L-phenylalanine Ammonia-lyase Activity Research Articles

Cell dehydration of intergeneric hybrid induces subgenome-related specific responses.

The aim was to identify subgenome-related specific responses in two types of triticale, that is, of the wheat-dominated genome (WDG) and rye-dominated genome (RDG), to water stress induced in the early phase (tillering) of plant growth. Higher activity of the primary metabolism of carbohydrates is a feature of the WDG type, while the dominance of the rye genome is associated with a higher activity of the secondary metabolism of phenolic compounds in the RDG type. The study analyzed carbohydrates and key enzymes of their synthesis, free phenolic compounds and carbohydrate-related components of the cell wall, monolignols, and shikimic acid (ShA), which is a key link between the primary and secondary metabolism of phenolic compounds. Under water stress, dominance of the wheat genome in the WDG type was manifested by an increased accumulation of the large subunit of Rubisco and sucrose phosphate synthase and a higher content of raffinose and stachyose compared with the RDG type. In dehydrated RDG plants, higher activity of L-phenylalanine ammonia lyase (PAL) and L-tyrosine ammonia lyase (TAL), as well as a higher level of ShA, free and cell wall-bound p-hydroxybenzoic acid, free homovanillic acid, free sinapic acid, and cell wall-bound syringic acid can be considered biochemical indicators of the dominance of the rye genome.

Evaluation of synthesized magnetic nanoparticles and salicylic acid effects on improvement of antioxidant properties and essential oils of Calotropis procera hairy roots and seedlings

Calotropis procera (Aiton) W.T.Aiton presents high levels of medicinally important terpenes and phenolics with antiinflammatory, antimicrobial, and antioxidant properties. The present study aimed to develop a suitable platform for mass production of pharmacological metabolites and improvement of antioxidant activity of C. procera. Motivated by such aim, potential effects of Fe3O4 nanoparticles (Fe3O4 NPs) and salicylic acid (SA) on antioxidant defense response and essential oils in seedlings and hairy roots were investigated. 21-day-old seedlings were treated by five levels of Fe3O4 NPs (0, 50, 100, 150, and 200 mg L−1) and three SA concentrations (0.0, 0.05, 0.1 mM). Moreover, the hairy roots about 2 cm were transferred into MS liquid medium supplemented with the above-mentioned concentrations of Fe3O4 NPs and 0 and 0.01 mM SA. After treatment, total phenolics, flavonoids, flavonol, anthocyanin, activity of polyphenol oxidase and l-phenylalanine ammonia-lyase, ferric-reducing antioxidant power, 2, 2‑diphenyl‑1‑picrylhydrazyl and production of essential oils were analyzed. Results demonstrated that hairy root culture is a powerful alternative for improving and inducing secondary metabolites of C. procera as compared to seedlings. Moreover, it was found that Fe3O4 NPs combined with SA have the more ability than all other treatments to improve antioxidant activity and essential oil in both seedlings and hairy roots. Here, 100 and 200 mg L−1 Fe3O4 NPs combined with 0.01 mM SA had more pronounced impact on induction of pharmacological constituents and antioxidant activity. Results suggest that Fe3O4 NPs and SA in hairy root culture can bring great insights into development in vitro biosynthesis of valuable secondary metabolites. Synthesized magnetic Fe3O4 nanoparticle combined with the salicylic acid in hairy root culture may be considered as a good alternative approach for the mass production of antioxidant and novel pharmacological metabolites of Calotropis procera.

Nanocapsules of oregano essential oil preparation and characterization and its fungistasis on apricot fruit during shelf life

Oregano essential oil nanocapsules (OEO-NPs) were successfully prepared via a complex coacervation method. The results of this study showed that the percentage encapsulation of the OEO-NPs prepared by the best technological process was 88.3%, the loading amount of oregano essential oil (OEO) was 74.36%, and the average particle size was 135 nm. OEO-NPs exhibited better spherical and regular surface structure, higher thermal stability, and slow-release performance. In addition, the 4% OEO-NPs showed better fungistatic effect and reduced decay rate, which compared with the control, 2% and 8% OEO-NPs treatments, during apricot shelf life; 4% OEO-NPs also increased peroxidase, L-phenylalanine ammonialyase, β-1,3-glucanase, catalase and chitinase activities, while reduced the polyphenol oxidase activities during fruit shelf life than that in control. These results provided a new idea for the development of a slow-release fungistatic agent based on plant essential oils. Novelty impact statement Oregano essential oil nanocapsules (OEO-NPs) possessed higher thermal stability and slow-release performance. 4% OEO-NPs showed a better fungistatic effect and reduced apricot fruit decay rate during shelf life. OEO-NPs provided a new idea for the development of green and slow-release fungistatic agent.

