Global metabolic changes induced by arbuscular mycorrhizal fungi in oregano plants grown under ambient and elevated levels of atmospheric CO2

The potential of Actinoplanes spp. for alleviating the oxidative stress induced by thallium toxicity in wheat plants

To reduce heavy metal toxicity, like that induced by thallium (TI) in plants, growth-promoting bacteria (GPB) are a widely used to enhance plant tolerance to heavy metals toxicity. In our study, we characterized seven GPB and identified Actinoplanes spp., as the most active strain. This bioactive strain was then applied to alleviate TI phytotoxicity. TI contamination (20 mg/kg soil) induced TI bioaccumulation, reducing wheat growth (biomass accumulation) and photosynthesis rate, by about 55% and 90%, respectively. TI stress also induced oxidative damages as indicated by increased oxidative markers (H2O2 and lipid peroxidation (MDA)). Interestingly, Actinoplanes spp. significantly reduced growth inhibition and oxidative stress by 20% and 70%, respectively. As a defense mechanism to mitigate the TI toxicity, wheat plants showed improved antioxidant and detoxification defense including increased phenolic and tocopherols levels as well as peroxidase (POX), catalase (CAT), superoxide dismutase (SOD), and glutathione reductase (GR) enzymes activities. These defense mechanisms were further induced by Actinoplanes spp. Additionally, Actinoplanes spp. increased the production of heavy metal-binding ligands such as metallothionein, phytochelatins, total glutathione, and glutathione S-transferase activity by 100%, 90%, 120%, and 100%, respectively. This study, therefore, elucidated the physiological and biochemical bases underlying TI-stress mitigation impact of Actinoplanes spp. Overall, Actinoplanes spp. holds promise as a valuable approach for ameliorating TI toxicity in plants. KEYBOARD: Actinobacteria, Bioaccumulation, Detoxification, Membrane damage, Redox regulation.

Study on Differences of Metabolites among Different Ganoderma Species with Comprehensive Metabolomics

In traditional Chinese medicine, Ganoderma is a kind of edible and medicinal mushroom, which is widely used because of its significant pharmacological activity. There are many species within the Ganoderma genus, each with different material bases and applications. However, detailed studies on these species are still lacking. In this study, we investigated the metabolites of G. leacontextum (B), G. lucidum (C), G. tsugae (S) from Changbai Mountain, and G. tsugae (M) from Mongolia using metabolomics. The PCA results indicated minimal differences between M and S, whereas B and S exhibited significant variations. A total of 708 differential metabolites were identified in this study, with steroids, triterpenoids, phenols, and quinones being the major metabolites. Specifically, triterpenoids and steroids were higher in C. Meanwhile, phenolic compounds were more abundant in B. Additionally, quinones were more abundant in M and S. We validated some of the main compounds, and the results showed that paracetamol was most abundant in B, making paracetamol a potential marker for identifying B. Additionally, vitamin K3 was found to be more abundant in M and S, which can serve as a marker for their identification. This study provides new insights and a theoretical basis for the development and utilization of the genus Ganoderma.

Mycorrhizal Symbiosis Can Change the Composition of Secondary Metabolites in Fruits of Solanum nigrum L

Solanum nigrum is a common weed in arable land, while being used in traditional medicine around the world due to its remarkable levels of valuable secondary metabolites. Agronomic and biological techniques can alter the production of a specific metabolite by influencing plant growth and metabolism. The effects of colonization with three arbuscular mycorrhizal fungi (AMF), including Funneliformis mosseae, Rhizoglomus intraradices, and Rhizoglomus fasciculatum, on the chemical composition of S. nigrum fruits were evaluated by gas chromatography-mass spectrometry (GC-MS) analysis. More than 100 different chemical constituents were evaluated by GC-MS. Our study revealed that the levels of phenols (quinic acid), benzenes (hydroquinone), sulfur-containing compounds, lactone and carboxylic acids were improved by R. intraradices. In contrast, hydroxymethylfurfural increased by 68 % in R. fasciculatum inoculated with uninoculated S. nigrum plants, and this species was also the most efficient in inducing sugar compounds (D-galactose, lactose, and melezitose). Our results suggest that AMF colonization is an effective biological strategy that can alter the chemical composition and improve the medicinal properties of S. nigrum.

Diversity, Distribution, and applications of arbuscular mycorrhizal fungi in the Arabian Peninsula

Investigations of arbuscular mycorrhizal fungi (AMF) received extreme interests among scientist including agronomists and environmental scientists. This interest is linked to advantages provided by AMF in enhancing the nutrients of their hosts via improving photosynthetic pigments and antioxidant production. Further, it also positively alters the production of plant hormones. AMF through its associations with plants obtain carbon while in exchange, provide nutrients. AMF have been reported to improve the growth of Tageteserecta, Zea mays, Panicum turgidum, Arachis hypogaea, Triticum aestivum and others. This review further documented the occurrence, diversity, distribution, and agricultural applications of AMF species reported in the Arabian Peninsula. Overall, we documented 20 genera and 61 species of Glomeromycota in the Arabian Peninsula representing 46.51 % of genera and 17.88 % of species of AMF known so far. Funneliformis mosseae has found to be the most widely distributed species followed by Claroideoglomus etuicatum. There are 35 research articles focused on Arabian Peninsula where the stress conditions like drought, salinity and pollutants are prevailed. Only one group studied the influence of AMF on disease resistance, while salinity, drought, and cadmium stresses were investigated in 18, 6, and 4 investigations, respectively. The genus Glomus was the focus of most studies. The conducted research in the Arabian Peninsula is not enough to understand AMF taxonomy and their functional role in plant growth. Expanding the scope of detection of AMF, especially in coastal areas is essential. Future studies on biodiversity of AMF are essential.

