Induction Of Secondary Metabolites Research Articles

Silicon improves the drought tolerance in pepper plants through the induction of secondary metabolites, GA biosynthesis pathway, and suppression of chlorophyll degradation

Drought stress caused by the global climate considerably disturbs plant yield and growth. Here, we explored the putative roles of silicon in repressing drought mechanisms in pepper and the prominent involvement of secondary metabolites, GA pathway, and photosystem II. Our research revealed that the transcript level of the flavonoid biosynthesis-associated genes, including the PAL, 4-CL, CHS, FLS-1, F3H and DFR, progressively induced in the pepper leaves treated with silicon during the drought stress duration. Moreover, the phenolic and flavonoid compounds extensively induced in the pepper plants. Furthermore, the pepper plants markedly inhibited chlorophyll catabolic-allied genes, senescence-related marker gene, and the Rbohs gene. Silicon application also sustained the membrane stability, supported via fewer electrolyte leakage processes and minor, O2– H2O2 and MDA levels during drought. Apart from this, the pepper plants significantly induced the expression level of the photosystem II-related genes, osmoprotectants pathway-associated genes, and antioxidant defense genes. Moreover, the GA biosynthesis genes were prompted, while the ABA signaling and biosynthesis genes were suppressed in the silicon-supplemented plants. These consequences infer that the role of Si supplementation on enhancing drought tolerance could be elucidated through the activation of secondary metabolites, flavonoid biosynthesis, osmoprotectants, GA pathway, the efficiency of PSII, and the suppression of chlorophyll degradation. Our research outcomes unveil new and remarkable characteristics of silicon supplementation and offer a series of candidate targets for improving the tolerance of pepper plants to drought stress.

MOLECULAR CHARACTERIZATION OF MYCORRHIZA AND ITS POTENTIAL AS BIOCONTROL

Orchid mycorrhizal fungi (OMF) are vital biocontrol agents, especially for Odontoglossum ringspot virus (ORSV). The promising study helped identify the mycorrhiza isolate from native tropical orchids and determine its potential as a biocontrol. Sample collection of healthy roots of Phalaenopsis amabilis emanated in Yogyakarta, Indonesia, carrying out molecular identification with rDNA-ITS amplification using a set of universal primers ITS1 and ITS4. In vivo, antagonist tests began by inoculating viruses and mycorrhiza to determine the effect of growth and induction of secondary metabolites. The result showed one isolate of Trichoderma sp. associated with the molecular analysis has amplified the ITS1- 5.8S-ITS4 section by 600–750 bp DNA. The sequenced products revealed insertion and substitution occurrences, which may have caused the variance by strain diversity and potential severity. Indonesian isolates have undergone speciation and separation from other isolates by a substantial distance. The considerable effects were the increase in leaf length, leaf width, root length, leaf count, the number of roots, fresh weight, and a lowering of the virus content. The analysis of the plant growth parameters and virus concentrations provided significant differences among the treatments inoculated with orchid mycorrhiza (Mycorrhiza [M], Mycorrhiza + Virus [MV], and Virus + Mycorrhiza [VM]) and those without orchid mycorrhiza inoculation (Control [C] and Virus [V]). The orchid resistance suggested that the virus infecting plant leaves contain more phenolic chemicals. This study is the first-ever report of the Trichoderma sp. isolated from native tropical orchids in Indonesia.

Biocontrol of Fusarium wilt disease by endophytic Bacillus xiamenensis BS10 isolated from the root nodules of Brassica nigra (mustard plant) and analysis of defence molecular biomarkers in the greenhouse and field trial

Endophytic bacteria possess positive effects on their host plants, including, secondary metabolite induction, disease-resistance improvement, and growth promotion. Bacillus spp. are considered to be an eco-friendly and bio-safe alternative to traditional chemical fungicides. In our study, a collection of 12 endophytic bacteria were isolated from Brassica nigra root nodules and analyzed for plant growth-promoting activities. The endophytic strain BS10 significantly solubilise phosphate (19 ± 1 mm halo zone), siderophore (17 ± 1 mm halo zone), HCN (18 ± 1 halo zone), and indole acetic acid (205.1 ± 2.8 μg/mL) significantly (p < 0.05) than other isolates. The antifungal activity of isolated endophytes was analyzed using a dual-culture screening method. The antifungal activity against Fusarium oxysporum revealed that the strain BS10 exhibited maximum activity against F. oxysporum and the inhibition rate ranged from 20 ± 1 to 70.2 ± 3.5 % after 4 days of treatment and increased after 8 days (36.9 ± 3.5–75.8 ± 3.2 %) among other endophytes. The cell-free extract decreased fungal growth and the inhibition rate varied between 12 % and 47 % (p < 0.05). The results revealed that the fungal infection of the mustard plants with wilt disease causing F. oxysporum significantly reduced the growth of the mustard plant, and root, shoot length, and dry weight compared with the control (p < 0.05). The infected plants treated with endophyte showed an improvement in the growth parameters (p < 0.05). The endophytes-treated plants showed fewer symptoms of rot disease in mustard plants. The chlorophyll content (2.27-fold), soluble leaf protein (1.22-fold), proline (26 ± 2.8 nM/g fresh weight) were improved in the plant leaves treated with endophyte. The biosynthesis of ascorbate peroxidase, phenylalanine ammonia-lyase, and catalase was improved in the endophyte-treated seeds compared with control seeds (p > 0.05). The isolated B. xiamenensis is an important resource to biocontrol Fusarium wilt diseases in the mustard plant.