Cell wall modification induced by an arbuscular mycorrhizal fungus enhanced cadmium fixation in rice root

The chemistry of root cell wall of rice could be changed by inoculation of arbuscular mycorrhizal fungi (AMF). Hydroponic experiments were conducted to investigate the roles of such changes on cadmium (Cd) uptake and distribution in rice. Results showed that inoculation of AM fungus Rhizophagus intraradices (RI) significantly enhanced (p < 0.05) shoot biomass, plant height and root length of rice, and decreased Cd concentration in shoot and root under Cd stress. Moreover, Cd in root was mainly found in pectin and hemicellulose 1 (HC1) components of root cell wall. Inoculation of RI increased the levels of pectin, HC1 and lignin content, accompanied by the increments of L-phenylalanine ammonia-lyase (PAL) and pectin methylesterase (PME) activities. Results of Fourier transform infrared spectroscopy further showed that more hydroxyl and carboxyl groups in root cell wall were observed in mycorrhizal treatment, compared with control. This study demonstrates that cell wall components could be the locations for Cd fixation, which reduced Cd transportation from root to shoot. Inoculation of AMF may remodel root cell wall biosynthesis and affect the characteristics of Cd fixation. The entering and fixing mechanisms should be further studied.

The Impact of Biopreparations and Phytopathogenic Bacteria of the Pseudomonas Genus on L-Phenylalanine Ammonia-Lyase Activity in Soybean and Lupine Plants

It is known that plant protection against diseases is based mainly on the use of pesticides. These chemicals or their degradation products have a detrimental effect on the environment and human health. Due to this, the search for methods of plant protection that are safe for the environment is becoming increasingly popular. Induction of plant resistance to disease is one of the promising non-chemical ways of protection, in which plant enzymes play a key role. It was shown that in response to pathogen invasion, plants enhance protective properties by inducing the activity of a wide range of enzymes that slow the spread of infection, in particular: peroxidases, β-1,3-glucanases, chitinases, polyphenol oxidases and L-phenylalanine ammonia-lyase (PAL). The aim of the research was to study the change in PAL activity in soybean and lupine plants under conditions of artificial infection with some phytopathogenic bacteria of the Pseudomonas genus and under the action of Ecovital and EPAA-M biological preparations. Methods. PAL activity was determined spectrophotometrically. Changes of soybean (Glycine max) and lupine (Lupinus luteus L.) plants resistance to diseases caused by bacteria of the Pseudomonas genus were evaluated using phytopathological methods. Statistical processing of the research results was performed using MS Excel computer program with Student’s t-test and estimation of least significant difference (LSD). Results. It was found that under conditions of soybean and lupine plants infection with phytopathogenic bacteria of the Pseudomonas genus on the background of pre-sowing seed treatment with Ekovital and EPAA-M biological preparations, composition based on them and synthetic standard – salicylic acid a significant increase in FAL activity in the aboveground and the degree of infectious roots – reducing of plants with pathogens was observed. It has been established that the growth of PAL activity under the condition of infection with phytopathogenic bacteria of the Pseudomonas genus occurs after 2–6 h and lasts up to 7 days from the moment of phytopathogen invasion into the plant. The most increasing of PAL activity was after treatment of seeds with Ecovital and EPAA-M composition – by 38.1–73.3% (Lupinus luteus L.) and 60.4–110% (Glycine max) compared to the control. Treatment with the composition of biological products also helped to reduce the degree of plant damage. PAL activity increasing and reducing the area of soybean and lupine leaves affected surface can indicate the induction of protective reactions in plants. Conclusions. The use of the composition of EPAA-M with the microbial preparation Ecovital contribute to the increase of PAL activity and the formation of resistance to phytopathogenic bacteria of the genus Pseudomonas in Glycine max and Lupinus luteus L. plants.