Chitosan nanoparticles upregulate C and N metabolism in soybean plants grown under elevated levels of atmospheric carbon dioxide

Despite the wide utilization of chitosan nanoparticles (CSNPs) as a promising approach for sustainable agriculture, their efficiency under elevated CO2 (eCO2), has not been evaluated. The interactive effects of CSNPs and eCO2 were evaluated on the growth and C and N metabolism of soybean plants. Plants were treated with CSNPs and grown under ambient CO2 (410 ppm, aCO2) or eCO2 (645 ppm). Regardless of CO2 level, CSNPs improved the net photosynthetic rate. CSNPs aggravated the effect of eCO2 treatment on the levels of non-structural carbohydrates (i.e., glucose, fructose, sucrose, and starch), especially in shoots, which was inconsistence with the upregulation of carbohydrates metabolizing enzymes. Being the most pivotal energetic and signaling organic compounds in higher plants, the synergistic action of CSNPs and eCO2 on the accumulation of soluble sugars upregulated the N metabolism as indicated by induced activities of nitrate reductase, arginase, glutamate dehydrogenase, glutamine synthetase, and glutamine oxoglutarate aminotransferase which was manifested finally as increased shoot and root total nitrogen content as well as proline and aspartate in roots. At the hormonal level, the coexistence of eCO2 with CSNPs further supports their positive impact on the contents of IAA and, to a lesser extent, GAs. The present data prove that the biofertilization capacity of CSNPs is even more potent under futuristic eCO2 levels and could even further improve the growth and resilience of plants.

Metabolome profiling of arbuscular mycorrhizal fungus treated Ocimum tenuiflorum L. provides insights into deviation in allocation of carbon compounds to secondary metabolism

Arbuscular mycorrhiza (AM) has been reported to influence secondary metabolism of Ocimum tenuiflorum L., thereby improving its therapeutic and commercial importance. To explain changes in the secondary metabolite profile, the study reports effects of AM on leaf metabolome of two high yielding genotypes of O. tenuiflorum inoculated with Rhizophagus intraradices. NMR-based non-targeted metabolic fingerprinting was related to changes at physiological, biochemical, and molecular levels in mycorrhizal (M) plants. AM resulted in higher accumulation of sucrose, which could be related with enhanced photosynthesis by virtue of increased uptake of mineral nutrients. A strong positive correlation between sucrose and net photosynthetic rate and sucrose and mineral nutrients supported that AM-mediated increase in uptake of mineral nutrients is associated with enhanced photosynthetic rate and accumulation of sucrose. Further, higher sucrose synthase activity resulted in increased glucose. Hexokinase activity was also higher in M plants resulting in higher pyruvate accumulation. On the contrary, Krebs cycle was compromised in M plants as evident by lower activities of its enzymes and concentrations of organic and amino acids. Nevertheless, AM increased activities and expressions of enzymes of terpenoid biosynthesis, shikimate, and phenylpropanoid pathways, thereby resulting in augmented production of terpenoids, phenylalanine, and phenols, respectively. Thus, metabolic reprogramming downstream of glycolysis was apparent wherein AMF resulted in more allocation of carbon resources to secondary metabolism as opposed to primary metabolism, which was supported by Pearson's correlation analysis. Higher C:N ratio in M plants explains the provision of more carbon resources to secondary metabolism as against primary metabolism.

Arbuscular mycorrhizal fungi as an effective approach to enhance the growth and metabolism of soybean plants under thallium (TI) toxicity

Thallium (TI) is a toxic metal that can trigger harmful impacts on growth and metabolism of plants. Utilizing arbuscular mycorrhizal fungi (AMF) proves to be an effective strategy for alleviating heavy metal toxicity in plants. To this end, AMF were applied to mitigate TI toxic effects on the growth, primary and secondary metabolism of soybean plants. Here, TI stress inhibited the growth and photosynthetic parameters of soybean plants. It also increased the oxidative damage as demonstrated by increased levels of oxidative markers, (MDA and lipoxygenase (LOX) activity). However, AMF could mitigate the reduction in growth and photosynthesis induced by TI, as well as the induction of oxidative damage. To overcome TI toxicity, AMF increased the levels and metabolism of osmolytes such as proline in soybean plants. This was in line with the increased activities of key enzymes that involved in proline biosynthesis (e.g., P5CS (pyrroline-5-carboxylate synthetase), P5CR (pyrroline-5-carboxylate reductase) and OAT (ornithine aminotransferase) under the AMF and/or TI treatments. Furthermore, soybean plants could benefit from the synergism between AMF and TI to enhance the contents of individual (e.g., spermine and spermidine) and total polyamines as well as their metabolic enzymes (e.g., arginine decarboxylase and ornithine decarboxylase). Overall, the combined application of AMF emerges as a viable approach for alleviating TI toxicity in soybean plants.

Adaptive response of flavonoids in Robinia pseudoacacia L. affected by the contamination of cadmium and elevated CO2 to arbuscular mycorrhizal symbiosis

As a key component in non-enzyme resistance system, flavonoids play a crucial role in the plant growth and defenses, which are significantly affected by biotic and abiotic factors such as fungi, bacteria, viruses, heavy metals, and atmospheric CO2. Arbuscular mycorrhizal fungi (AMF) play an important role in enhancing plant tolerance to adverse environments, which can significantly affect the synthesis of flavonoids by forming mycorrhizal symbionts with plant roots. However, few studies explored the combined effects of AMF, elevated CO2, and heavy metals on flavonoids in plants. Here, we investigated the adaptive response of flavonoids accumulation in Robinia pseudoacacia L. seedlings affected by the contamination of cadmium (Cd) and elevated CO2 to arbuscular mycorrhizal symbiosis. The results showed that G. mosseae decreased (p < 0.05) Cd content in leaves by 62.2% under elevated CO2. Moreover, G. mosseae colonization led to significant decreases in robinin, quercetin, kaempferol and acacetin by 17.4%, 11.1%, 15.5% and 23.1% under elevated CO2 + Cd, respectively. Additionally, G. mosseae down-regulated (p < 0.05) expression levels of phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS) genes under elevated CO2 + Cd, and CHS and uridine diphosphate flavonoid glucosyltransferase (UFGT) activities decreased (p < 0.05). Quercetin, kaempferol and acacetin showed positive (p < 0.05) correlation with PAL and CHS genes expression and PAL, CHS, and UFGT activities. Cadmium, C/N ratio, carotenoids, leaf biomass, total chlorophyll, P, and starch in leaves and G. mosseae colonization rate in roots influenced (p < 0.05) flavonoids content. Overall, G. mosseae reduced flavonoids synthesis by down-regulating gene expression levels and activities of key enzymes under elevated CO2 + Cd. The results improved our understanding of the regulation of AMF on non-enzymatic resistance of plants grown in heavy metal-contaminated soils under increasing atmospheric CO2 scenarios.

