Chemical Defense Mechanisms Research Articles

Genome-wide analysis and expression profiling of the polyamine oxidase gene family in Solanum tuberosum L.

BackgroundPolyamine oxidase (PAO) is a crucial enzyme involved in the breakdown of polyamines (PAs) in plants. It not only regulates the levels of PAs, but also plays a role in the oxidative decomposition of PAs and the release of stress-related signals, contributing to the plant’s response and resistance to various adversities. While there have been numerous studies on the response of PAO to stress in other crops, there is a lack of research on this topic in potatoes, a major food crop.ResultsIn this study, we aimed to explore the biological function of the StPAO gene in potato growth and development, as well as its expression patterns under stress. Using bioinformatics methods, we identified 14 StPAO genes in the potato genome. Protein sequence comparisons revealed a high similarity between the PAO proteins of potato and Arabidopsis. Chromosomal mapping and gene structure analysis showed that the StPAO genes were not evenly distributed on the chromosome and all contained an amino-oxidase domain. Furthermore, analysis of the promoters of these genes revealed the presence of abiotic and stress-related cis-acting elements, indicating their potential role in responding to different stresses. To investigate the expression patterns of these genes under stress, we used qRT-PCR to study their response to high temperature, drought, and ABA stress. Our results showed that StPAO6 and StPAO10 were significantly up-regulated under high temperature stress, indicating that they were involved in the process of potato resistance to high temperatures. Similarly, StPAO1, StPAO3, and StPAO4 were significantly up-regulated under drought stress, indicating their potential role in potatoes’ responses to drought. After ABA treatment, the expression levels of StPAO4, StPAO5, StPAO7, and StPAO14 were significantly up-regulated, suggesting their involvement in chemical defense mechanisms. Interestingly, the expression of StPAO11–13 was inhibited by all three stresses.ConclusionsIn conclusion, our study highlights the multifunctional nature of the StPAO gene family in potatoes, which plays a crucial role in coping with various stresses. This research deepens our understanding of the potato StPAO gene family and provides a reference for future studies on its function. It also serves as a theoretical basis for breeding stress-resistant potato varieties in the future.

Bioelectronics for bitterness-based phytocompound detection using human bitter taste receptor nanodiscs

Various organisms produce several products to defend themselves from the environment and enemies. These natural products have pharmacological and biological activities and are used for therapeutic purposes, retaining bitter taste because of chemical defense mechanisms. Cnicin is a plant-derived bitter sesquiterpene lactone with pharmacological characteristics such as anti-bacterial, anti-myeloma, anti-cancer, anti-tumor, anti-oxidant, anti-inflammatory, allelopathic, and cytotoxic properties. Although many studies have focused on cnicin detection, they have limitations and novel cnicin-detecting strategies are required. In this study, we developed the bioelectronics for screening cnicin using its distinct taste. hTAS2R46 was produced using an Escherichia coli expression system and reconstituted into nanodiscs (NDs). The binding sites and energy between hTAS2R46 and cnicin were investigated using biosimulations. hTAS2R46–NDs were combined with a side-gated graphene micropatterned field-effect transistor (SGMFET) to construct hTAS2R46–NDs bioelectronics. The construction was examined by chemical and electrical characterization. The developed system exhibited unprecedented performance, 10 fM limit of detection, rapid response time (within 10 s), 0.1354 pM−1 equilibrium constant, and high selectivity. Furthermore, the system was stable as the sensing performance was maintained for 15 days. Therefore, the hTAS2R46-NDs bioelectronics can be utilized to screen cnicin from natural products and applied in the food and drug industries.

Nonenzymatic Sequestering of Formaldehyde into the Antibiotic Methylene-Bridged Dimer Phaeochromycin F by Streptomyces sp. OUCMDZ-4982 as a Possible Multipronged Chemical Defense Mechanism.

