PAL Activity Research Articles

Study on the Regulation Mechanism of 1-MCP Combined with SO2 Treatment on Postharvest Senescence of Bamboo Shoots (Chimonobambusa quadrangularis) in Karst Mountain Area

Fresh bamboo shoots (Chimonobambusa quadrangularis) are subjected to senescence (e.g., lignification and browning) during postharvest storage. This study investigated the effects of 1-MCP and SO2 treatment on bamboo shoot senescence and its regulation mechanism in order to extend bamboo shoot storage time. 1-MCP and SO2 treatments significantly inhibited the browning and lignification of fresh bamboo shoots during storage, according to the results. Its lower browning index and lignin content are directly related to its lower lignin content compared to the CK control group. The browning index and lignin content of the 1-MCP + SO2 treatment during the late storage period were 90.55% and 81.50% of the CK treatment, respectively. The result of the in-depth analysis suggested that 1-MCP and SO2 treatments reduced nutrient loss and maintained the nutritional value of bamboo shoots by inhibiting respiration and physiological metabolism. The PPO activity was inhibited to inhibit the browning process. Moreover, the scavenging ability of ROS was enhanced, the accumulation of MDA was inhibited, and the senescence of bamboo shoots was delayed after higher contents of total flavonoids and ascorbic acid were maintained and the activities of ascorbic acid peroxidase and superoxide dismutase were stimulated. Furthermore, lignin biosynthesis was hindered, and the lignification of bamboo shoots was delayed after the activities of POD and PAL were inhibited. In brief, 1-MCP + SO2 treatment is capable of inhibiting the physiological metabolism, browning, and lignification of bamboo shoots, maintaining good quality during storage, and delaying the senescence of bamboo shoots. Clarifying the senescence mechanism of bamboo shoots is of great significance for expanding the bamboo shoot industry and slowing down rocky desertification in karst mountainous areas.

Induction of wheat resistance by Streptomyces sp. HU2014 strain

Goal. To determine changes in the activity of enzymes (POD, PAL and GLU) of Triticum aestivum when Streptomyces sp. HU2014, Rhizoctonia cerealis G11 are introduced into the soil and their simultaneous application.
 Methods. Laboratory: cultivation of microorganisms and wheat plants, introduction of actinomycetes and fungus into the soil. Physico-chemical: POD, PAL and GLU colorimetry. Analytical and mathematical: analysis of the obtained results and their statistical comparison.
 Results. Changes in the activity of enzymes (POD, PAL and GLU) were noted in the leaves of wheat plants at different time intervals, compared to the control variant. The change manifested mostly in the increase of their activity. The maximum amount of enzyme activity was noted on one variety ZM22: on the third day of POD when inoculated according to the CKP scheme (15762.69 U/g) and GLU when introducing the microorganism into the soil according to the PF3 scheme (28.45 U/g); on the fourth day of the PAL study according to the treatment scheme PF3 (29.37 U/g). The induction of resistance was also determined by the wheat variety.
 Conclusions. The activity of POD, PAL and GLU was determined by the plant treatment scheme, time period and genotype of the crop. In most cases, during soil treatment with microorganisms, the activity of all three studied enzymes from the leaves of three varieties of wheat increased in different periods of time, compared to the control. The activity of PAL enzyme increased to the greatest extent. It was established that the activity of the POD enzyme was mostly determined by R. cerealis and the dual use of microorganisms, the PAL enzyme by a strain of Streptomyces sp. HU2014, and the GLU enzyme — by inoculation with a phytopathogen and introduction of actinomycetes. That is, changes in the activity of all three enzymes were mostly determined by the strain of Streptomyces sp. HU2014. At the same time, it was shown that R. cerealis G11 mainly induced the defense system of AK58 and ZM22 varieties, and HU2014 induced the defense of BN307.

Analysis of the Formation of Characteristic Aroma Compounds by Amino Acid Metabolic Pathways during Fermentation with Saccharomyces cerevisiae.