The Application of Arbuscular Mycorrhizal Fungi as Microbial Biostimulant, Sustainable Approaches in Modern Agriculture

Biostimulant application can be considered an effective, practical, and sustainable nutritional crop supplementation and may lessen the environmental problems related to excessive fertilization. Biostimulants provide beneficial properties to plants by increasing plant metabolism, which promotes crop yield and improves the quality of crops; protecting plants against environmental stresses such as water shortage, soil salinization, and exposure to sub-optimal growth temperatures; and promoting plant growth via higher nutrient uptake. Other important benefits include promoting soil enzymatic and microbial activities, changing the architecture of roots, increasing the solubility and mobility of micronutrients, and enhancing the fertility of the soil, predominantly by nurturing the development of complementary soil microbes. Biostimulants are classified as microbial, such as arbuscular mycorrhizae fungi (AMF), plant-growth-promoting rhizobacteria (PGPR), non-pathogenic fungi, protozoa, and nematodes, or non-microbial, such as seaweed extract, phosphite, humic acid, other inorganic salts, chitin and chitosan derivatives, protein hydrolysates and free amino acids, and complex organic materials. Arbuscular mycorrhizal fungi are among the most prominent microbial biostimulants and have an important role in cultivating better, healthier, and more functional foods in sustainable agriculture. AMF assist plant nutrient and water acquisition; enhance plant stress tolerance against salinity, drought, and heavy metals; and reduce soil erosion. AMF are proven to be a sustainable and environmentally friendly source of crop supplements. The current manuscript gives many examples of the potential of biostimulants for the production of different crops. However, further studies are needed to better understand the effectiveness of different biostimulants in sustainable agriculture. The review focuses on how AMF application can overcome nutrient limitations typical of organic systems by improving nutrient availability, uptake, and assimilation, consequently reducing the gap between organic and conventional yields. The aim of this literature review is to survey the impacts of AMF by presenting case studies and successful paradigms in different crops as well as introducing the main mechanisms of action of the different biostimulant products.

Distinct impact of arbuscular mycorrhizal isolates on tomato plant tolerance to drought combined with chronic and acute heat stress

Arbuscular mycorrhizal (AM) fungi could mitigate individual drought and heat stress in host plants. However, there are still major gaps in our understanding of AM symbiosis response to the combined stresses. Here, we compared seven AM fungi, Rhizophagus irregularis, Funneliformis mosseae, Funneliformis geosporum, Funneliformis verruculosum, Funneliformis coronatum, Septoglomus deserticola, Septoglomus constrictum, distributed to many world regions in terms of their impacts on tomato endurance to combined drought and chronic heat as well as combined drought and heat shock. A multidisciplinary approach including morphometric, ecophysiological, biochemical, targeted metabolic (by ultrahigh-performance LC-MS), and molecular analyses was applied. The variation among AM fungi isolates in the enhancement in leaf water potential, stomatal conductance, photosynthetic activity, and maximal PSII photochemical efficiency, proline accumulation, antioxidant enzymes (POD, SOD, CAT), and lowered ROS markers (H2O2, MDA) in host plants under combined stresses were observed. S. constrictum inoculation could better enhanced the host plant physiology and biochemical parameters, while F. geosporum colonization less positively influenced the host plants than other treatments under both combined stresses. F. mosseae- and S. constrictum-associated plants showed the common AM-induced modifications and AM species-specific alterations in phytohormones (ABA, SA, JA, IAA), aquaporin (SlSIP1-2; SlTIP2-3; SlNIP2-1; SlPIP2-1) and abiotic stress-responsive genes (SlAREB1, SlLEA, SlHSP70, SlHSP90) in host plants under combined stresses. Altogether, mycorrhizal mitigation of the negative impacts of drought + prolonged heat and drought + acute heat, with the variation among different AM fungi isolates, depending on the specific combined stress and stress duration.

Chitosan nanoparticles support the impact of arbuscular mycorrhizae fungi on growth and sugar metabolism of wheat crop

Arbuscular mycorrhizae fungi (AMF) symbiosis is an indispensable approach in sustainable agriculture. AMF-plant association is likely to be enhanced by the nanoparticle's application. Herein, the impact of chitosan nanoparticles (CSNPs) on the mycorrhizal colonization in wheat has been investigated. The provoked changes in wheat growth, physiology and metabolism were assessed. CSNPs treatment improved AMF colonization (52 %) by inducing the levels of auxins and strigolactones in roots by 32 and 21 %, respectively besides flavonoids exudation into the rhizosphere (9 %). Such supporting action of CSNPs was associated with improved plant biomass production (21 %) compared to AMF treatment. Both treatments synergistically enhanced the photochemical efficiency of photosystem II and stomatal conductance, therefore the photosynthetic rate was increased. The combined application of CSNPs and AMF enhanced accumulation of glucose, fructose, sucrose, and starch (12, 22, 31 and 13 %, respectively), as well as the activities of sucrose-p-synthase, invertases and starch synthase compared to AMF treatment. The synchronous application of CSNPs and AMF promoted the levels of polyphenols, carotenoids, and tocopherols therefore, improved antioxidant capacity (33 %), in the roots. CSNPs can be applied as an efficient biofertilization strategies to enhance plant growth and fitness, beside improvement of health promoting compounds in wheat.