Metabolites with high chemical reactivity serve important roles in chemical defenses of organisms. Formaldehyde, as a simple and highly reactive small molecule, can be produced by microorganisms, plants, and animals. Its toxicity is well known, but information about its other biological functions remains scarce. Here, we report that the natural product SEK34b produced by Streptomyces species can react nonenzymatically with formaldehyde in water to yield the methylene-bridged dimer phaeochromycin F. This process can eliminate the toxic substance formaldehyde produced by Staphylococcus aureus. Furthermore, there is a substantial inhibitory impact of phaeochromycin F on S. aureus. We hypothesize that these constitute an integrated system of defense and attack of Streptomyces species against competitors. Our study indicates that formaldehyde can react with vancomycin and tigecycline under mild conditions to generate the derivatives bearing an imidazolidin-4-one moiety, thereby reducing the antibacterial activity of these antibiotics. These data provide a possible chemical interaction mechanism of bacteria involving the nonenzymatic reactions of formaldehyde with highly reactive natural products.

An extensive review of mutualistic and similar ecological associations involving tarantulas (Araneae: Theraphosidae), with a new hypothesis on the evolution of their hirsuteness

ABSTRACT Mutualistic and similar ecological associations between tarantulas (Mygalomorphae: Theraphosidae) and other animals are reviewed. Such associations are found to occur in at least nine theraphosid subfamilies. We present 63 new cases of theraphosid–anuran associations from 10 countries, documenting these interactions for the first time in Brazil, Chile, the Dominican Republic, and the Philippines. These findings are the first documentation of such associations for 13 theraphosid and 20 anuran taxa. Additionally, we report, for the first time, associations potentially of mutualistic nature between tarantulas and snakes, whip spiders, and harvestmen. Furthermore, we provide new reports of associations with ants and termites. While some of these interactions appear to be merely tolerated cohabitations, those involving anurans and ants seem to be more prevalent and complex, clearly offering benefits for both organisms. Additionally, based on multiple observations and field experiments, we propose a new hypothesis regarding the evolution of hirsuteness in theraphosids as a defensive strategy against predatory ants. This hypothesis supports previous findings that suggest a similar function for urticating setae incorporated into egg sacs and moulting mats. We further document a unique escape strategy against ants in New World arboreal theraphosids. Finally, the possibility of a chemical defence mechanism through specialised epidermal glands in theraphosids is briefly discussed.

Leaf Endophytes Relationship with Host Metabolome Expression in Tropical Gymnosperms.

Plant-microbe interactions play a pivotal role in shaping host fitness, especially concerning chemical defense mechanisms. In cycads, establishing direct correlations between specific endophytic microbes and the synthesis of highly toxic defensive phytochemicals has been challenging. Our research delves into the intricate relationship between plant-microbe associations and the variation of secondary metabolite production in two closely related Zamia species that grow in distinct habitats; terrestrial and epiphytic. Employing an integrated approach, we combined microbial metabarcoding, which characterize the leaf endophytic bacterial and fungal communities, with untargeted metabolomics to test if the relative abundances of specific microbial taxa in these two Zamia species were associated with different metabolome profiles. The two species studied shared approximately 90% of the metabolites spanning diverse biosynthetic pathways: alkaloids, amino acids, carbohydrates, fatty acids, polyketides, shikimates, phenylpropanoids, and terpenoids. Co-occurrence networks revealed positive associations among metabolites from different pathways, underscoring the complexity of their interactions. Our integrated analysis demonstrated to some degree that the intraspecific variation in metabolome profiles of the two host species was associated with the abundance of bacterial orders Acidobacteriales and Frankiales, as well as the fungal endophytes belonging to the orders Chaetothyriales, Glomerellales, Heliotiales, Hypocreales, and Sordariales. We further associate individual metabolic similarity with four specific fungal endophyte members of the core microbiota, but no specific bacterial taxa associations were identified. This study represents a pioneering investigation to characterize leaf endophytes and their association with metabolomes in tropical gymnosperms, laying the groundwork for deeper inquiries into this complex domain.