Multi-walled carbon nanotubes stimulate growth, redox reactions and biosynthesis of antioxidant metabolites in Thymus daenensis celak. in vitro

This research was aimed at determining the effects of multi-walled carbon nanotubes (MWCNTs) on seed germination, seedling growth parameters and secondary metabolite (SM) production of Thymus daenensis in vitro. Seeds were aseptically cultured in Murashige and Skoog medium (MS) with various concentrations of MWCNTs (0, 125, 250, 500, 1000 and 2000 μg ml−1). Seed germination and morphological changes in seedlings were measured. The measurements were aimed at quantifying the total phenolic contents (TPC) and flavonoids (TFC), antioxidant activities and the activity of polyphenol oxidase (PPO), l-phenylalanine ammonia-lyase (PAL), dehydrogenase (DHA) and peroxidase enzyme (POD) of the seedling extract. Seedling biomass and seedling height grew significantly as the MWCNTs level increased. The biomass and height peaked at 250 μg ml−1 (0.41 ± 0.01 gr FW, 5.99 ± 0.55 cm) and then rapidly decreased to 0.040 ± 0.1 gr FW and 1.42 ± 0.24 cm in response to 1000 μg ml−1, 30 days after the treatment. Additionally, SM and the analyses of enzyme activity revealed that the highest amounts of TPC (6.70 ± 0.06 mg GAE g−1 DW), TFC (8.19 ± 0.01 mg QUE g−1 DW), antioxidant activities (73.88 ± 0.47%) and maximum PAL activity (1.25 ± 0.08 mM cm g−1 FW) were detected in plants grown on MS media fortified with 250 μg ml−1 MWCNTs. The results reveal that MWCNTs in low doses (250 μg ml−1) can encourage the production of biomass, elicit more SM from seedlings and enhance the biosynthesis of antioxidants. TEM images showed that MWCNTs could cross the plant cell wall and enter the cellular cytoplasm.

The accumulation of phenolic compounds and increased activities of related enzymes contribute to early defense against walnut blight

Xanthomonas arboricola pv. juglandis (Xaj) is the causal pathogen of walnut blight. This work evaluates the correlations between selected biochemical responses to Xaj and the degree of blight sensitivity in ten genotypes. Activity of superoxide dismutase (SOD), peroxidase (POX), l-phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO), and content of phenolic compounds and malondialdehyde (MDA) significantly increased in all walnut genotypes after inoculation by Xaj while Catalase (CAT) activity varied between genotypes. Genotype's blight sensitivity was correlated with relative increases in phenolic compound content and PAL, PPO and POX activity at the initial stage of inoculation. The results show both similarities and distinct features in defense response in genotypes, suggesting that the metabolism of phenolic compounds may play a more important role in initial stages of inoculation than originally thought.

Effect of foliar bio-fertilization on growth and biochemical parameters of olive trees at flowering

Growth and biochemical parameters of leaves, flower buds and flowers of olive (Olea europaea L. cv. Chemlali) treated by foliar biofertilization (T0: untreated trees; T1: rich in nitrogen (N), phosphorus (P), potassium (K); T2: rich in calcium (Ca); T3: application of T1 and T2) were analyzed during the flowering stage. The results showed that T1 resulted in higher contents of leaf N, K, and Na. T1 and T3 resulted in an increase of pigment concentration in leaves. All foliar treatments affected negatively the contents of total polyphenols and orthodiphenols in leaves and flower buds. Lower amounts of individual phenolic compounds were detected in the leaves under all foliar bio-fertilizations and in flower buds of olive trees sprayed with T2 and T3. This decrease is explained by the lower enzymatic activity of l-phenylalanine ammonia-lyase. In flowers, T1 exhibits the highest levels of total polyphenols, o-diphenols, and individual phenolic compounds compared to T0.