The new isolated Archaea strain improved grain yield, metabolism and quality of wheat plants under Co stress conditions

Heavy metal (e.g. cobalt) pollution causes a serious of environmental and agricultural problems. On the other hand, plant growth-promoting microorganisms enhance plant growth and mitigate heavy metal stress. Herein, we isolated and identified the unclassified species strain NARS9, belong to Haloferax,. Cobalt (Co, 200 mg/kg soil) stress mitigating impact of the identified on wheat grains yield, primary and secondary metabolism and grain quality was investigated. Co alone significantly induced Co accumulation in wheat grain (260%), and consequently reduced wheat yield (130%) and quality. Haloferax NARS9 alone significantly enhanced grain chemicals composition (i.e., total sugars (89%) and organic acids (e.g., oxalic and isobutyric acids), essential amino acids (e.g., threonine, lysine, and histidine) and unsaturated fatty acids (e.g. eicosenoic, erucic and tetracosenoic acids). Interestingly, Co stress induced wheat grain yield, reduction were significantly mitigated by Haloferax NARS9 treatment by 26% compared to Co stress alone. Under Co stress, Haloferax NARS9 significantly increased sugar metabolism including sucrose and starch levels and their metabolic enzymes (i.e. invertases, sucrose synthase, starch synthase). This in turn increased organic acid (e.g. oxalic (70%) and malic acids (60%)) and amino acids. levels and biosynthetic enzymes, e.g. glutamine synthetase and threonine synthase. Increased sugars levels by Haloferax NARS9 under Co treatment also provided a route for the biosynthesis of saturated fatty acids, particularly palmitic and stearic acids. Furthermore, Haloferax NARS9 treatment supported the wheat nutritive value through increasing minerals (Ca, Fe, Mn, Zn) and antioxidants i.e., polyphenol, flavonoids, ASC and GSH and total polyamines by 50%, 110%, 400%, 30%, and 90% respectively). These in parallel with the increase in the activity of (phenylalanine ammonia-lyase (110%) in phenolic metabolism). Overall, this study demonstrates the potentiality of Haloferax NARS9 in harnessing carbon and nitrogen metabolism differentially in wheat plants to cope with Co toxicity. Our results also suggested that the use of Haloferax NARS9 in agricultural fields can improve growth and nutritional value of wheat grains.

Plant secondary metabolic responses to global climate change: A meta-analysis in medicinal and aromatic plants

Plant secondary metabolites (SMs) play crucial roles in plant-environment interactions and contribute greatly to human health. Global climate changes are expected to dramatically affect plant secondary metabolism, yet a systematic understanding of such influences is still lacking. Here, we employed medicinal and aromatic plants (MAAPs) as model plant taxa and performed a meta-analysis from 360 publications using 1828 paired observations to assess the responses of different SMs levels and the accompanying plant traits to elevated carbon dioxide (eCO₂ ), elevated temperature (eT), elevated nitrogen deposition (eN) and decreased precipitation (dP). The overall results showed that phenolic and terpenoid levels generally respond positively to eCO₂ but negatively to eN, while the total alkaloid concentration was increased remarkably by eN. By contrast, dP promotes the levels of all SMs, while eT exclusively exerts a positive influence on the levels of phenolic compounds. Further analysis highlighted the dependence of SM responses on different moderators such as plant functional types, climate change levels or exposure durations, mean annual temperature and mean annual precipitation. Moreover, plant phenolic and terpenoid responses to climate changes could be attributed to the variations of C/N ratio and total soluble sugar levels, while the trade-off supposition contributed to SM responses to climate changes other than eCO₂ . Taken together, our results predicted the distinctive SM responses to diverse climate changes in MAAPs and allowed us to define potential moderators responsible for these variations. Further, linking SM responses to C-N metabolism and growth-defence balance provided biological understandings in terms of plant secondary metabolic regulation.

Interactive influence of elevated CO2 and arbuscular mycorrhizal fungi on sucrose and coumarin metabolism in Ammi majus

The elevated level of CO₂ (eCO₂) and arbuscular mycorrhizal fungi (AMF) have been known as successful eco-friendly agents for plant growth and development as well as quality enhancers. The current investigation was designed to study the influence of eCO₂ (620 μmol CO₂ mol^-1 air) and AMF on sucrose and phenylpropanoid metabolism, including coumarins, the most important bioactive metabolite in Ammi majus. eCO₂ and AMF were applied, and different parameters have been assessed in A. majus such as changes in mycorrhizal colonization, plant biomass production, photosynthesis, and levels of N, P, and Ca besides the key metabolites and enzymes in sucrose and coumarins metabolic pathways. The present outcomes revealed that eCO₂ and AMF individually or combined enhanced the plant biomass and photosynthesis as well as nutrient concentrations. Furthermore, the levels of sucrose, soluble sugars, glucose, fructose, and the activities of some key enzymes in their metabolism besides phenylpropanoids metabolites in shoot and root of A. majus have been enhanced by eCO₂ and AMF especially when combined. Moreover, upregulation of sucrose is linked to phenylpropanoids metabolic pathway via upregulation of phenylalanine ammonia-lyase activity suggesting high coumarin biosynthesis. Generally, the synergistic effect of both treatments was noted for most of the investigated parameters compared to the individual effect. It could be concluded that the combined application of eCO₂ and AMF affects A. majus global metabolism and induces accumulation of phyto-molecules, coumarin, which might improve its medicinal and pharmacological applications.

Multiple Arbuscular Mycorrhizal Fungal Consortia Enhance Yield and Fatty Acids of Medicago sativa: A Two-Year Field Study on Agronomic Traits and Tracing of Fungal Persistence