Amino acid metabolic pathways can have profound impacts on the activities of key enzymes in the biosynthesis of specific aroma compounds during yeast fermentation. Aroma compounds, pyruvic acid and glucose were monitored in relation to the key enzymes of leucine aminotransferase (LTR), phenylalanine aminotransferase (PAL), pyruvate kinase (PK) and acetyl-CoA in the amino acid metabolic pathways during the fermentation of simulated juice systems with added amino acids in order to explore the formation of characteristic aroma compounds. The addition of L-phenylalanine or L-leucine to the simulated juice systems significantly improved the activities of PK, PAL and LTR, and the content of acetyl-CoA, and significantly increased the concentrations of phenylethyl alcohol, octanoic acid, isoamyl acetate, phenylethyl acetate, ethyl hexanoate and ethyl caprylate during fermentation. Correlation analysis showed that there was a significant positive correlation between PAL, LTR, PK and acetyl-CoA and pyruvic acid formation. Path analysis revealed that the addition of amino acids affected the metabolism of pyruvate to alcohols, acids and esters to some extent.

Physiological response of CmWRKY15-1 to chrysanthemum white rust based on TRV-VIGS.

Chrysanthemum White Rust (CWR) caused by Puccinia horiana Henn. is a major disease in the production process of chrysanthemum, which is widely spread all over the world and can be called "cancer" of chrysanthemum. To clarify the disease resistance function of disease resistance genes can provide a theoretical basis for the utilization and genetic improvement of chrysanthemum resistant varieties. In this study, the resistant cultivar 'China Red' was used as the experimental material. We constructed the silencing vector pTRV2-CmWRKY15-1 and obtained the silenced line named TRV-CmWRKY15-1. The results of enzyme activity after inoculation with pathogenic fungi showed that the activities of antioxidant enzymes SOD, POD, CAT and defense-related enzymes PAL and CHI in leaves were stimulated under the stress of P. horiana. In the WT, the activities of SOD, POD and CAT at the peak value were 1.99 times, 2.84 times and 1.39 times higher than that in TRV-CmWRKY15-1, respectively. And the activities of PALand CHI at the peak were 1.63 times and 1.12 times of TRV-CmWRKY15-1. The content of MDA and soluble sugar also confirmed that chrysanthemum was more susceptible to pathogenic fungi when CmWRKY15-1 was silenced. The expression levels of POD, SOD, PAL and CHI at different time points showed that the expressions of defense enzyme related genes were inhibited in TRV-WRKY15-1 under the infection of P. horiana, which weakened the ability of chrysanthemum to resist white rust. In conclusion, CmWRKY15-1 may increased the resistance of chrysanthemum to white rust by increasing the activity of protective enzyme system, which laid a foundation for breeding new varieties with disease resistance.

Salinity Alleviation and Reduction in Oxidative Stress by Endophytic and Rhizospheric Microbes in Two Rice Cultivars.

Increased soil salinity poses serious limitations in crop yield and quality; thus, an attempt was made to explore microbial agents to mitigate the ill effects of salinity in rice. The hypothesis was mapping of microbial induction of stress tolerance in rice. Since the rhizosphere and endosphere are two different functional niches directly affected by salinity, it could be very crucial to evaluate them for salinity alleviation. In this experiment, endophytic and rhizospheric microbes were tested for differences in salinity stress alleviation traits in two rice cultivars, CO51 and PB1. Two endophytic bacteria, Bacillus haynesii 2P2 and Bacillus safensis BTL5, were tested with two rhizospheric bacteria, Brevibacterium frigoritolerans W19 and Pseudomonas fluorescens 1001, under elevated salinity (200 mM NaCl) along with Trichoderma viride as an inoculated check. The pot study indicated towards the presence of variable salinity mitigation mechanisms among these strains. Improvement in the photosynthetic machinery was also recorded. These inoculants were evaluated for the induction of antioxidant enzymes viz. CAT, SOD, PO, PPO, APX, and PAL activity along with the effect on proline levels. Modulation of the expression of salt stress responsive genes OsPIP1, MnSOD1, cAPXa, CATa, SERF, and DHN was assessed. Root architecture parameters viz. cumulative length of total root, projection area, average diameter, surface area, root volume, fractal dimension, number of tips, and forks were studied. Confocal scanning laser microscopy indicated accumulation of Na+ in leaves using cell impermeant Sodium Green™, Tetra (Tetramethylammonium) Salt. It was found that each of these parameters were induced differentially by endophytic bacteria, rhizospheric bacteria, and fungus, indicating different paths to complement one ultimate plant function. The biomass accumulation and number of effective tillers were highest in T4 (Bacillus haynesii 2P2) plants in both cultivars and showed the possibility of cultivar specific consortium. These strains and their mechanisms could form the basis for further evaluating microbial strains for climate-resilient agriculture.