Phytochemical changes in mango fruit in response to Alternaria alternata infection

Changes in mango fruit quality, malondialdehyde content, and enzymatic activities in response to pathogen Alternaria alternata infection were studied. A. alternata significantly affected the appearance of mango fruit at 5 and 7 days after treatment (DAT). The quality of pathogen-infected fruit first showed a significant decrease in titratable acidity and vitamin C content and a significant increase in pH since 3 DAT. The malondialdehyde content was higher than that in the untreated controls at 3 and 7 DAT. The enzyme activities of ascorbate peroxidase and polyphenol oxidase showed significant increases since 3 DAT. Significant increases in l-phenylalanine ammonia-lyase and superoxide dismutase activities were observed at 7 DAT. These results indicate that A. alternata infection first significantly affects some biochemical constituents and enzyme activities in mango fruit since 3 DAT and that there was no significant effect on appearance until 5 DAT.

Accumulation of Phenolic Compounds at the Initial Steps of Ontogenesis of Fagopyrum esculentum Plants That Differ in Their Ploidy Levels

Plants of buckwheat Fagopyrum esculentum possessing diploid and tetraploid genotypes were studied at the initial ontogenetic stages. They were compared in their morphophysiological characteristics, accumulation of phenolic compounds (including their main classes—phenylpropanoids and flavonoids), and activity of L-phenylalanine ammonia-lyase. An apparent resemblance in morphophysiological characteristics of seedlings was found between the two specimens, but diploid plants tended to faster linear growth than tetraploid ones. Differences in the accumulation of phenolic compounds in the hypocotyl and cotyledonous leaves were revealed. In most cases, in the course of seedling growth, the changes in phenylalanine ammonialyase activity did not correlate with the changes in the levels of these secondary metabolites. The effects of gene dosage were established towards accumulation of phenylpropanoids and anthocyanins in hypocotyls of seedlings and flavonoid accumulation in cotyledonous leaves. It is concluded that buckwheat seedlings with a tetraploid genotype have higher capacity than diploid seedlings for biosynthesis of phenolics.

Biofortification (Se): Does it increase the content of phenolic compounds in virgin olive oil (VOO)?

Extra-Virgin Olive Oil (EVOO) is a fundamental component of the Mediterranean diet and it may contain several anti-oxidant substances, such as phenols. Previous research has shown that this food may be enriched in phenols by spraying a sodium-selenate solution (100 mg L-1 Se) onto the crop canopy before flowering. The aim of this research was to evaluate the effect of this Se-fertilization before flowering (cv. Leccino) on the phenolic profile of EVOOs, and test to what extent such effects depend on the weather pattern, as observed in two contrasting experimental seasons (2013 and 2014). Results showed that Se-fertilisation enriched EVOOs both in selenium (up to 120 μg kg-1) and in phenols (up to 401 mg kg-1). This latter enrichment was related to an increase in PAL (L-Phenylalanine Ammonia-Lyase) activities and it was largely independent on the climatic pattern. Considering the phenolic profile, oleacein, ligustroside, aglycone and oleocanthal were the most affected compounds and were increased by 57, 50 and 32%, respectively. All these compounds, especially oleacein, have been shown to exert a relevant anti-oxidant activity, contributing both to the shelf-life of EVOOs and to positive effects on human health. It is suggested that Se-fertilisation of olive trees before flowering may be an interesting practice, particularly with poor cultivars and cold and rainy weather patterns, which would normally lead to the production of EVOOs with unfavourable phenolic profile.

Role of cellular NADP + /NADPH ratio in the acclimative mechanism of two common bean cultivars toward salt stress

This study is aimed to evaluate the adaptive mechanism in two common bean ( Phaseolus vulgaris L.) cultivars, cv. Bronco and cv. Paulista subjected to different concentrations of NaCl (0, 25, 50 and 75 mM). Salt treatments resulted in a significant decrease in the fresh and dry biomasses of shoots and roots as well as leaf relative water content (RWC) in both bean cultivars. Salt stress determines a diversion of plant metabolism towards the synthesis of phenolics, proline and trigonelline (TRG) components together with an increase in the NADP + /NADPH ratio. This increase was accompanied with a significant increase in glucose-6-phosphate dehydrogenase (G-6-PDH) and L-phenylalanine ammonia-lyase (PAL) activities in both bean cultivars. Furthermore, increasing NaCl levels induced oxidative stress measured in terms of malondialdehyde and H 2 O 2 contents. Salt stress triggered an increase in guaiacol peroxidae (GPX) activity in both bean cultivars, whereas polyphenol oxidase (PPO) activity increased only in Bronco plants. The results are discussed in the light of possible roles and regulation of cellular redox potential (NADP + /NADPH) in the maintenance of acclimative mechanism in the two common bean cultivars grown under NaCl stress.