Arbuscular mycorrhizal fungi are promoted as biofertilizers due to potential benefits in crop productivity, and macro- and microelement uptake. However, crop response to arbuscular mycorrhizal fungi (AMF) inoculation is context-dependent, and AMF diversity and field establishment and persistence of inoculants can greatly contribute to variation in outcomes. This study was designed to test the hypotheses that multiple and local AMF inoculants could enhance alfalfa yield and fatty acids (FA) compared to exotic isolates either single or in the mixture. We aimed also to verify the persistence of inoculated AMF, and which component of the AMF communities was the major driver of plant traits. Therefore, a field experiment of AMF inoculation of alfalfa (Medicago sativa L.) with three single foreign isolates, a mixture of the foreign isolates (FMix), and a highly diverse mixture of local AMF (LMix) was set up. We showed that AMF improved alfalfa yield (+ 68%), nutrient (+ 147% N content and + 182% P content in forage), and FA content (+ 105%). These positive effects persisted for at least 2 years post-inoculation and were associated with enhanced AMF abundance in roots. Consortia of AMF strains acted in synergy, and the mixture of foreign AMF isolates provided greater benefits compared to local consortia (+ 20% forage yield, + 36% forage N content, + 18% forage P content, + 20% total FA in forage). Foreign strains of Funneliformis mosseae and Rhizophagus irregularis persisted in the roots of alfalfa 2 years following inoculation, either as single inoculum or as a component of the mixture. Among inoculants, F. mosseae BEG12 and AZ225C and the FMix exerted a higher impact on the local AMF community compared with LMix and R. irregularis BEG141. Finally, the stimulation of the proliferation of a single-taxa (R. irregularis cluster1) induced by all inoculants was the main determinant of the host benefits. Crop productivity and quality as well as field persistence of inoculated AMF support the use of mixtures of foreign AMF. On the other hand, local mixtures showed a lower impact on native AMF. These results pave the way for extending the study on the effect of AMF mixtures for the production of high-quality forage for the animal diet.

Effect of arbuscular mycorrhizal fungi in roots on antioxidant enzyme activity in leaves of Robinia pseudoacacia L. seedlings under elevated CO2 and Cd exposure

Arbuscular mycorrhizal fungi (AMF) are easily influenced by increasing atmospheric CO₂ concentration and heavy metals including cadmium (Cd), which can regulate antioxidant enzyme in host plants. Although the effect of AMF under individual conditions such as elevated CO₂ (ECO₂) and Cd on antioxidant enzyme in host plants has been reported widely, the effect of AMF under ECO₂ + Cd receives little attention. In this study, a pot experiment was conducted to study the effect of AMF community in roots on superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities in leaves of 135-d Robinia pseudoacacia L. seedlings under ECO₂ + Cd. The activities of SOD and CAT increased and POD activity and the richness and diversity of AMF community decreased under ECO₂ + Cd relative to Cd alone. The richness and diversity of AMF were negatively related to Cd content in roots and leaves. The richness and OTUs of AMF community positively and AMF gene abundance negatively affected POD activity under the combined treatments. Superoxide dismutase and POD activities were negatively and positively related to Archaeospora and Scutellospora, respectively, under ECO₂ + Cd. Cadmium in roots and leaves was negatively and significantly related to Glomus, Scutellospora, and Claroideoglomus abundance under ECO₂ + Cd. Overall, AMF diversity and Archaeospora and Scutellospora in roots significantly influenced SOD, POD, and CAT activities. The response of AM symbiosis to ECO₂ might regulate antioxidant capacity in host plants upon Cd exposure. Glomus, Scutellospora, and Claroideoglomus might be applied to phytoremediation of Cd-contaminated soils.

Innovating the Synergistic Assets of β-Amino Butyric Acid (BABA) and Selenium Nanoparticles (SeNPs) in Improving the Growth, Nitrogen Metabolism, Biological Activities, and Nutritive Value of Medicago interexta Sprouts

In view of the wide traditional uses of legume sprouts, several strategies have been approved to improve their growth, bioactivity, and nutritive values. In this regard, the present study aimed at investigating how priming with selenium nanoparticles (SeNPs, 25 mg L^-1) enhanced the effects of β-amino butyric acid (BABA, 30 mM) on the growth, physiology, nitrogen metabolism, and bioactive metabolites of Medicago interexta sprouts. The results have shown that the growth and photosynthesis of M. interexta sprouts were enhanced by the treatment with BABA or SeNPs, being higher under combined treatment. Increased photosynthesis provided the precursors for the biosynthesis of primary and secondary metabolites. In this regard, the combined treatment had a more pronounced effect on the bioactive primary metabolites (essential amino acids), secondary metabolites (phenolics, GSH, and ASC), and mineral profiles of the investigated sprouts than that of sole treatments. Increased amino acids were accompanied by increased nitrogen metabolism, i.e., nitrate reductase, glutamate dehydrogenase (GDH), glutamate synthase (GOGAT), glutamine synthase (GS), cysteine synthesis serine acetyltransferase, arginase, threonine synthase, and methionine synthase. Further, the antioxidant capacity (FRAP), the anti-diabetic activities (i.e., α-amylase and α-glucosidase inhibition activities), and the glycemic index of the tested sprouts were more significantly improved by the combined treatment with BABA and SeNPs than by individual treatment. Overall, the combined effect of BABA and SeNPs could be preferable to their individual effects on plant growth and bioactive metabolites.

Bacterial Endophytes as a Promising Approach to Enhance the Growth and Accumulation of Bioactive Metabolites of Three Species of Chenopodium Sprouts

Sprouts are regarded as an untapped source of bioactive components that display various biological properties. Endophytic bacterium inoculation can enhance plant chemical composition and improve its nutritional quality. Herein, six endophytes (Endo 1 to Endo 6) were isolated from Chenopodium plants and morphologically and biochemically identified. Then, the most active isolate Endo 2 (strain JSA11) was employed to enhance the growth and nutritive value of the sprouts of three Chenopodium species, i.e., C. ambrosoides, C. ficifolium, and C. botrys. Endo 2 (strain JSA11) induced photosynthesis and the mineral uptake, which can explain the high biomass accumulation. Endo 2 (strain JSA11) improved the nutritive values of the treated sprouts through bioactive metabolite (antioxidants, vitamins, unsaturated fatty acid, and essential amino acids) accumulation. These increases were correlated with increased amino acid levels and phenolic metabolism. Consequently, the antioxidant activity of the Endo 2 (strain JSA11)-treated Chenopodium sprouts was enhanced. Moreover, Endo 2 (strain JSA11) increased the antibacterial activity against several pathogenic bacteria and the anti-inflammatory activities as evidenced by the reduced activity of cyclooxygenase and lipoxygenase. Overall, the Endo 2 (strain JSA11) treatment is a successful technique to enhance the bioactive contents and biological properties of Chenopodium sprouts.