Sea Cucumber Viscera Contains Novel Non-Holostane-Type Glycoside Toxins that Possess a Putative Chemical Defense Function.

Sea cucumbers frequently expel their guts in response to predators and an aversive environment, a behavior perceived as releasing repellents involved in chemical defense mechanisms. To investigate the chemical nature of the repellent, the viscera of stressed sea cucumbers (Apostichopus japonicus) in the Yellow Sea of China were collected and chemically analyzed. Two novel non-holostane triterpene glycosides were isolated, and the chemical structures were elucidated as 3ꞵ-O-[ꞵ-D-glucopyranosyl-(1→2)-ꞵ-D-xylopyranosyl]-(20S)-hydroxylanosta-7,25-diene-18(16)-lactone (1) and 3ꞵ-O-[ꞵ-D-quinovopyranosyl-(1→2)-ꞵ-D-xylopyranosyl]-(20S)-hydroxylanosta-7,25-diene-18(16)-lactone (2) by spectroscopic and mass-spectrometric analyses, exemplifying a triterpene glycoside constituent of an oligosaccharide containing two sugar-units and a non-holostane aglycone. Zebrafish embryos were exposed to various doses of 1 and 2 from 4 to 96 hpf. Compound 1 exposure showed 96h-LC50 41.5 µM and an increased zebrafish mortality rates in roughly in a dose- and time-dependent manner. Compound 2, with different sugar substitution, exhibited no mortality and moderate teratogenic toxicity with a 96h-EC50 of 173.5 µM. Zebrafish embryos exhibited teratogenic effects, such as reduced hatchability and total body length. The study found that triterpene saponin from A. japonicus viscera had acute toxicity in zebrafish embryos, indicating a potential chemical defense role in the marine ecosystem.

Bruchid Infestation Was Associated With Agronomic Traits in Field-grown Faba Bean Genotypes

Bruchus rufimanus, a univoltine seed weevil (bruchid), can cause severe seed yield and quality losses in faba beans restricting crop profitability and expansion. Chemical insecticide applications have been reported of low effectiveness and thus, growing genotypes tolerant to bruchid has been suggested as an alternative. Ten faba bean (Viciafaba L.) accessions belonging to three varieties (var. major (seven accessions), var. minor (two accessions), var. equina (one accession)) were tested under field conditions for two growing seasons. Agronomic and seed traits were determined in an attempt to associate any tolerance to bruchid with easily-assessible, highly-heritable characters in order to be used as indirect selection criteria. The genotypes varied in bruchid tolerance (percentage of bruchid emergence holes (BD), percentage of endoparasitoid (Triaspis thoracica) emergence holes and bruchid infestation level (BI = BD + PD)), agronomic traits and seed properties. The dark-colored, small- and medium-seeded accessions (var. minor and var. equina), commonly used for feed, had the lowest BI (4.21–8.17%) ranging below the limit of 10% set as the highest acceptable for using faba beans as feed. Large-seeded accessions (var. major), which had light-colored seed coat (testa) with yellow hue, showed BI from 11.80% up to 24.54%, far-above the limit of 3% for seeds used as food. Apart from the seed size and color, susceptible genotypes had more seeds per pod, less pods and less branches per plant, possibly offering an easy access to females for laying more eggs on the limited number of pods, albeit the more space and food (higher protein content per seed) they offer to the developing larvae. Phenols and tannins in seeds, a putative chemical defense mechanism against bruchid, did not associate with the percentage of bruchid- or endoparasitoid-damaged seeds. Concluding, certain plant architectural traits and seed properties related to bruchid infestation in faba beans can be used as useful tools to select tolerant genotypes.