The Effect of Bacillus amyloliquefaciens subsp. plantarum IMV B-7524 Strain Exometabolites on the Induction of Defense Reactions in Winter Wheat Plants

To study the effect of antibiotic exometabolites of Bacillus amyloliquefaciens subsp. plantarum IMV B-7524 strain on the induction of defense responses in young plants of winter wheat. Microbiological, biochemical, phytopathological, statistical. It was found that, when pre-watering winter wheat plants with salicylic acid, the cell-free culture supernatant and lipopeptide fraction of IMV B-7524 strain exometabolites during the further infection with phytopathogen Bipolaris sorokiniana, the damaged surface area of leaves decreased more than 10 times compared to the control. It was shown that in the roots and shoots of winter wheat plants L-phenylalanine ammonia-lyase (PAL) activity increased about 3 times in 2 hours after treatment. Reduction of the damaged surface area of leaves by the action of fungal phytopathogen and change of PAL activity in plants indicate the induction of defense responses under the influence of antibiotic exometabolites of B. amyloliquefaciens subsp. plantarum IMV B-7524 strain.

Effects of low-temperature hardening on the biochemical response of winter oilseed rape seedlings inoculated with the spores of Leptosphaeria maculans

AbstractThe aimof the study was to assess the effects of low-temperature hardening (2◦C) on the biochemical compounds and processes that can increase resistance of winter rape to inoculation with Leptosphaeria maculans spores. The study involved an evaluation of the entire pool of phenolic compounds, L-phenylalanine ammonia lyase (PAL) activity, excitation intensity for blue and green fluorescence, catalase (CAT) activity, respiration intensity and heat emission from leaf tissues. All the measurements were performed 24 and 72 hours after the inoculation. Low-temperature hardening, which preceded the inoculation of rape seedlings with spores of L. maculans, caused a significant increase in CAT activity and the level of phenolic compounds. The observed changes in PAL activity reflected the changes in phenolics content. The hardened plants showed a significantly higher intensity of blue fluorescence excitation at 24 and 72 hours after the inoculation, as compared to the non-hardened seedlings. Increased content of phenolic compounds and PAL and catalase activity triggered by the temperature of 2◦C and maintained for 24 hours after the inoculation, may confirm the stimulating effect of the hardening temperature. Intensified emission of blue fluorescence indicating saturation of a cell wall with phenolic compounds makes the cell wall structure less stretchy, more tight and leakproof, and thereby hinders fungal growth through plant tissue.

Multi-walled carbon nanotubes stimulate callus induction, secondary metabolites biosynthesis and antioxidant capacity in medicinal plant Satureja khuzestanica grown in vitro

The present study was carried out to explore the potential effects of multi-walled carbon nanotubes (MWCNTs) on callus induction and secondary metabolism in Satureja khuzestanica. Leaf segments were aseptically cultured in B5 basal medium with different MWCNTs concentrations (0, 25, 50, 100, 250 and 500μgml−1). The calli morphogenic responses were measured and the contents of phenolics, flavonoids, rosmarinic acid (RA), caffeic acid (CA), and the activity of polyphenol oxidase (PPO), l-phenylalanine ammonia-lyase (PAL) and peroxidase (POD) were quantified. Moreover, antioxidant activities of calli extract were assayed. Calli growth improved significantly with the increase of MWCNTs concentration, peaked at 50μgml−1, and then followed a rapid decrease at 500μgml−1. However, metabolic effects observed following exposure to MWCNTs particularly at 100μgml−1 tended to be more pronounced than all other treatments, exhibiting significant induction of antioxidant activity with the lowest IC50 value. Maximum oxidative stress index (H2O2) and the highest PPO and POD activities were observed on the media treated with 500μgml−1 MWCNTs. Our findings suggest for the first time that use of MWCNTs at specific levels could act as a novel elicitor for in vitro biosynthesis of valuable secondary metabolites and antioxidant drugs.