Contribution of Sucrose Metabolism in Phloem to Kiwifruit Bacterial Canker Resistance.

Kiwifruit bacterial canker, caused by Pseudomonas syringae pv. actinidiae (Psa), is a catastrophic disease affecting kiwifruit worldwide. As no effective cure has been developed, planting Psa-resistant cultivars is the best way to avoid bacterial canker in kiwifruit cultivation. However, the differences in the mechanism of resistance between cultivars is poorly understood. In the present study, five local kiwifruit cultivars were used for Psa resistance evaluation and classified into different resistance categories, tolerant (T), susceptible (S), and highly susceptible (HS), based on their various symptoms of lesions on the cane. Susceptible and highly susceptible varieties had a higher sucrose concentration, and a greater decrease in sucrose content was observed after Psa inoculation in phloem than in tolerant varieties. Three invertase activities and their corresponding gene expressions were detected in the phloem with lesions and showed the same trends as the variations in sucrose concentration. Meanwhile, after Psa inoculation, enzyme activities involved in antioxidant defense responses, such as PAL, POD, and CAT, were also altered in the phloem of the lesion position. With no differences among cultivars, PAL and POD activities in phloem first increased and then decreased after Psa inoculation. However, great differences in CAT activities were observed between T and S/HS categories. Our results demonstrate that sucrose content was negatively correlated with the disease resistance of different cultivars and that the increase in immune response enzymes is likely caused by increased sucrose metabolism in the phloem.

Sargassum vulgare extract as a bio‐elicitor of natural stilbenes production and antioxidant potential in peanut (Arachis hypogaea L.) sprouts

SummaryTrans‐resveratrol is a natural polyphenolic compound, belonging to the class of stilbenes. It is known for its various pharmacological properties but limited bioavailability. Our objective was to evaluate for the first time the effect of an extract of Sargassum vulgare on resveratrol, piceatannol and piceid production in peanut (Arachis hypogaea) sprouts. Treatments with rising concentrations of seaweed extract were assessed in ‘Trabelsia’, ‘Chanfakhi’ and ‘American’ peanut varieties after 7 days of incubation. Liquid chromatography‐mass spectrometry was performed to quantify targeted compounds. Total phenols and flavonoids content, PAL and TAL activity and DPPH radical scavenging activity were also determined. A significant genotype effect was demonstrated, as quite exceptionally, in ‘Trabelsia’ the resveratrol content was increased by a factor 110 by elicitation with 8% extract. Piceatannol, piceid, TPC, TFC, PAL, TAL, and DPPH radical scavenging activity confirmed the same trend. This study provides a new insight into an effective approach to enable the accumulation of resveratrol and its derivatives in peanut sprouts for use as a functional food.

A Joint Transcriptomic and Metabolomic Analysis Reveals the Regulation of Shading on Lignin Biosynthesis in Asparagus.

Asparagus belongs to the Liliaceae family and has important economic and pharmacological value. Lignin plays a crucial role in cell wall structural integrity, stem strength, water transport, mechanical support and plant resistance to pathogens. In this study, various biological methods were used to study the mechanism of shading on the asparagus lignin accumulation pathway. The physiological results showed that shading significantly reduced stem diameter and cell wall lignin content. Microstructure observation showed that shading reduced the number of vascular bundles and xylem area, resulting in decreased lignin content, and thus reducing the lignification of asparagus. Cinnamic acid, caffeic acid, ferulic acid and sinapyl alcohol are crucial intermediate metabolites in the process of lignin synthesis. Metabolomic profiling showed that shading significantly reduced the contents of cinnamic acid, caffeic acid, ferulic acid and sinapyl alcohol. Transcriptome profiling identified 37 differentially expressed genes related to lignin, including PAL, C4H, 4CL, CAD, CCR, POD, CCoAOMT, and F5H related enzyme activity regulation genes. The expression levels of POD, CCoAOMT, and CCR genes were significantly decreased under shading treatment, while the expression levels of CAD and F5H genes exhibited no significant difference with increased shading. The downregulation of POD, CCoAOMT genes and the decrease in CCR gene expression levels inhibited the activities of the corresponding enzymes under shading treatment, resulting in decreased downstream content of caffeic acid, ferulic acid, sinaperol, chlorogenic acid and coniferin. A significant decrease in upstream cinnamic acid content was observed with shading, which also led to decreased downstream metabolites and reduced asparagus lignin content. In this study, transcriptomic and metabolomic analysis revealed the key regulatory genes and metabolites of asparagus lignin under shading treatment. This study provides a reference for further understanding the mechanism of lignin biosynthesis and the interaction of related genes.

