Synthesis Of Secondary Products Research Articles

Secondary metabolites responses of plants exposed to ozone: an update.

Tropospheric ozone (O3) is a secondary pollutant that causes oxidative stress in plants due to the generation of excess reactive oxygen species (ROS). Phenylpropanoid metabolism is induced as a usual response to stress in plants, and induction of key enzyme activities and accumulation of secondary metabolites occur, upon O3 exposure to provide resistance or tolerance. The phenylpropanoid, isoprenoid, and alkaloid pathways are the major secondary metabolic pathways from which plant defense metabolites emerge. Chronic exposure to O3 significantly accelerates the direction of carbon flows toward secondary metabolic pathways, resulting in a resource shift in favor of the synthesis of secondary products. Furthermore, since different cellular compartments have different levels of ROS sensitivity and metabolite sets, intracellular compartmentation of secondary antioxidative metabolites may play a role in O3-induced ROS detoxification. Plants' responses to resource partitioning often result in a trade-off between growth and defense under O3 stress. These metabolic adjustments help the plants to cope with the stress as well as for achieving new homeostasis. In this review, we discuss secondary metabolic pathways in response to O3 in plant species including crops, trees, and medicinal plants; and how the presence of this stressor affects their role as ROS scavengers and structural defense. Furthermore, we discussed how O3 affects key physiological traits in plants, foliar chemistry, and volatile emission, which affects plant-plant competition (allelopathy), and plant-insect interactions, along with an emphasis on soil dynamics, which affect the composition of soil communities via changing root exudation, litter decomposition, and other related processes.

Effect of the plant probiotic bacteria on terpenoid indole alkaloid biosynthesis pathway gene expression profiling, vinblastine and vincristine content in the root of Catharanthus roseus.

Catharanthus roseus is the sole resource of vinblastine and vincristine, two TIAs of great interest for their powerful anticancer activities. Increasing the concentration of these alkaloids in various organs of the plant is one of the important goals in C. roseus breeding programs. Plant probiotic bacteria (PBB) act as biotic elicitors and can induce the synthesis of secondary products in plants. The purpose of this research is to study the effects of PBB on expression of the TIA biosynthetic pathway genes and the content of alkaloids in C. roseus. The individual and combined effects of P. fluorescens strains 169 and A. brasilense strains Ab-101 was studied for expression of the TIA biosynthetic pathway genes (G10H, DAT, T16H and CrPRX) using qRT-PCR and the content of vinblastine and vincristine using HPLC method in roots of C. roseus. P. fluorescens. This drastically increased the content of vinblastine and vincristine alkaloids, compared to the control in the roots, to 174 and 589 (µg/g), respectively. Molecular analysis showed bacterium significantly increased the expression of more genes in the TIA biosynthetic pathway compared to the control. P. fluorescens increased the expression of the final gene of the biosynthetic pathway (CrPRX) 47.9 times compared to the control. Our findings indicate the correlation between transcriptional and metabolic outcomes. The same was true for A. brasilense. It can be concluded that seed treatments and seedling root treatments composed of naturally occurring probiotic bacteria are likely to be widely applicable for inducing enhanced alkaloid contents in medicinal plants.

Comparative Transcriptome Analysis of Streptomyces nodosus Mutant With a High-Yield Amphotericin B.

Antibiotics play an important role in human health. Most antibiotics are derived from microbial secondary metabolites. Amphotericin is a polyene macrolide antibiotic synthesized by Streptomyces nodosus. S. nodosus ZJB2016050 with high-yield amphotericin B (AmB) was obtained by traditional mutagenesis using S. nodosus ATCC14899 as the original strain. The differences in the characterization of the two strains were found in color, mycelium morphology, and AmB yield. Subsequent comparative transcriptome explained the yield differences between the two strains. Pathways including the carbohydrate metabolic pathway and the secondary product synthesis pathway were targeted. The upregulation of glucokinase, phosphoglycerate mutase, and pyruvate dehydrogenase accelerates the consumption of glucose and has great effects on the accumulation of precursors. One of the competitive secondary metabolites of the polyketone synthetase (PKS) II type sapromomycin analog synthesis gene cluster was downregulated, which competes for malonyl-CoA. Five PKS modules (except for the first module amphA) of the amphotericin synthetic gene cluster in the high-yielding strain were downregulated, which resulted in the total amphotericin A (AmA) and AmB of S. nodosus ZJB2016050 being less than that of the wild-type S. nodosus ATCC14899. Combined with gene differential expression in the pentose phosphate pathway and the reaction mechanism of the ER5 domain, the reason that S. nodosus ZJB2016050 preferred to synthesize AmB was probably related to intracellular reduction.