Physiological Responses of Two Moss Species to the Combined Stress of Water Deficit and Elevated Nitrogen Deposition. I. Secondary Metabolism

Premise of research. It has been well documented that secondary metabolites in mosses can protect mosses from pathogen or herbivore attacks, but their functions in abiotic stress are poorly understood. Thus, we have investigated effects of water deficit and high nitrogen (N) on secondary metabolism in two moss species.Methodology. KNO3 or NH4Cl was supplied to Pogonatum cirratum subsp. fuscatum and Hypnum plumaeforme at rates of 20–60 kg N hm−2 for 1 yr, water was then withheld for 12 d, and finally a 10-d recovery treatment was applied. Indexes of oxidative stress (superoxide dismutase [SOD], malondialdehyde [MDA]) and secondary metabolism were determined after the water-withholding and recovery treatments, respectively.Pivotal results. Both ammonium and nitrate supply stimulated SOD activity and MDA accumulation as well as the synthesis of phenylpropanoids, triterpenes, and total alkaloids. Water-deficit stress induced oxidative stress in both moss species, and N application exacerbated the oxidative stress. Water deficit inhibited SOD and L-phenylalanine ammonia-lyase activities and changed their phenylpropanoid profiles (with interspecific differences). Triterpene accumulation was stimulated by water deficit in H. plumaeforme (but not in P. cirratum), while alkaloid accumulation was stimulated in both mosses. After the 10-d recovery period, the N treatments generally still had significant effects on SOD activity and secondary metabolite contents, and water deficit still had effects on contents of some phenolics and alkaloids. However, SOD activity in the water-deficit-treated P. cirratum samples was restored after recovery, indicating that it may play an important role in recovery from stress induced by water deficit.Conclusions. The secondary metabolism of both mosses is intimately linked to their antioxidant mechanisms. Phenylpropanoids, triterpenes, and alkaloids may mark moss responses to stress and therefore present a useful method for environmental monitoring in the mosses.

Effects of low-temperature stress on secondary metabolism in mosses exposed to simulated N deposition

Background: Both nitrogen deposition and low-temperature stress (LTS) affect the secondary metabolism of plants, but few were known about the responses of secondary metabolism to combined LTS and nitrogen supply, especially for mosses.Aims: To investigate the effects of LTS on secondary metabolism in two mosses, Pogonatum cirratum subsp. fuscatum and Hypnum plumaeforme, under varied nitrate or ammonium supply rates.Methods: Indices of oxidative stress and secondary metabolism in two mosses that were subjected to different N application and LTS treatment were measured both before and after a period of 10-day recovery.Results: LTS-induced oxidative stress was exacerbated by combined N application. LTS inhibited superoxide dismutase (SOD) activity in P. cirratum subsp. fuscatum, but in H. plumaeforme SOD activity it was insensitive. N application induced increases in L-phenylalanine ammonia-lyase activity in both mosses, but the consequent changes in phenylpropanoid profiles in the mosses differed. LTS only changed the phenylpropanoid profiles. Levels of triterpenes were also affected by both N supply and LTS. In addition, levels of some secondary metabolites remained relatively high after 10-day recovery from LTS.Conclusions: N supply altered the responses of secondary metabolism to LTS. Some secondary metabolites may be stress memory substances associated with LTS of the mosses, with between-species differences.

The effect of cold on the response of Brassica napus callus tissue to the secondary metabolites of Leptosphaeria maculans