Cloning and Disease Resistance Analysis of the Maize ZmBON3 Gene

(1) Corn is the most widely planted food crop, feed crop, and economic crop in the world, and plays an important role in agricultural production and national economy development. The copine gene, also known as the BONZAI gene, encodes a Ca2+-dependent phospholipid membrane binding protein that is widely present in eukaryotes. It has been found that the copine protein is a negative regulator of disease resistance regulation and plays a key role in plants’ disease resistance response. In this study, the Agrobacterium-tumefacien-mediated method was used to successfully obtain T2 generation ZmBON3-gene-overexpressing plants and gene-edited plants. Related phenotypes and molecular identification showed that the disease resistance of overexpression plants was significantly reduced, and the disease resistance of gene-edited plants was significantly increased, which verified that the ZmBON3 gene was a negative regulatory gene. By detecting the physiological indexes related to defense, it was found that the content of H2O2 and the enzyme active water of CAT, POD, SOD, and PAL in ZmBON3-gene-edited plants was higher than those in the control plants and ZmBON3-gene-overexpressing plants, and the content of H2O2 and CAT, POD, and SOD in ZmBON3-gene-overexpressing plants was significantly higher than that in the control plants and ZmBON3-gene-overexpressing plants. The enzyme activity of PAL was the lowest. By detecting the expression of key genes of defense-related signaling pathways, it was found that ZmBON3 may be involved in the related defense processes mediated by the R gene, SA pathway, JA pathway, and ABA pathway. In addition, ZmBON3-geneedited plants showed obvious dwarf phenomenon at the seedling stage, but this did not affect the ear length, axis diameter, ear row number, and grain color.

Positive involvement of HCO<sub>3</sub><sup>–</sup> in modulation of melon resistance to powdery mildew

Inorganic salts such as KHCO₃ are considered as potential powerful weapons for protecting plants from disease challenges, while their effects remain largely unknown on melon (<italic>Cucumis melo</italic> L.) resistance to powdery mildew caused by <italic>Podosphaera xanthii</italic>. In this study, the alleviatory effects of KHCO₃ were physiologically explored on <italic>P. xanthii</italic>-infected seedlings of 'Yangjiaomi', an <italic>agrestis</italic> melon cultivar being susceptible to powdery mildew, by exogenous spraying at 7 d after inoculation (DAI) and 2 d before inoculation (DBI), respectively. The significantly improved resistance to <italic>P. xanthii</italic> was observed in melon seedlings sprayed with 2.5 g·L⁻¹ KHCO₃ (pH 8.54). Further investigation showed that the activities of PAL and PPO, as well as the accumulation of resistance-benefiting secondary metabolites, were stimulated by KHCO₃ treatments. Meanwhile, the activities of SOD, POD and CAT were significantly increased, and the contents of O₂^.−, H₂O₂ and MDA were dramatically lowered in the KHCO₃-sprayed seedlings than those in the H₂O-sprayed seedlings. Another four treatments [H₂O, KOH (pH 8.54), 1.86g·L⁻¹ KCl and 2.5g·L⁻¹ KHCO₃ (pH 8.54)] were carried out for melon seedlings at 2 DBI. The significantly decreased disease index and the stimulated ROS and phenylpropanoid metabolic pathways were only observed for the KHCO₃-sprayed group, suggesting the crucial roles of HCO₃⁻ involved in the protection of melon seedlings from powdery mildew. Collectively, our results provide new physiological insights into inorganic salt-mediated plant protection and could benefit the green production of melon in the future.