Genetic background of juniper (Juniperus spp.) consumption predicted by fecal near-infrared spectroscopy in divergently selected goats raised in harsh rangeland environments

BackgroundJunipers (Juniperus spp.) are woody native, invasive plants that have caused encroachment problems in the U.S. western rangelands, decreasing forage productivity and biodiversity. A potential solution to this issue is using goats in targeted grazing programs. However, junipers, which grow in dry and harsh environmental conditions, use chemical defense mechanisms to deter herbivores. Therefore, genetically selecting goats for increased juniper consumption is of great interest for regenerative rangeland management. In this context, the primary objectives of this study were to: 1) estimate variance components and genetic parameters for predicted juniper consumption in divergently selected Angora (ANG) and composite Boer x Spanish (BS) goat populations grazing on Western U.S. rangelands; and 2) to identify genomic regions, candidate genes, and biological pathways associated with juniper consumption in these goat populations.ResultsThe average juniper consumption was 22.4% (± 18.7%) and 7.01% (± 12.1%) in the BS and ANG populations, respectively. The heritability estimates (realized heritability within parenthesis) for juniper consumption were 0.43 ± 0.02 (0.34 ± 0.06) and 0.19 ± 0.03 (0.13 ± 0.03) in BS and ANG, respectively, indicating that juniper consumption can be increased through genetic selection. The repeatability values of predicted juniper consumption were 0.45 for BS and 0.28 for ANG. A total of 571 significant SNP located within or close to 231 genes in BS, and 116 SNP related to 183 genes in ANG were identified based on the genome-wide association analyses. These genes are primarily associated with biological pathways and gene ontology terms related to olfactory receptors, intestinal absorption, and immunity response.ConclusionsThese findings suggest that juniper consumption is a heritable trait of polygenic inheritance influenced by multiple genes of small effects. The genetic parameters calculated indicate that juniper consumption can be genetically improved in both goat populations.

Norsesquiterpenes from the Latex of Euphorbia dentata and Their Chemical Defense Mechanisms against Helicoverpa armigera.

Euphorbia dentata (Euphorbiaceae), an invasive weed, is rarely eaten by herbivorous insects and could secrete a large amount of white latex, causing a serious threat to local natural vegetation, agricultural production and human health. In order to prevent this plant from causing more negative effects on humans, it is necessary to understand and utilize the chemical relationships between the latex of E. dentata and herbivorous insects. In this study, three new norsesquiterpenes (1-3), together with seven known analogues (4-10), were isolated and identified from the latex of E. dentata. All norsesquiterpenes (1-10) showed antifeedant and growth-inhibitory effects on H. armigera with varying levels, especially compounds 1 and 2. In addition, the action mechanisms of active compounds (1-3) were revealed by detoxifying enzyme (AchE, CarE, GST and MFO) activities and corresponding molecular docking analyses. Our findings provide a new idea for the development and utilization of the latex of E. dentata, as well as a potential application of norsesquiterpenes in botanical insecticides.

Identification and Localization of Labile Molecules in Broccoli Cell by CLA-ICP-MS and Single-Cell Nanospray HRMS.

Although molecular analysis and imaging by mass spectrometry are emerging as tools to identify metabolites and determine their distribution in cells and tissues, it is difficult to directly analyze the labile molecules at the single-cell level. Glucosinolate (GL) is a plant-active substance with much attention as a chemical defense mechanism known as a "mustard oil bomb" in broccoli. When tissue is damaged, these substances undergo rapid degradation, making them unsuitable for conventional mass spectrometry (MS), particularly for surface MS imaging analysis methods that necessitate intricate preprocessing. Herein, a strategy combining cryogenic laser ablation inductively coupled mass spectrometry (CLA-ICP-MS) and capillary microsampling nanospray high-resolution mass spectrometry (HRMS) was developed. The sulfur-rich microzone in tissue which was thought as a suspect GL-rich cell population was located via CLA-ICP-MS. Three GLs in single cells were accurately identified by nanospray HRMS with a hydrogen/deuterium exchange reaction. Subsequently, cell-by-cell imaging by nanospray HRMS showed that the GL-rich cells were below the stalk surface by approximately 30 μm. This proposed strategy can also be applied to rapidly identify labile compounds and localize molecule-rich cells in tissues.