Use of Schizosaccharomyces pombe and Torulaspora delbrueckii strains in mixed and sequential fermentations to improve red wine sensory quality

One of the main opportunities in the use of non-Saccharomyces yeasts is its great intraspecific variability in relation to the synthesis of secondary products of fermentation. Thus, mixed or sequential fermentation with non-Saccharomyces can increase the synthesis of certain metabolites that are important for colour stability, such as acetaldehyde and pyruvic acid (vitisin precursors) or vinylphenols (vinylphenolic pyranoanthocyanin precursors). Furthermore, the selection and use of non-Saccharomyces yeast strains with good yields in the production of certain volatile compounds (ethyl lactate, 2,3-butanediol, 2-phenylethyl acetate), with limited formation of higher alcohols, is a way to improve the aromatic profile of red wine. The main aim of this work was to evaluate the influence of sequential and mixed fermentations with Schizosaccharomyces pombe and Torulaspora delbrueckii strains on red wine's sensory quality. Anthocyanins and aromatic profiles, as well as glycerol and organic acid content, were analysed in the red wines obtained. Results show that, in general, mixed fermentations can promote an increment in polyols synthesis, while sequential fermentations can enhance the herbaceous aroma. Moreover, the use of T. delbrueckii in mixed fermentations allowed an increase to the fruity character of red wine. The use of S. pombe in sequential fermentations increased the stability of the colouring matter by favouring vitisins and vinylphenolic pyranoanthocyanin formation.

Functional state modelling approach validation for yeast and bacteria cultivations

In this paper, the functional state modelling approach is validated for modelling of the cultivation of two different microorganisms: yeast (Saccharomyces cerevisiae) and bacteria (Escherichia coli). Based on the available experimental data for these fed-batch cultivation processes, three different functional states are distinguished, namely primary product synthesis state, mixed oxidative state and secondary product synthesis state. Parameter identification procedures for different local models are performed using genetic algorithms. The simulation results show high degree of adequacy of the models describing these functional states for both S. cerevisiae and E. coli cultivations. Thus, the local models are validated for the cultivation of both microorganisms. This fact is a strong structure model verification of the functional state modelling theory not only for a set of yeast cultivations, but also for bacteria cultivation. As such, the obtained results demonstrate the efficiency and efficacy of the functional state modelling approach.

Post-eruptive process and products of volcanic rock alteration (transformation and synthesis of secondary products)

The conditions of transformation of the primary material of extrusive rocks and the synthesis of secondary products during post-eruptive processes have been considered using the example of three large areas of presentday volcanism and hydrothermal activity in Kamchatka, viz., the Great Tolbachik Fissure Eruption of 1975–1976 (GTFE), the Karymskii Volcanic Center (eruption of 1996 in Lake Karymskii), and the Uzon volcanic-hydrothermal system. Post-eruptive transformation of rocks causes volcanic-hydrothermal lithogenesis and low-middle-temperature mineralization in areas of present-day contrast (basalt-andesite) volcanism in zones of crustal extension. Based on the permanent presence of a wide range of acid rocks, such as dacites, rhyolites, and pumices in the areas of Holocene basalt volcanism of Kamchatka, we concluded that in conditions of pre-rift crustal extension, acid volcanism is preceded by deep-seated differentiation (similar to liquation) of primary mantle melts with separation of fluids enriched in ore-forming elements, first of all Cu, Zn, Pb, As, Sb, and Hg. During volcanogenic-hydrothermal lithogenesis in the discharge areas of those fluid systems, the destruction and replacement of primary minerals of igneous rocks and formation of complex-composition metasomatites take place. Clay minerals are major components of metasomatites in subaqueous conditions. The role of microbiota in processes of volcanogenic-hydrothermal lithogenesis and occurrences of local mineralization was studied.

Chemical diversity and defence metabolism: how plants cope with pathogens and ozone pollution.

Chemical defences represent a main trait of the plant innate immune system. Besides regulating the relationship between plants and their ecosystems, phytochemicals are involved both in resistance against pathogens and in tolerance towards abiotic stresses, such as atmospheric pollution. Plant defence metabolites arise from the main secondary metabolic routes, the phenylpropanoid, the isoprenoid and the alkaloid pathways. In plants, antibiotic compounds can be both preformed (phytoanticipins) and inducible (phytoalexins), the former including saponins, cyanogenic glycosides and glucosinolates. Chronic exposure to tropospheric ozone (O3) stimulates the carbon fluxes from the primary to the secondary metabolic pathways to a great extent, inducing a shift of the available resources in favour of the synthesis of secondary products. In some cases, the plant defence responses against pathogens and environmental pollutants may overlap, leading to the unspecific synthesis of similar molecules, such as phenylpropanoids. Exposure to ozone can also modify the pattern of biogenic volatile organic compounds (BVOC), emitted from plant in response to herbivore feeding, thus altering the tritrophic interaction among plant, phytophagy and their natural enemies. Finally, the synthesis of ethylene and polyamines can be regulated by ozone at level of S-adenosylmethionine (SAM), the biosynthetic precursor of both classes of hormones, which can, therefore, mutually inhibit their own biosynthesis with consequence on plant phenotype.