Effects of Different Treatments on White-blush of Fresh-cut Carrots During Storage

In order to screen out the preservatives that had better effects on inhibiting the white-blush of freshcut carrots, prolong its shelf life. Using fresh carrots as the test material, the effects of different treatments on the white-blush of fresh-cut carrots during storage were compared, and the changes in whiteness value of fresh-cut carrots in each group were analyzed. Other relevant physical and chemical indicators were measured. The results showed that compared with other treatment groups, the onion treatment group had the lowest whiteness index, the strongest antioxidant capacity, and the best quality of fresh-cut carrots. This indicated that onions were suitable for processing fresh-cut carrots, which cold better inhibit the activities of POD, PAL, and other enzymes, inhibit the white-blush of fresh-cut carrots, and delay their aging.

Identification of Resistance to Pathogenesis Related Protein GmPR1L in Tobacco Botrytis cinerea Infection

Soybean (<i>Glycine max</i> (Linn.) Merr.) annual leguminous crop is cultivated all over the world. The occurrence of diseases has a great impact on the yield and quality of soybean. In this study, based on the RNA-seq of soybean variety M18, a complete CDS (Coding sequence) <i>GmPR1L</i> of the pathogenesis-related protein 1 family was obtained, which has the ability to resist fungal diseases. The overexpression vector and interference expression vector were transferred into tobacco NC89, and the resistance of transgenic tobacco (<i>Nicotiana tabacum</i> L.) to <i>Botrytis cinerea</i> infection was identified. The results show that: Compared with the control, the activities of related defense enzymes SOD (Superoxide dismutase), POD (Peroxidase), PAL (L-phenylalanine ammonia-lyase) and PPO (Polyphenol oxidase) in the over-expressed transgenic tobacco OEA1 and OEA2 increased to different degrees, and increased significantly at different infection time points. The activities of defense enzymes in the interfering strains IEA1 and IEA2 were significantly lower than those in the control strains. The results of resistance level identification showed that the disease spot rate of OEA1 was significantly lower than that of the control line, and the disease spot rate of OEA2 was significantly lower than that of the control line. The plaque rate of the interfering expression line IEA1-IEA2 was significantly higher than that of the control line. It is preliminarily believed that the process related protein <i>GmPR1L</i> can improve the resistance of tobacco to <i>B. cinerea</i>.

ZnO nanoparticles as potential fertilizer and biostimulant for lettuce

Zn is an indispensable nutrient for crops that usually presents low bioavailability. Different techniques have been proposed to improve the bioavailability of Zn, including the use of nanofertilizers. The objective of the study was to evaluate the applications of drench (D) and foliar (F) ZnO nanoparticles (NZnO) compared to those of ionic Zn2+ (ZnSO4) in lettuce. The plants cv. Great Lakes 407 was produced in pots of 4 L with perlite-peat moss (1:1) under greenhouse conditions. The treatments consisted of NZnO applications that replaced the total Zn provided with a Steiner solution, as follows: Zn2+ (100%D) (control); Zn2+ (50%D+50%F); NZnO (100%D); NZnO (50%D+50%F); NZnO (75%D); NZnO (50%D); NZnO (75%F) and NZnO (50%F). Four applications of Zn were made with a frequency of 15 days. 75 days after transplant (DAP), the fresh and dry biomass, chlorophyll a, b, and β-carotene, phenolics, flavonoids, antioxidant capacity, vitamin C, glutathione, H2O2, total protein, and enzymatic activity of PAL, CAT, APX, and GPX were evaluated. The mineral concentrations (N, P, K, Ca, Mg, S, Cu, Fe, Mn, Mo, Zn, Ni, and Si) in the leaves and roots of plants were also determined. The results showed that, compared to Zn2+, NZnO promoted increases in biomass (14–52%), chlorophylls (32–69%), and antioxidant compounds such as phenolics, flavonoids, and vitamin C. The activity of enzymes like CAT and APX, as well as the foliar concentration of Ca, Mg, S, Fe, Mn, Zn, and Si increased with NZnO. A better response was found in the plants for most variables with foliar applications of NZnO equivalent to 50–75% of the total Zn2+ applied conventionally. These results demonstrate that total replacement of Zn2+ with NZnO is possible, promoting fertilizer efficiency and the nutraceutical quality of lettuce.