Genome-Wide Analysis and Expression Profiling of the Glutathione Peroxidase-like Enzyme Gene Family in Solanum tuberosum.

Glutathione peroxidase-like enzyme is an important enzymatic antioxidant in plants. It is involved in scavenging reactive oxygen species, which can effectively prevent oxidative damage and improve resistance. GPXL has been studied in many plants but has not been reported in potatoes, the world's fourth-largest food crop. This study identified eight StGPXL genes in potatoes for the first time through genome-wide bioinformatics analysis and further studied the expression patterns of these genes using qRT-PCR. The results showed that the expression of StGPXL1 was significantly upregulated under high-temperature stress, indicating its involvement in potato defense against high-temperature stress, while the expression levels of StGPXL4 and StGPXL5 were significantly downregulated. The expression of StGPXL1, StGPXL2, StGPXL3, and StGPXL6 was significantly upregulated under drought stress, indicating their involvement in potato defense against drought stress. After MeJA hormone treatment, the expression level of StGPXL6 was significantly upregulated, indicating its involvement in the chemical defense mechanism of potatoes. The expression of all StGPXL genes is inhibited under biotic stress, which indicates that GPXL is a multifunctional gene family, which may endow plants with resistance to various stresses. This study will help deepen the understanding of the function of the potato GPXL gene family, provide comprehensive information for the further analysis of the molecular function of the potato GPXL gene family as well as a theoretical basis for potato molecular breeding.

Ontogenetic change in effectiveness of chemical defence against different predators in Oxycarenus true bugs.

Many prey species change their antipredator defence during ontogeny, which may be connected to different potential predators over the life cycle of the prey. To test this hypothesis, we compared reactions of two predator taxa - spiders and birds - to larvae and adults of two invasive true bug species, Oxycarenus hyalinipennis and Oxycarenus lavaterae (Heteroptera: Oxycarenidae) with life-stage-specific chemical defence mechanisms. The reactions to larvae and adults of both true bug species strikingly differed between the two predator taxa. The spiders were deterred by the defences of adult bugs, but the larval defences were ineffective against them. By contrast, birds attacked the larvae considerably less often than the adult bugs. The results indicate a predator-specific ontogenetic change in defence effectiveness of both Oxycarenus species. The change in defence is likely linked to the life-stage-specific composition of secretions in both species: whereas secretions of larvae are dominated by unsaturated aldehydes, secretions of adults are rich in terpenoids, which probably serve dual function of defensive chemicals and pheromones. Our results highlight the variation in defence between different life stages and the importance of testing responses of different types of predators.

Newly-sprouted leaves at the stem base differ anatomically and histochemically from the ‎crown leaves in Ficus johannis

ABSTRACT Ficus species evolved physical and chemical defense mechanisms to cope with variable environmental conditions. Field observation of Ficus johannis Boiss. (Mountain Fig) indicated that newly-sprouted leaves developed at the base of the plant are skin irritating, but the crown leaves, out of animal reach, do not. Here, we investigated the anatomical and phytochemical characteristics of both leaves of F. johannis growing in the arid mountains of the United Arab Emirates (UAE). The results showed the presence of numerous tapering non-glandular and a few glandular trichomes on the newly-sprouted leaves. Gas chromatography-mass spectrometry (GC-MS) analysis showed the presence of 107 metabolites; out of them, 16 compounds were identified in the newly-sprouted leaves but not in the crown ones. β-Amyrin, α- amyrin, and β-amyrin acetate, known as irritant chemicals, were~5, 3, and 200 times higher in the newly-sprouted leaves than in the crown leaves, respectively. Our study is the first to report the presence of stinging trichomes in Ficus species, a rare type that has been reported in a few angiosperm families. These results indicated that the variety of trichomes on the newly-sprouted leaves and the leaf’s unique metabolites provide sufficient protection mechanisms against grazing animals.