GROUP 13 CLUSTER CHEMISTRY: ORGANOGALLIUM AND -INDIUM SUBHALIDES AND RADICALS

Organogallium or-indium subhalides are easily available by the halogenation of the corresponding tetrahedral clusters E 4 [C(SiMe 3 ) 3 ] 4 . Three types of compounds are formed that retain the tetrahedral arrangement of In atoms or give chains with two or three Ga or In atoms connected by E─E bonds. These subhalides are suitable starting compounds for the synthesis of secondary products containing the elements in low oxidation states. Carboxylato derivatives or transition metal complexes were obtained on such a route. A persistent radical anion was formed on electron transfer to Ga 9 (CMe 3 ) 9 .

Effect of Oxygen Limitation on β‐Lactamase Production

AbstractThe dissolved oxygen concentration (DO) is an important variable in aerobic fermentations. Precise control of the DO is critical in fermentation processes for the investigation of the best conditions for secondary product formation. Oxygen limitation conditions have been known to enhance the synthesis of secondary products. An adaptive pole placement control that maintains a constant sheer environment is applied to Bacillus subtilis fermentation for the production of β‐lactamase. Auto Regressive eXogeneous (ARX) input models are used for the control, and supervision and coordination techniques are applied to improve the control performance. The effect of DO level on the productivity of β‐lactamase under oxygen‐limited conditions is assessed.

Pyrimidine metabolism and secondary product formation; biogenesis of albizziine, 4-hydroxyhomoarginine and 2,3-diaminopropanoic acid

In relation to the biogenesis of pyrimidine-derived secondary products, the relative activities and substrate specificities of the enzymes of pyrimidine metabolism were determined in extracts of seedlings from a number of leguminous species. Carbamoyl phosphate synthetase (CPSase) and aspartate transcarbamoylase (ATCase) were 4 to 6 × more active, and 5′-nucleotidase and uridine hydrolase were 2 to 3 × more active in the secondary metabolite producing species examined. As it was also confirmed that UMP is the most effective nucleotide inhibitor of ATCase activity, these relatively high rates of hydrolysis of UMP to uracil would lessen effective negative feedback control of pyrimidine synthesis in the secondary metabolite producers and further increase the availability of uracil for secondary metabolism. The key enzyme of pyrimidine catabolism, NADPH-dependent dihydrouracil dehydrogenase was shown to use uracil, thymine, lathyrine and 5-aminouracil as substrates and its activity was 2 to 3 × higher in those species not yielding pyrimidine secondary products. This observation is consistent with the diversion, in the secondary product-forming plants examined, of significant amounts of uracil away from catabolism and into secondary product synthesis. The dihydrouracil dehydrogenase of Albizia julibrissin exhibited higher activity with 5-aminouracil as substrate than with uracil or thymine. Dihydropyrimidinase, the next enzyme in the catabolic pathway, was extracted from the various species and shown to use 5,6-dihydrouracil 5,6-dihydrothymine and 5-amino-5,6-dihydrouracil as substrates. Using a NADPH-regenerating system, the combined action of the two enzymes, dihydrouracil dehydrogenase and dihydropyrimidinase, was shown to produce 4-hydroxyhomoarginine from lathyrine. This was identified by co-chromatography and electrophoresis with authentic samples of 4-hydroxy-homoarginine. Preparations of β-ureidopropionase, the third enzyme in the catabolic pathway, were obtained from seedlings of Pisum sativum and shown to hydrolyse N-carbamoyl- β-alanine to 3-aminopropanoic acid, and N-carbamoyl-2-methyl-3-aminopropanoic acid to 3-amino-2-methylpropanoic acid. Additionally, the preparations from P. sativum and A. julibrissin hydrolysed albizziine to 2,3-diaminopropanoic acid, identified by co-chromatography and electrophoresís with authentic samples. It is concluded that there is a greater production and diversion of uracil into secondary product formation in the plants producing these compounds than in those that do not. In the non-producing plants, there is a more active catabolism of uracil. With A. julibrissin, degradation of 5-aminouracil by the pyrimidine catabolic process was shown to yield the non-protein amino acids albizziine and 2,3-diamino-propanoic acid. In Lathyrus tingitanus, this process demonstrably produces 4-hydroxyhomoarginine from lathyrine. The observations described are consistent with the view that production of pyrimidine-derived secondary products is attributable to the operation of detoxication processes for bioactive pyrimidines.