Nicotiana glauca, a Key Plant for Tomato Growth Enhancement and for the Weed Cynodon dactylon Control

Worldwide, weeds are the costliest category of agricultural pests. They decrease yields and product quality, hence managing them is vital to successful crop cultivation which is the objective of the current study. The present work aims to evaluate the phytotoxicity of the vegetative part and the flowers of Nicotiana glauca on tomato and the weed Cynodon dactylon. Experiments were carried out under field conditions and a number of biochemical and physiological parameters were determined after harvest. The results showed that adding powdered dried flowers to potting soil (in amount of 1%) was the most effective treatment either to inhibit C. dactylon growth or to increase the tomato yield. The stimulations in shoot, root and fresh weight were respectively 35.25%, 328.97%, and 159.04%. It is also remarkable that aqueous extracts of the vegetative part and flowers spray and vegetative part incorporation into soil treatments were effective in stimulating the growth of tomato, but they were less effective in inhibiting the weed growth. In fact, the greatest inhibitions in shoot, rhizomes and fresh weight did not exceed 66.31%, 70.54% and 96.54% after adding powdered dried vegetative part (in amount of 0.6%). The defense strategy developed by lettuce to deal with allelopathic stress could explain the stimulation of tomato growth. Indeed, it increased the production of some metabolites such as polyphenols, flavanols, proanthocyanidins, flavonoids and tannins in addition to proline and carotenoids. An improvement of PAL and TAL activities with a stimulation of the antioxidant activity by increasing DPPH free radicalscavenging activity were also recorded. However, the respiration reduction and the membrane integrity perturbation (demonstrated by an increase in malondialdehyde content and electrolyte leakage) could explain the weed growth inhibition. These findings emphasize that the use of the powdered dried flowers of N. glauca are effective and easily approach to exploit its valuable secondary metabolites either to control C. dactylon or to improve the production of tomato.

Genome-wide studies of PAL genes in sorghum and their responses to aphid infestation

Phenylalanine ammonia-lyase (PAL, EC 4.3.1.25) plays a crucial role in plant adaptation to biotic and abiotic stresses. However, the current knowledge about PAL proteins in sorghum is essentially lacking. Thus, in this study we aimed to analyze the PAL family genes in sorghum using a genome-wide approach and to explore the role of PAL genes in host plant resistance to aphids via SA-mediated defense signaling. Here, we report gene structural features of 8 PAL (SbPAL) genes in sorghum (Sorghum bicolor), their phylogeny, protein motifs and promoter analysis. Furthermore, we demonstrated that the SbPAL genes were induced by sugarcane aphid (SCA) infestation and SbPAL exhibited differential gene expression in susceptible and resistant genotypes. PAL activity assays further validated upregulated expression of the SbPAL genes in a resistant genotype. In addition, exogenous application of SA reduced plant damage and suppressed aphid population growth and fecundity in susceptible genotype, suggesting that those SbPAL genes act as positive regulator of the SA-mediated defense signaling pathway to combat aphid pests in sorghum. This study provides insights for further examination of the defense role of PAL in sorghum against other pests and pathogens.

Effect of Heavy Metal Stress on Phenolic Compounds Accumulation in Winter Wheat Plants.