Developmental Stages-Specific Response of Anise Plants to Laser-Induced Growth, Nutrients Accumulation, and Essential Oil Metabolism

Compared to seeds and mature tissues, sprouts are well known for their higher nutritive and biological values. Fruits of Pimpinella anisum (anise) are extensively consumed as food additives; however, the sprouting-induced changes in their nutritious metabolites are hardly studied. Herein, we investigated the bioactive metabolites, phytochemicals, and antioxidant properties of fruits, sprouts (9-day-old), and mature tissue (5-week-old) of anise under laser irradiation treatment (He-Ne laser, 632 nm). Laser treatment increased biomass accumulation of both anise sprouts and mature plants. Bioactive primary (e.g., proteins and sugars) and secondary metabolites (e.g., phenolic compounds), as well as mineral levels, were significantly enhanced by sprouting and/or laser light treatment. Meanwhile, laser light has improved the levels of essential oils and their related precursors (e.g., phenylalanine), as well as enzyme activities [e.g., O-methyltransferase and 3-Deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHPS)] in mature tissues. Moreover, laser light induced higher levels of antioxidant and anti-lipidemic activities in sprouts as compared to fruits and mature tissues. Particularly at the sprouting stage, anise was more responsive to laser light treatment than mature plants.

Effect of Elevated CO2 on Biomolecules' Accumulation in Caraway (Carum carvi L.) Plants at Different Developmental Stages

Caraway plants have been known as a rich source of phytochemicals, such as flavonoids, monoterpenoid glucosides and alkaloids. In this regard, the application of elevated CO₂ (eCO₂) as a bio-enhancer for increasing plant growth and phytochemical content has been the focus of many studies; however, the interaction between eCO₂ and plants at different developmental stages has not been extensively explored. Thus, the present study aimed at investigating the changes in growth, photosynthesis and phytochemicals of caraway plants at two developmental stages (sprouts and mature tissues) under control and increased CO₂ conditions (ambient CO₂ (a CO₂, 400 ± 27 μmol CO₂ mol^-1 air) and eCO₂, 620 ± 42 μmol CO₂ mol^-1 air ppm). Moreover, we evaluated the impact of eCO₂-induced changes in plant metabolites on the antioxidant and antibacterial activities of caraway sprouts and mature plants. CO₂ enrichment increased photosynthesis and biomass accumulation of both caraway stages. Regarding their phytochemical contents, caraway plants interacted differently with eCO₂, depending on their developmental stages. High levels of CO₂ enhanced the production of total nutrients, i.e., carbohydrates, proteins, fats and crude fibers, as well as organic and amino acids, in an equal pattern in both caraway sprouts and mature plants. Interestingly, the eCO₂-induced effect on minerals, vitamins and phenolics was more pronounced in caraway sprouts than the mature tissues. Furthermore, the antioxidant and antibacterial activities of caraway plants were enhanced under eCO₂ treatment, particularly at the mature stage. Overall, eCO₂ provoked changes in the phytochemical contents of caraway plants, particularly at the sprouting stage and, hence, improved their nutritive and health-promoting properties.

Establishment of actinobacteria-Satureja hortensis interactions under future climate CO2-enhanced crop productivity in drought environments of Saudi Arabia

Drought is a significant global constraint on agricultural production and food security. As a promising approach to improve plant growth and yield under challenging conditions, plant growth-promoting actinobacteria has attracted much interest. Further, elevated levels of atmospheric CO2 (eCO2) may promote the plant-actinobacteria interactions which could be effective to improve the plant growth for food production. Herein, we have investigated the impact of actinobacteria and/or CO2 on biomass production, photosynthesis, macronutrients, levels of organic acids, amino acids, and essential oils as well as antioxidant activities of Satureja hortensis under water-deficit conditions. Among different actinobacterial isolates evaluated for development of secondary metabolites and biological activities, Ac9 was highly capable of producing flavonoids, and it also showed high antioxidant and microbial activities. It markedly induced the plant growth, photosynthesis, and global metabolic improvement, under water-deficit conditions. Interestingly, treatment with Ac9 in combination with eCO2 substantially minimized drought stress-induced biomass and photosynthesis reductions in Satureja hortensis. Improved photosynthesis by Ac9 and/or eCO2 induced the primary and secondary metabolisms in drought-stressed plants. The levels of the majority of the detected organic acids, essential oil, and amino acids were further improved as a result of the synergistic action of Ac9 and eCO2, as compared to the individual treatments. Furthermore, Ac9 or eCO2 significantly improved the antioxidant activities in stressed plants; however, much more positive impact was obtained by their synchronous application. Thus, the current study suggests that actinobacterial treatment induces global metabolic changes in water-stressed Satureja hortensis, the effects that have been much more strengthened under eCO2.

Arbuscular mycorrhizal fungi, a key symbiosis in the development of quality traits in crop production, alone or combined with plant growth-promoting bacteria

Modern agriculture is currently undergoing rapid changes in the face of the continuing growth of world population and many ensuing environmental challenges. Crop quality is becoming as important as crop yield and can be characterised by several parameters. For fruits and vegetables, quality descriptors can concern production cycle (e.g. conventional or organic farming), organoleptic qualities (e.g. sweet taste, sugar content, acidity) and nutritional qualities (e.g. mineral content, vitamins). For other crops, however, the presence of secondary metabolites such as anthocyanins or certain terpenes in the targeted tissues is of interest as well, especially for their human health properties. All plants are constantly interacting with microorganisms. These microorganisms include arbuscular mycorrhizal fungi as well as certain soil bacteria that provide ecosystem services related to plant growth, nutrition and quality parameters. This review is an update of current research on the single and combined (co-inoculation) use of arbuscular mycorrhizal fungi and plant growth-promoting rhizobacteria in crop production, with a focus on their positive impacts on crop quality traits (e.g. nutritional value, organoleptic properties). We also highlight the need to dissect mechanisms regulating plant-symbionts and symbiont-symbiont interactions, to develop farming practices and to study a broad range of interactions to optimize the symbiotic potential of root-associated microorganisms.