Aloe barbadensis rinds employ physical and chemical defense mechanisms against insect herbivores with varying success

Plants deter herbivory through a suite of physical and chemical defenses. While most studies have focused on understanding one or the other, efficient plant defense against herbivory is often cumulative. To examine this, we used Aloe barbadensis (Asphodelaceae) as a model, since in natural settings, the species is found to be well-defended against insect herbivores. To start with, we hypothesized that the epicuticular wax potentially plays an important role in herbivore defense as the major physical defense. To test our hypothesis, we conducted bioactivity-guided extraction and polarity-based fractionation of A. barbadensis rinds. We then mixed them into an artificial diet, to determine the effect of these compounds on the growth and development of two species of caterpillars, tobacco hornworm (Manduca sexta; Lepidoptera: Sphingidae) and fall armyworm (Spodoptera frugiperda; Lepidoptera: Noctuidae). Thereafter, we identified and quantified different volatile compounds emitted by the epicuticular waxes to analyze if any herbivore deterrent compounds are emitted and might be responsible for A. barbadensis repelling insect herbivores. Our results show that the surface waxes and volatiles prevented the feeding of the larvae, and the extracts from the rinds differentially affected their growth and development. Our results do not definitively explain the entire defense phenotype; however, they do help to shed light on the combination of physical and chemical mechanisms enacted by the species.

Growth Responses of the Perennial Grass, Phalaris Aquatica L., to Cutting Frequency and Influence on Secondary Metabolites and Antioxidant Activity

Highlights Defoliation initiates physiological recovery and chemical defense mechanisms in Phalaris aquatica. Under infrequent defoliation treatment, P. aquatica has high DM production. Defoliation severity on herbage regrowth was associated with variation of secondary metabolite content and antioxidant activity. Phalaris may be suited to conservation pasture systems; the interval between cuts is about six weeks to maximize rates of regrowth. Results indicate that Phalaris may be used as fodder crop to sustained production and food security. Abstract. Perennial grasses are the key to the economic and environmental sustainability of pastures for livestock, and in arid and semi-arid environments, they can provide multiple ecosystem services more effectively than production systems based on annual crops. The objective of this study was to evaluate the effect of different defoliation frequencies on forage production and nutritive value of the Phalaris aquatica L. variety Soukra under field conditions in Tunis, Tunisia, over a period of 12 weeks. We tested four defoliation frequencies: (1) severe, (2) moderate, (3) infrequent, and (4) control. The growth responses measured were plant tiller number (NT), dry matter production (DM), and relative leaf regrowth rate (RLR). DM under the severe and moderate defoliation frequencies was 7% and 41% less than under control defoliation, respectively. However, DM production under infrequent defoliation was 91% and 43% higher than under severe and moderate defoliation. The relative leaf regrowth rate was affected by defoliation frequency; the highest regrowth rate was under severe treatment. However, tillering of P. aquatica was reduced under the severe and moderate frequencies of defoliation. Under increased defoliation frequencies, concentrations of secondary metabolites significantly decreased; total polyphenol content, flavonoid content, and tannin contents were higher in control and infrequent than in moderate and severe treatments. Antioxidant activity also decreased significantly with defoliation compared to the control treatment. There were no significant differences (P > 0.05) in ABTS (3-ethylbenzothiazoline-6-sulfonic acid) among the defoliation frequencies. Pearson's r correlation and PCA (Principal component analysis) data revealed that growth parameters, secondary metabolites, and antioxidant activity have positive and negative correlations in distinguishing the control and defoliation treatments. Results indicate that P. aquatica management should target moderate harvest rates in the adoption of perennial grass forage production systems in Tunisia. Use of perennial grasses for forage production can contribute to sustained production, food security, and rural livelihoods, and move farming systems towards providing multiple economic, environmental, and social benefits. Keywords: ABTS, Defoliation frequency, DPPH, Flavonoids, Growth responses, Matter production, Perennial grasses, Phalaris, Polyphenols.