Heavy metal stress can lead to many adverse effects that inhibit cellular processes at various levels of metabolism, causing a decrease in plant productivity. In response to environmental stressors, phenolic compounds fulfill significant molecular and biochemical functions in plants. Increasing the biosynthesis of phenolic compounds in plants subjected to heavy metal stress helps protect plants from oxidative stress. A pot experiment was carried out to determine the effect of the accumulation of copper (Cu) and lead (Pb) salts at concentrations of 200, 500, and 1000 ppm on seed germination, the activity of enzymes in the phenylalanine ammonia-lyase pathway (PAL) and tyrosine ammonia-lyase (TAL), along with the total phenol and flavonoid contents in seedlings of hybrid Triticum aestivum L. (winter wheat) cultivars. The accumulation of heavy metals, especially Cu, had a negative impact on the seed germination process. The cultivar "Hyacinth" reacted most strongly to heavy metal stress, which was confirmed by obtaining the lowest values of the germination parameters. Heavy metal stress caused an increase in the activity of PAL and TAL enzymes and an increase in the accumulation of phenolic compounds. Under the influence of Cu, the highest activity was shown in cv. "Hyvento" (especially at 200 ppm) and, due to the accumulation of Pb, in cv. "Hyacinth" (1000 ppm) and cv. "Hyking" (200 ppm). The cultivar "Hyking" had the highest content of phenolic compounds, which did not increase with the application of higher concentrations of metals. In other cultivars, the highest content of total phenols and flavonoids was usually observed at the lowest concentration (200 ppm) of the tested heavy metals, Cu and Pb.

Isolation, identification, and biocontrol mechanisms of endophytic Burkholderia vietnamiensis C12 from Ficus tikoua Bur against Rhizoctonia solani

Rice sheath blight is a devastating fungal disease caused by Rhizoctonia solani. Biocontrol utilizing endogenous microorganisms has been considered a safe and sustainable strategy. To obtain a new type of antagonistic bacteria with a high biocontrol effect on rice sheath blight, over 50 endophytic bacteria were isolated from the root of the medicinal plant Ficus tikoua Bur and screened for their antifungal activity by dual culture assay. Among them, strain C12 showed the strongest inhibitory activity against R. solani (inhibition rate 94.78%), and exhibited a broad-spectrum antifungal activity. According to the phylogenetic tree based on 16S rDNA and recA genes, C12 was identified as Burkholderia vietnamiensis, belonging to the Burkholderia cepacia complex, and safe for plants and humans. Through the study on B. vietnamiensis C12, the strain could secrete cell wall degrading enzymes (protease and chitinase), produce IAA, and siderophores, fix nitrogen, and solubilize phosphorus. The bacterial culture filtrate (although treated at 121 °C) of strain C12 and its ethyl acetate extract significantly inhibited the growth of R solani and resulted in distorted hyphae. Moreover, when the extract was 50 μg/mL, 100 μg/mL, 200 μg/mL, and 500 μg/mL, the diameter of mycelium was decreased by 50.44%, 56.43%, 67.27%, and 74.80% respectively, the number of sclerotia was decreased by 85.45%, 90.42%, 96.83%, and 99.22% respectively. Multiple antifungal substances in extracts of C12 were detected through LC-MS. Strain C12 gave a 70.98% reduction in lesion length in a detached inoculated leaf assay. In greenhouse and field tests, strain C12 significantly reduced the disease index of rice sheath blight, and the control efficiency reached 68.75% and 66.52%, respectively. Furthermore, C12 enhanced the resistance of rice to R. solani by increasing the activities of defense enzymes SOD, PAL, POD, CAT, and PPO. The strain also exhibited plant-promoting abilities on rice. The results indicated that B. vietnamiensis C12 had great biocontrol potential and could be used as a candidate strain for green control of rice sheath blight.

Zinc Oxide Nanoparticles and Fe-Modified Activated Carbon Affecting the In Vitro Growth of Date Palm Plantlets cv. Medjool

The survival and growth of in vitro plantlets are still problematic for the date palm; thus, the application of nanotechnology may provide date palm plantlets that develop faster with enhanced growth and biochemical parameters. Moreover, the usage of Fe-modified activated carbon (Fe-AC) prepared from date palm pits instead of activated charcoal (AC) in tissue culture media during the current investigation can be considered an innovative approach. Furthermore, the effect of zinc oxide nanoparticles (ZnO-NPs) and bulk particles (ZnO-BPs) on the rooting and growth of date palm plantlets and on some physiological indices was also investigated. X-ray diffraction, dynamic light scattering, scanning electron microscopy, and transmission electron microscopy were used to characterize Fe-AC and ZnO-NPs. As detected from the characterization, the particle size was 720 nm for Fe-AC and 60 nm for ZnO-NPs. The obtained results indicated that AC significantly enhanced plantlet growth, plantlet height, number of leaves/plantlet, root length, number of roots/plantlet, and the concentrations of IAA, chlorophyll a and chlorophyll b compared with Fe-AC. On the other hand, sugars and phenols concentrations, and POD and PAL activities were highly increased with Fe-AC. There was no significant difference in terms of plant fresh weight (FW), leaf length, leaf width, protein, amino acids, and carotenoids. ZnO nanoparticles significantly improved plant height, leaf length, leaf width, root length, and the concentrations of IAA, chlorophylls a and b, and carotenoids; in contrast, the bulk form increased roots/plantlet, amino acids, and total sugars. Supplying the MS medium with combinations of ZnO-NPs or ZnO-BPs and AC or Fe-AC significantly increased all growth and physiological parameters. Plant height, leaf length, leaf width, root length, and the concentrations of IAA, protein, and chlorophylls a and b significantly increased when ZnO-NPs were combined with AC. Amino acids, total sugars, carotenoids, and phenols concentrations and the activities of POD and PAL increased when ZnO-BPs and Fe-AC were added together.

