes were consistent with the enzyme activity. The C4H, PAL, and 4CL gene expression was significantly higher in Jiashi melon pericarp than in 86-1 melon, and the C4H, PAL, and 4CL activities in Jiashi melon were positively correlated with their gene expression, confirming the role of phenylpropanoid metabolism enzymes in resistance to A. alternata.

Transcriptomic Response of Huanglongbing-Infected Citrus sinensis Following Field Application of a Microbial Fermentation Product.

Huanglongbing (HLB) is considered the most destructive disease in Citrus production and threatens the future of the industry. Microbial-derived defense elicitors have gained recognition for their role in plant defense priming. This work assessed a 5% (V/V) microbial fermentation application (MFA) and its role in the elicitation of defense responses in HLB-infected Citrus sinensis trees following a foliar application with a pump sprayer. Using a PCR detection method, HLB infection levels were monitored in healthy and infected trees for 20months. Nutrient analysis assessed N, P, K, Ca, Mg, Mn, Zn, Fe, B, and Cu concentrations in the trees. MFA significantly increased Cu concentrations in treated trees and resulted in the stabilization of disease index (DI) in infected trees. Initial real-time qPCR analysis of defense-associated genes showed a significant increase in pathogenesis-related protein 2 (PR2) and phenylalanine ammonia lyase (PAL) gene expression in healthy and HLB-infected trees in response to MFA. Gene expression of PR2 and PAL peaked 6h post-microbial fermentation application during an 8-h sampling period. A transcriptomic assessment using GeneChip microarray of the hour 6 samples revealed differential expression of 565 genes when MFA was applied to healthy trees and 909 genes when applied infected citrus trees when compared to their respective controls. There were 403 uniquely differentially expressed genes in response to MFA following an intersectional analysis of both healthy and infected citrus trees. The transcriptomic analysis revealed that several genes associated with plant development, growth, and defense were upregulated in response to MFA, including multiple PR genes, lignin formation genes, ROS-related genes, hormone synthases, and hormone regulators. This study provides further evidence that MFA may play an important role as a plant elicitor in an integrated pest management strategy in citrus and other agronomically important crops.

Triacontanol attenuates drought-induced oxidative stress in Brassica juncea L. by regulating lignification genes, calcium metabolism and the antioxidant system

Effect of triacontanol on drought-induced stress was studied in Brassica juncea L. Foliage of sixteen-days-old plants was sprayed with concentrations (0, 10, 20 and 30 μM) of triacontanol (TRIA) for 7 days. Subsequently, plants were subjected to drought stress (10% polyethylene glycol, PEG6000) for 7 days. Drought stress increased oxidative stress (TBARS, O2●- and H2O2), however, their contents were reduced by TRIA. Total soluble sugars, reduced glutathione, and proline content in stressed plants were increased by TRIA. Activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), catalase (CAT), and phenylalanine ammonia-lyase (PAL) activity were significantly increased in a dose-dependent manner with TRIA. Potassium (K+) level declined, while magnesium (Mg2+) and calcium (Ca2+) contents increased. The elevated level of lignin under drought with TRIA was significantly associated with MYB46 and PAL gene expression patterns. Altogether, our results suggest that foliar spray of 20 μM TRIA was more operative in reducing the negative impact of drought stress in B. juncea by regulating the antioxidant system, calcium, and lignification.

Effect of graphene / metal nanocomposites on the key genes involved in rosmarinic acid biosynthesis pathway and its accumulation in Melissa officinalis

BackgroundRecently, numerous investigations have been done to study graphene and silver nanoparticle in the fields of agriculture and medicine. In the present study, the green synthesis of nanoparticles with two concentrations (0, 40, 60 mM) and their effect on the molecular and biochemical biosynthesis pathway of rosmarinic acid in a new method, low cost, and safe for the environment has been investigated. The transcript levels of key genes in the rosmarinic acid biosynthesis pathway (Tyrosine aminotransferase, rosmarinic acid synthase, and phenylalanine-ammonia lyase) were studied using real-time quantitative polymerase chain reaction. Then, the rosmarinic acid content was evaluated using HPLC.ResultsThe results showed that a concentration-dependent manner was observed in treated plants. At the biochemical level, the use of nanocomposites at concentration of 40 mM showed higher soluble carbohydrate (37%), flavonoids (21%), total phenol (35%) as well as total protein (47%) compared to the control plants. HPLC results showed that rosmarinic acid content in the treated plants with a low concentration of nanocomposite (40 mM) was more affected than plants treated with a high concentration of nanocomposite (60 mM) (26%) and also compared to other treatments. At the molecular level, the result showed that Tyrosine aminotransferase and rosmarinic acid synthase gene expression was positively correlated with both silver nanoparticle concentrations and nanocomposite treatments, but phenylalanine-ammonia lyase gene expression was positively correlated only with nanocomposite at 40 mM concentration.ConcludeIt can conclude that the nanocomposite at low concentration is more likely to induce molecular and biochemical parameters. And also, in the rosmarinic acid biosynthesis pathway, the Tyrosine aminotransferase -derived pathway is more efficient than the phenylalanine-ammonia lyase -derived pathway by causing a nano-elicitor. Therefore, it was concluded that studied elicitor at low concentration, can create plants with higher production capacity.