Root mass carbon costs to acquire nitrogen are determined by nitrogen and light availability in two species with different nitrogen acquisition strategies

Plant nitrogen acquisition requires carbon to be allocated belowground to build roots and sustain microbial associations. This carbon cost to acquire nitrogen varies by nitrogen acquisition strategy; however, the degree to which these costs vary due to nitrogen availability or demand has not been well tested under controlled conditions. We grew a species capable of forming associations with nitrogen-fixing bacteria (Glycine max) and a species not capable of forming such associations (Gossypium hirsutum) under four soil nitrogen levels to manipulate nitrogen availability and four light levels to manipulate nitrogen demand in a full-factorial greenhouse experiment. We quantified carbon costs to acquire nitrogen as the ratio of total root carbon to whole-plant nitrogen within each treatment combination. In both species, light availability increased carbon costs due to a larger increase in root carbon than whole-plant nitrogen, while nitrogen fertilization generally decreased carbon costs due to a larger increase in whole-plant nitrogen than root carbon. Nodulation data indicated that G. max shifted relative carbon allocation from nitrogen fixation to direct uptake with increased nitrogen fertilization. These findings suggest that carbon costs to acquire nitrogen are modified by changes in light and nitrogen availability in species with and without associations with nitrogen-fixing bacteria.

Funneliformis mosseae Improves Growth and Nutrient Accumulation in Wheat by Facilitating Soil Nutrient Uptake under Elevated CO2 at Daytime, Not Nighttime

The concurrent effect of elevated CO₂ (eCO₂) concentrations and arbuscular mycorrhizal fungi (AMF) on plant growth, carbon (C), nitrogen (N), phosphorus (P) and potassium (K) accumulations in plant and soil is largely unknown. To understand the mechanisms of eCO₂ and mycorrhization on wheat (Triticum aestivum) performance and soil fertility, wheat seedlings were grown under four different CO₂ environments for 12 weeks, including (1) ambient CO₂ (ACO₂, 410/460 ppm, daytime/nighttime), (2) sole daytime eCO₂ (DeCO₂, 550/460 ppm), (3) sole nighttime eCO₂ (NeCO₂, 410/610 ppm), and (4) dual or continuous daytime/nighttime eCO₂ ((D + N)eCO₂, 550/610 ppm), and with or without AMF (Funneliformis mosseae) colonization. DeCO₂, NeCO₂ and (D + N)eCO₂ generally significantly increased shoot and root biomass, plant C, N, P and K accumulation, soil invertase and urease activity, but decreased shoot and root N, P and K concentrations, and soil available N, P and K. Compared with non-AMF, AMF effects on above-mentioned characteristics were significantly positive under ACO₂, DeCO₂ and (D + N)eCO₂, but negative on plant biomass, C, N, P and K accumulation under NeCO₂. Overall, AMF colonization alleviated soil nutrient constraints on plant responses to DeCO₂, while NeCO₂ decreased AMF's beneficial effects on plants. These results demonstrated that an integration of AMF's benefits to plants under factual field DeCO₂ and/or NeCO₂ will be critical for managing the long-term consequence of future CO₂ rising on global cropping systems.

Arbuscular Mycorrhization Enhances Nitrogen, Phosphorus and Potassium Accumulation in Vicia faba by Modulating Soil Nutrient Balance under Elevated CO2

Effects of arbuscular mycorrhizal fungi (AMF), elevated carbon dioxide (eCO₂), and their interaction on nutrient accumulation of leguminous plants and soil fertility is unknown. Plant growth, concentrations of tissue nitrogen (N), phosphorus (P), and potassium (K) in 12-week-old nodulated faba bean (Vicia faba, inoculated with Rhizobium leguminosarum bv. NM353), and nutrient use efficiency were thus assessed under ambient CO₂ (410/460 ppm, daytime, 07:00 a.m.–19:00 p.m./nighttime, 19:00 p.m.–07:00 a.m.) and eCO₂ (550/610 ppm) for 12 weeks with or without AM fungus of Funneliformis mosseae inoculation. eCO₂ favored AMF root colonization and nodule biomass production. eCO₂ significantly decreased shoot N, P and K concentrations, but generally increased tissue N, P and K accumulation and their use efficiency with an increased biomass production. Meanwhile, eCO₂ enhanced C allocation into soil but showed no effects on soil available N, P, and K, while AM symbiosis increased accumulation of C, N, P, and K in both plant and soil though increased soil nutrient uptake under eCO₂. Moreover, plant acquisition of soil NO₃⁻–N and NH₄⁺–N respond differently to AMF and eCO₂ treatments. As a result, the interaction between AM symbiosis and eCO₂ did improve plant C accumulation and soil N, P, and K uptake, and an alternative fertilization for legume plantation should be therefore taken under upcoming atmosphere CO₂ rising. Future eCO₂ studies should employ multiple AMF species, with other beneficial fungal or bacterial species, to test their interactive effects on plant performance and soil nutrient availability in the field, under other global change events including warming and drought.

Bioactive Potential of Several Actinobacteria Isolated from Microbiologically Barely Explored Desert Habitat, Saudi Arabia

Simple Summary

Bioactive natural products have been regarded as promising tools for treatment of various ailments. Among natural sources, actinomycetes have been widely explored for their potential bioactivity. In this regard, the present study has focused on the phytochemical content and biological activities of several actinobacteria isolates, which were investigated for their phenolic and flavonoid content, as well as their antioxidant, antibacterial and antiprotozoal activities. The most active isolates were further investigated for their antileukemic activity, where such isolates were shown to exert cytotoxic activity against the tested cell lines, following a mechanism that might be due to the ability of the active isolate extracts to reduce cyclooxygenase and lipoxygenase activities. Overall, isolation and characterization of the active molecule from the potential actinomycetes strains will pave the way for the development of drugs against human diseases such as blood cancer.