Elicitation of Bacillus cereus-Amazcala (B.c-A) with SiO2 Nanoparticles Improves Its Role as a Plant Growth-Promoting Bacteria (PGPB) in Chili Pepper Plants.

Agriculture needs to decrease the use of agrochemicals due to their high toxicity and adopt new strategies to achieve sustainable food production. Therefore, nanoparticles (NPs) and plant growth-promoting bacteria (PGPB) have been proposed as viable strategies to obtain better crop yields with less environmental impact. Here, we describe the effect of silica nanoparticles (SiO2-NPs) on survival, antioxidant enzymatic activity, phosphate solubilization capacity, and gibberellin production of Bacillus cereus-Amazcala (B.c-A). Moreover, the effect of the co-application of SiO2-NPs and B.c-A on seed germination, physiological characteristics, and antioxidant enzymatic activity of chili pepper plants was investigated under greenhouse conditions. The results indicated that SiO2-NPs at 100 ppm enhanced the role of B.c-A as PGPB by increasing its phosphate solubilization capacity and the production of GA7. Moreover, B.c-A catalase (CAT) and superoxide dismutase (SOD) activities were increased with SiO2-NPs 100 ppm treatment, indicating that SiO2-NPs act as a eustressor, inducing defense-related responses. The co-application of SiO2-NPs 100 ppm and B.c-A improved chili pepper growth. There was an increase in seed germination percentage, plant height, number of leaves, and number and yield of fruits. There was also an increase in CAT and PAL activities in chili pepper plants, indicating that bacteria-NP treatment induces plant immunity.

Enhanced protection of tomato against Fusarium wilt through biopriming with Trichoderma harzianum

ObjectiveMicrobial priming represents an adaptive strategy to enhance the plant defense against subsequent challenges incited by pathogenic microbes. The aim of the study was to investigate the effect of priming with Trichoderma harzianum (Th) on the induced resistance potential of tomato after challenged with Fusarium oxysporum f. sp. lycopersici (Fol) pathogen. MethodsThis work demonstrated antioxidative and defense related enzyme activities and qRT-PCR to study the resistance mechanisms of tomato plants bioprimed with T. harzianum against Fol pathogen. ResultMicrobial biopriming with T. harzianum resulted into enhanced expression of tomato defense-related genes and was accompanied by increased antioxidative enzymic activities. The study reported that the T. harzianum primed plants showed 2.71-fold higher SOD than control and 1.34-fold (Fol + Th) higher SOD activity compared to Fol challenged plants. In contrast, Fol + Th treated showed 5.87-fold and 1.34-fold higher CAT enzyme activity as compared to control and pathogen exposed plants. T. harzianum bioprimed plants noted 1.47- and 11.47-fold enhanced PPO activity as compared to Fol challenged and controls, respectively. PAL and PO activities were also found higher in T. harzianum primed plants. The qRT-PCR revealed that expression of defense related gene showed higher up-regulation in T. harzianum primed plants as compared to pathogen challenged plants. As compared to control, Fol + Th treated plants also showed higher up-regulation of all the studied genes. ConclusionThe study concluded T. harzianum priming aggravates the plant defense system against the Fol challenged condition and accompanied by higher expression of defense related genes and increased antioxidative activities against subsequent Fol attack.