The fungus Leptosphaeria maculans that causes blackleg can attack winter rape throughout the entire growing season. Therefore, appropriate treatments were designed to simulate environmental factors that may occur under field conditions. The callus tissue of winter rape was treated with abiotic stress in the form of cold (2 °C) and temperature change (2/20 °C and 20/2 °C), and biotic stress in the form of secondary metabolites of L. maculans. The following parameters were analyzed: total phenolics, the activity of l-phenylalanine ammonia lyase (PAL), catalase, respiration intensity, heat emission, and metabolic activity determined by means of 2,3,5-triphenyl-tetrazolium chloride (TTC) assay. Additionally, the changes in the electrical potential, known as a sensitive indicator of biochemical changes in the callus tissue, were measured. The obtained results seem to indicate rather increased stress, caused by temperature (2 or 20 °C) or its changes (2/20 °C, 20/2 °C) and the secondary metabolites of L. maculans than a cross reaction. The factor that most strongly affected the metabolism of winter rape callus tissue was the temperature change, which masked the changes caused by the fungal secondary metabolites or intensified their adverse effects. The only parameters that could be regarded as reliable indicators of the callus tissue response to the elicitation with secondary metabolites of L. maculans were catalase activity and respiration intensity. Additionally, a protective function of low temperature involved a reduction in catalase activity, resulting in increased level of reactive oxygen species (ROS), key molecules inducing the defense mechanisms during pathogenesis. Only the changes in l-phenylalanine ammonia lyase (PAL) activity and the accompanying changes in the content of phenolic compounds can be considered as beneficial effects of low temperature (2 °C) on a more efficient callus acclimation to the biotic stress.

Seed biopriming with drought tolerant isolates ofTrichoderma harzianumpromote growth and drought tolerance inTriticum aestivum

Green house study was aimed to investigate the effect of seed biopriming with drought tolerant isolates of Trichoderma harzianum, viz. Th 56, 69, 75, 82 and 89 on growth of wheat under drought stress and to explore the mechanism underlying plant water stress resilience in response to Trichoderma inoculation. Measurements of relative water content, osmotic potential, osmotic adjustment, leaf gas exchange, chlorophyll fluorescence and membrane stability index were performed. In addition, analysis of the phenolics, proline, lipid peroxidation and measurements of phenylalanine ammonia-lyase activity were carried out. Seed biopriming enhanced drought tolerance of wheat as drought induced changes like stomatal conductance, net photosynthesis and chlorophyll fluorescence were delayed. Drought stress from 4 to 13 days of withholding water induced an increase in the concentration of stress induced metabolites in leaves, while Trichoderma colonisation caused decrease in proline, malondialdehyde (MDA) and hydrogen peroxide (H2O2), and an increase in total phenolics. A common factor that negatively affects plants under drought stress conditions is accumulation of toxic reactive oxygen species (ROS), and we tested the hypothesis that seed biopriming reduced damages resulting from accumulation of ROS in stressed plants. The enhanced redox state of colonised plants could be explained by higher l-phenylalanine ammonia-lyase (PAL) activity in leaves after 13 days of drought stress in Trichoderma treated plants. Similar activity was induced in untreated plants in response to drought stress but to a lower extent in comparison to treated plants. Our results support the hypothesis that seed biopriming in wheat with drought tolerant T. harzianum strains increased root vigour besides performing the process of osmoregulation. It ameliorates drought stress by inducing physiological protection in plants against oxidative damage, due to enhanced capacity to scavenge ROS and increased level of PAL, a mechanism that is expected to augment tolerance to abiotic stresses.

Screening and Identification of Pigmental Yeast Producing L-phenylalanine Ammonia-Lyase and Their Physiological and Biochemical Characteristics

The results of the analysis of DNA sequences encoding L-phenylalanine ammonia-lyase (PAL) synthesis, performed to obtain universal primers complementary to conserved regions of the pal gene, are presented in the article. The fragment of pal gene was amplified in organisms under study. Nucleotide sequence of the pal gene in microorganisms exhibiting L-phenylalanine ammonia-lyase activity was determined by DNA sequencing. The results of its comparison with the corresponding sequences of known species are presented. Phenotypic characteristics and biochemical properties of selected cultures were studied. An investigation aimed to choose a superproducer strain of L-phenylalanine ammonia-lyase was conducted. It was found that L-phenylalanine ammonia-lyase synthesis was the most active in the following strains: Aureobasidium pullulans Y863, Rhodosporidium infirmominiatum Y1569, Candida glabrata Y2813, Candida maltose Y242, Debaryomyces robertsiae Y3392, Rhodosporidium diobovatum Y1565, Rhodotorula lactose Y2770, Saccharomyces cerevisiae Y1127, Tilletiopsis washingtonensis Y1650, Torulopsis apicola Y566, Tremella foliacea Y1624, Rhodotorula rubra Y1193, and Debaryomyces castellii Y968. This allows recommending them for further research aimed to obtain the enzyme preparation of L-phenylalanine ammonia-lyase.