Abstract

Biomolecules from natural sources, including microbes, have been the basis of treatment of human diseases since the ancient times. Therefore, this study aimed to investigate the potential bioactivity of several actinobacteria isolates form Al-Jouf Desert, Saudi Arabia. Twenty-one actinobacterial isolates were tested for their antioxidant (flavonoids, phenolics, tocopherols and carotenoids) content, and biological activities, namely FRAP, DPPH, ABTS, SOS and XO inhibition, anti-hemolytic and anti-lipid peroxidation as well as their antibacterial and antiprotozoal activities. Accordingly, five isolates (i.e., Act 2, 12, 15, 19 and 21) were selected and their 90% ethanolic extracts were used. The phylogenetic analysis of the 16S rRNA sequences indicated that the most active isolates belong to genus Streptomyces. The genus Streptomyces has been documented as a prolific producer of biologically active secondary metabolites against different cancer types. Thus, the anti-blood cancer activity and the possible molecular mechanisms by which several Streptomyces species extracts inhibited the growth of different leukemia cells, i.e., HL-60, K562 and THP-1, were investigated. In general, the five active isolates showed cytotoxic activity against the tested cell lines in a dose dependent manner. Among the potent isolates, isolate Act 12 significantly decreased the cell viability and showed maximum cytotoxic activities against both HL-60 and K562 cells, while isolate Act 15 exhibited maximum cytotoxic activity against THP-1 cells. Moreover, Act 2 and Act 12 reduced cyclooxygenase (COX-2) and lipoxygenase (LOX) activity, which is involved in the proliferation and differentiation of cancer cells and may represent a possible molecular mechanism underlying leukemia growth inhibition. The bioactive antioxidant extracts of the selected Streptomyces species inhibited leukemia cell growth by reducing the COX-2 and LOX activity. Overall, our study not only introduced a promising natural alternative source for anticancer agents, but it also sheds light on the mechanism underlying the anticancer activity of isolated actinomycetes.

Arbuscular Mycorrhizal Fungi Improve Tolerance of the Medicinal Plant Eclipta prostrata (L.) and Induce Major Changes in Polyphenol Profiles Under Salt Stresses

Eclipta prostrata (L.) is an important and well-known medicinal plant due to its valuable bioactive compounds. Microorganisms, including arbuscular mycorrhizal fungi (AMF), and salinity could directly impact plant metabolome, thus influencing their secondary metabolites and the efficacy of herbal medicine. In this study, the role of different single AMF species (Funneliformis mosseae, Septoglomus deserticola, Acaulospora lacunosa) and a mixture of six AMF species in plant growth and physio-biochemical characteristics of E. prostrata under non-saline conditions was investigated. Next, the most suitable AM treatment was chosen to examine the impact of AMF on physio-biochemical features and polyphenol profiles of E. prostrata under saline conditions (100 and 200 mM NaCl). The findings indicated that AMF mixture application resulted in more effective promotion on the aboveground part of non-saline plants than single AMF species. AM mixture application improved growth and salt tolerance of E. prostrata through increasing the activity of catalase, peroxidase (at 4 weeks), proline, and total phenolic content (at 8 weeks). Such benefits were not observed under high salinity, except for a higher total phenolic concentration in mycorrhizal plants at 8 weeks. Through high-performance liquid chromatography, 14 individual phenolic compounds were analyzed, with wedelolactone and/or 4,5-dicaffeoylquinic acid abundant in all treatments. Salinity and mycorrhizal inoculation sharply altered the polyphenol profiles of E. prostrata. Moderate salinity boosted phenolic compound production in non-AM plants at 4 weeks, while at 8 weeks, the decline in the content of phenolic compounds occurred in uncolonized plants subjected to both saline conditions. Mycorrhization augmented polyphenol concentration and yield under non-saline and saline conditions, depending on the growth stages and salt stress severity. Plant age influenced polyphenol profiles with usually a higher content of phenolic compounds in older plants and changed the production of individual polyphenols of both non-AM and AM plants under non-stress and salt stress conditions. A better understanding of factors (involving mycorrhiza and salinity) affecting the phenolic compounds of E. prostrata facilitates the optimization of individual polyphenol production in this medicinal plant.

Laser light as a promising approach to improve the nutritional value, antioxidant capacity and anti-inflammatory activity of flavonoid-rich buckwheat sprouts

Buckwheat sprouts are rich in several nutrients such as antioxidant flavonoids that have a positive impact on human health. Although there are several studies reported the positive impact of laser light on crop plants, no studies have applied laser light to enhance the nutritive values of buckwheat sprouts. Herein, the contents of health-promoting minerals, metabolites and enzymes as well as the antioxidant and anti-inflammatory activities were determined in laser-treated (He-Ne laser, 632 nm, 5 mW) common buckwheat (CBW) and tartarybuckwheat (TBW) sprouts. Out of 49 targeted minerals, vitamins, pigments and antioxidants, more than 35 parameters were significantly increased in CBW and/or TBW sprouts by laser light treatment. Also, laser light boosted the antioxidant capacity and anti-inflammatory activities through inhibiting cyclooxygenase-2 and lipoxygenase activities, particularly in TBW sprouts. Accordingly, laser light could be recommended as a promising method to improve the nutritional and health-promoting values of buckwheat sprouts.

Interactive Impact of Arbuscular Mycorrhizal Fungi and Elevated CO2 on Growth and Functional Food Value of Thymus vulgare

Arbuscular mycorrhizal fungi (AMF) and elevated CO₂ (eCO₂) have been effectively integrated to the agricultural procedures as an ecofriendly approach to support the production and quality of plants. However, less attention has been given to the synchronous application of AMF and eCO₂ and how that could affect the global plant metabolism. This study was conducted to investigate the effects of AMF and eCO₂, individually or in combination, on growth, photosynthesis, metabolism and the functional food value of Thymus vulgare. Results revealed that both AMF and eCO₂ treatments improved the photosynthesis and biomass production, however much more positive impact was obtained by their synchronous application. Moreover, the levels of the majority of the detected sugars, organic acids, amino acids, unsaturated fatty acids, volatile compounds, phenolic acids and flavonoids were further improved as a result of the synergistic action of AMF and eCO₂, as compared to the individual treatments. Overall, this study clearly shows that co-application of AMF and eCO₂ induces a synergistic biofertilization impact and enhances the functional food value of T. vulgare by affecting its global metabolism.