Assessing the effect of antimony pressure on trypanothione reductase activity in Leishmania (Viannia) braziliensis

Leishmania parasites have an oxidative and chemical defense mechanism called trypanothione system (T[SH]2), the most abundant thiol system in trypanosomatids. This system has a central role in processing pentavalent antimony and resistance has been related to a better capacity to metabolize it through the activation of T[SH]2 enzymatic cascade. A biochemical approach was applied to assess the effect of trivalent (SbIII) and pentavalent antimony (SbV) on Trypanothione Reductase (TR) activity of two Leishmania (Viannia) braziliensis clinical isolates, which were labeled as responder (R) and non-responder (NR) after patient treatment with Glucantime®. Both isolates were characterized based on in vitro susceptibility to SbIII and SbV and trypanothione reductase (TR) activity. SbIII and SbV discriminated susceptibility profiles in all parasite forms, since isolate NR had significantly higher EC50 values than isolate R. Differences were observed in TR activity between promastigotes, axenic amastigotes and intracellular amastigotes: R (0.439 ± 0.009, 0.103 ± 0.01 and 0.185 ± 0.01AU.min−1.μg of protein−1) and NR (1.083 ± 0.04, 0.914 ± 0.04 and 0.343 ± 0.04 AU. min−1.μg of protein−1), respectively. Incubation with SbIII and SbV using each form EC50 value caused a time-dependent differential effect on TR activity suggesting that oxidative defense is related to the antimony susceptibility phenotype. Data gathered here shows a biochemical approach able to discriminate two L. (V.) braziliensis clinical isolates measurements TR activity of promastigotes, axenic amastigotes and intracellular amastigotes.

Enhancing Bioproducts in Seaweeds via Sustainable Aquaculture: Antioxidant and Sun-Protection Compounds.

Marine macroalgae are considered an untapped source of healthy natural metabolites and their market demand is rapidly increasing. Intertidal macroalgae present chemical defense mechanisms that enable them to thrive under changing environmental conditions. These intracellular chemicals include compounds that can be used for human benefit. The aim of this study was to test cultivation protocols that direct seaweed metabolic responses to enhance the production of target antioxidant and photoprotective biomaterials. We present an original integrated multi-trophic aquaculture (IMTA) design, based on a two-phase cultivation plan, in which three seaweed species were initially fed by fish effluents, and subsequently exposed to various abiotic stresses, namely, high irradiance, nutrient starvation, and high salinity. The combined effect of the IMTA's high nutrient concentrations and/or followed by the abiotic stressors enhanced the seaweeds' content of mycosporine-like amino acids (MAAs) by 2.3-fold, phenolic compounds by 1.4-fold, and their antioxidant capacity by 1.8-fold. The Sun Protection Factor (SPF) rose by 2.7-fold, and the chlorophyll and phycobiliprotein synthesis was stimulated dramatically by an order of magnitude. Our integrated cultivation system design offers a sustainable approach, with the potential to be adopted by emerging industries for food and health applications.

Influence of tannic acid concentration on the physicochemical characteristics of saliva of spider monkeys (Ateles geoffroyi).

Tannins are a chemical defense mechanism of plants consumed by herbivores. Variations in salivary physicochemical characteristics such as pH, total protein concentration (TP), and presence of proline-rich proteins (PRPs) in animals have been reported as a mechanism to protect the oral cavity when consuming food with variations in pH and tannins. Variations in salivary physiochemistry as adaptations for consuming tannin-rich foods have been found in omnivorous and folivorous primates, but have not yet been reported in frugivorous species such as spider monkeys. We therefore assessed changes in pH using test strips, TP concentration by measuring absorbance at 595 nm in a spectrophotometer and salivary PRPs using the SDS-PAGE electrophoresis technique in the saliva of nine captive spider monkeys in response to the consumption of solutions with different concentrations of tannic acid. The results showed variations in pH, TP concentration and the presence and variation of possible salivary PRPs associated with tannic acid concentration. These findings suggest that spider monkeys may tailor their salivary physicochemical characteristics in response to the ingestion of potentially toxic compounds.