Metabolic engineering of plant secondary products.

Plants interact with their environment by producing a diverse array of secondary metabolites. Many of these compounds are valued for their medicinal, industrial or agricultural properties. Other secondary products are toxic or otherwise undesirable and can reduce the commercial value of crops. Gene transfer technology offers new opportunities to modify directly plant secondary product synthesis through metabolic engineering. This article reviews some of the strategies which have been used to increase or decrease the synthesis of specific plant metabolites, as well as methods for expanding the biosynthetic capabilities of individual species.

Enhancement of phytoalexin accumulation in cultured plant cells by oxalate

Oxalate (0.2–2.0 mM), a compound which induces systemic resistance, can enhance secondary product synthesis 10-fold in cotton cell suspension cultures. To accomplish this, cells require induction with a low level (10 μ of protein per 15 ml incubation) of elicitor from Verticillium dahliae. In the presence of oxalate, these minimal concentrations of elicitor required to induce phytoalexin formation did not have any necrotic effect on the growth of the cotton cultures. Even at higher concentrations of elicitor (80 μg of protein per 15 ml incubation), oxalate was able to reduce the detrimental effect of elicitor on cell suspension growth rates indicating oxalate may have a direct effect on growth. Therefore, in cotton cell suspension cultures the addition of an enhancer of elicitor-induced phytoalexin formation allows optimum stimulation of secondary metabolite formation without affecting cell mass accumulation.

Phosphate feeding to permit growth while maintaining secondary product synthesis

Summary. Maintaining high metabolic activities for extended periods by feeding small amounts of the growth limiting nutrient was examined for the production of cycloheximide by Streptomyces griseus. Batch studies indicated that increased initial phosphate levels led to increased cell concentrations, stimulated glucose utilization, and over a limited range (<0.6 g/1 KH2PO4) did not adversely affect cycloheximide production rates. Semi-continuous phosphate feeding was observed to permit limited cell growth, and to enhance metabolic activities (i. e. glucose utilization). The effect of semi-continuous phosphate feeding on antibiotic production depended on the feed rate, with high feed rates suppressing production.

Relationship between Agrobacterium rhizogenes transformed hairy roots and intact, uninfected nicotiana plants

Hairy root cultures were obtained following infection of a range of Nicotiana species with Agrobacterium rhizogenes. Such cultures synthesized alkaloids in amounts which closely reflected, in both qualitative and quantitative terms, the biosynthetic capacity of roots from the uninfected parent species or variety. Cultures also released alkaloids from the roots into the growth medium. Such release was not however correlated with the ability of intact plants to mobilize alkaloids from the roots to aerial parts. The predictable nature of many aspects of secondary product synthesis in hairy roots should be advantageous to the development of biotechnological processes.

THE EFFECT OF GROWTH REGULATORS, LIGHT AND TEMPERATURE ON FLAVOUR PRODUCTION IN CELERY TISSUE CULTURES

SummaryCell suspensions of celery (Apium graveolens L.) were subcultured on media containing a range of auxins and antiauxins to replace 2,4‐dichlorophenoxyacetic acid (2,4‐D). Where the cultures showed a low growth rate and became green, the cells and media contained flavour compounds, the phthalides (3‐butyl phthalide and sedanenolide) and other terpenoid compounds. Maximum secondary product synthesis and greening was in media which contained 3,5‐dichlorophenoxy‐acetic acid (3,5‐D). In order to stimulate flavour synthesis in cultures in a medium containing 2,4‐D, the cultures were exposed to different fight and temperature regimes for varying periods during their growth cycle. Although growth was reduced in darkness and at high (30 °C) and intermediate (20 °C) temperatures, no stimulation of phthalide and terpenoid synthesis occurred. However, when the cultures were maintained at 4 °C for the first 5 d of the growth cycle and then transferred to 25 °C, phthalides and other terpenoids, particularly limonene, were released into the medium. An analysis of aggregated and finely dispersed cells on a 2,4‐D medium showed the aggregates contained phthalides and terpenoids, but these were not present in the dispersed cells. It is suggested that the altered internal cell environment in the green, aggregated or temperature stressed cells contributed to the ability of the cells to synthesize secondary products.