Alciporin, a pore-forming protein as complementary defense mechanism in Millepora alcicornis

Millepora alcicornis (Cnidaria: Hydrozoa), known as fire coral, is a tropical species settled in marine ecosystems of the Canary Islands in the last years. This hydrocoral biosynthesizes toxins involved in chemical defense and prey capture mechanisms. Toxicological studies have shown that the venom contained in the nematocysts of Millepora species is mainly composed of thermolabile proteins that display hemolytic activity, causing skin irritation and burn-like lesions upon contact. As a continuation of a previous study, the chromatographic fractionation of the aqueous extracts of M. alcicornis has confirmed the coexistence of proteins of different nature responsible for the hemolytic effects of red blood cells (RBCs) through two different mechanisms. Aside from the already described phospholipase A2 (PLA2) activity, in this work the presence of alciporin, a pore-forming protein (PFP), has been established for the first time for M. alcicornis. The sequence analysis revealed that alciporin fit an actinoporin with high homology to stichotoxins. The hemolytic effects of alciporin were analyzed and sphingomyelin was identified as its biological target. Also, the evolution of the hemolytic damage produced at the nanoscale has been studied using atomic force microscopy (AFM).

Insect Gut Isolate Pseudomonas sp. Strain Nvir Degrades the Toxic Plant Metabolite Nitropropionic Acid.

ABSTRACTNitropropionic acid (NPA) is a widely distributed naturally occurring nitroaliphatic toxin produced by leguminous plants and fungi. The Southern green shield bug feeds on leguminous plants and shows no symptoms of intoxication. Likewise, its gut-associated microorganisms are subjected to high levels of this toxic compound. In this study, we isolated a bacterium from this insect's gut system, classified as Pseudomonas sp. strain Nvir, that was highly resistant to NPA and was fully degrading it to inorganic nitrogen compounds and carbon dioxide. In order to understand the metabolic fate of NPA, we traced the fate of all atoms of the NPA molecule using isotope tracing experiments with [15N]NPA and [1-13C]NPA, in addition to experiments with uniformly 13C-labeled biomass that was used to follow the incorporation of 12C atoms from [U-12C]NPA into tricarboxylic acid cycle intermediates. With the help of genomics and transcriptomics, we uncovered the isolate’s NPA degradation pathway, which involves a putative propionate-3-nitronate monooxygenase responsible for the first step of NPA degradation. The discovered protein shares only 32% sequence identity with previously described propionate-3-nitronate monooxygenases. Finally, we advocate that NPA-degrading bacteria might find application in biotechnology, and their unique enzymes might be used in biosynthesis, bioremediation, and in dealing with postharvest NPA contamination in economically important products.IMPORTANCE Plants have evolved sophisticated chemical defense mechanisms, such as the production of plant toxins in order to deter herbivores. One example of such a plant toxin is nitropropionic acid (NPA), which is produced by leguminous plants and also by certain fungi. In this project, we have isolated a bacterium from the intestinal tract of a pest insect, the Southern green shield bug, that is able to degrade NPA. Through a multiomics approach, we identified the respective metabolic pathway and determined the metabolic fate of all atoms of the NPA molecule. In addition, we provide a new genetic marker that can be used for genome mining toward NPA degradation. The discovery of degradation pathways of plant toxins by environmental bacteria opens new possibilities for pretreatment of contaminated food and feed sources and characterization of understudied enzymes allows their broad application in biotechnology.