Metabolic Integration of Spectral and Chemical Cues Mediating Plant Responses to Competitors and Herbivores.

Light quality and chemicals in a plant’s environment can provide crucial information about the presence and nature of antagonists, such as competitors and herbivores. Here, we evaluate the roles of three sources of information—shifts in the red:far red (R:FR) ratio of light reflected off of potentially competing neighbors, induced metabolic changes to damage by insect herbivores, and induced changes to volatile organic compounds emitted from herbivore-damaged neighboring plants—to affect metabolic responses in the tall goldenrod, Solidago altissima. We address the hypothesis that plants integrate the information available about competitors and herbivory to optimize metabolic responses to interacting stressors by exposing plants to the different types of environmental information in isolation and combination. We found strong interactions between the exposure to decreased R:FR light ratios and damage on the induction of secondary metabolites (volatile and non-volatile) in plants. Similarly, the perception of VOCs emitted from neighboring plants was altered by the simultaneous exposure to spectral cues from neighbors. These results suggest that plants integrate spectral and chemical environmental cues to change the production and perception of volatile and non-volatile compounds and highlight the role of plant context-dependent metabolic responses in mediating population and community dynamics.

Fat-Rich Food Review on Obesity Control through Induction Enzyme Inhibitors

Background: Obesity is an imbalance between height and weight due to excessive body fat tissue. The purpose of writing this review is to find out the effect of enzyme inhibitor induction on fat-rich foods as control of obesity. Method: Writing and assessing source problems related to using literature study methods. Results: One way of controlling obesity is by regulating dietary patterns and consumption of lipase inhibitors. Inhibition of lipase is one of the most widely developed effective ways in diet medicine. Inhibitory compounds cause pancreatic lipase to lose its ability in decomposition that enters the blood. The potency of plant-origin lipase inhibitor compounds can be increased in both number and performance. Increasing the production of secondary metabolite group inhibitors is by fermentation of microorganisms. Conclusion: Inhibition of triglyceride hydrolysis through inhibition of lipase enzymes can decrease and prevent obesity. Secondary metabolite induction can be fermented with microorganisms. The production of secondary metabolite compounds in medicinal plants can be increased in the presence of fermentation. Flavonoids can decrease the accumulation of lipids in the heart, reduce glucose absorption, inhibit the breakdown of polysaccharides into monosaccharides.

Induction of secondary metabolites on nanoparticles stress in callus culture of Artemisia annua L.

Nanoparticles are known bio elicitors in plant biotechnology. Different concentrations of ZnO, CuO and CoO nanoparticles were used for the enhanced accumulation of secondary metabolites and antioxidant activities in the callus derived from root, shoot and leaf of Artemisia annua L. Biomass of callus was somehow affected on high concentrations of Nps. Phenolic content was observed maximum (60µg) in shoot callus at 0.1mg/l of CuONps. Total antioxidant activity was observed maximum (33µg) in root callus at 0.1mg/l of ZnOnps. Total reducing power maximum (33µg) was observed in root callus at concentration of 0.05 mg/l of CoONps. Maximum radical scavenging activity was observed in shoot callus at 0.05mg/l of ZnONps. Rutin gallic acid and caffic acid were also determined in most of the samples by HPLC. The study concludes that different Nps have positive effect on the induction of secondary metabolites in A.annua plant.

Whole fungal elicitors boost paclitaxel biosynthesis induction in Corylus avellana cell culture.

Paclitaxel is an effective natural-source chemotherapeutic agent commonly applied to treat a vast range of cancers. In vitro Corylus avellana culture has been reported as a promising and inexpensive system for paclitaxel production. Fungal elicitors have been made known as the most efficient strategy for the biosynthesis induction of secondary metabolites in plant in vitro culture. In this research, C. avellana cell suspension culture (CSC) was exposed to cell extract (CE) and culture filtrate (CF) derived from Camarosporomyces flavigenus, either individually or combined treatment, in mid and late log phase. There is no report on the use of whole fungal elicitors (the combined treatment of CE and CF) for the elicitation of secondary metabolite biosynthesis in plant in vitro culture. The combined treatment of CE and CF significantly led to more paclitaxel biosynthesis and secretion than the individual use of them. Also, multivariate statistical approaches including stepwise regression (SR), ordinary least squares regression (OLSR), principal component regression (PCR) and partial least squares regression (PLSR) were used to model and predict paclitaxel biosynthesis and secretion. Based on value account for (VAF), root mean square error (RMSE), coefficient of determination (R2), mean absolute percentage error (MAPE) and relative percent difference (RPD) can be concluded that mentioned regression models effectively worked only for modeling and predicting extracellular paclitaxel portion in C. avellana cell culture.

Impact of Soil Rhizobacteria Inoculation and Leaf-Chewing Insect Herbivory on Mentha piperita Leaf Secondary Metabolites.

Secondary metabolites commonly play important physiological roles in plants and can be modified quantitatively and qualitatively by exposure to biotic and abiotic interactions. Plant growth promoting rhizobacteria (PGPR) and herbivory induce systemic resistance. In the present study, we analyzed the induction of secondary metabolites in peppermint plants in response to chewing insect herbivory on PGPR-inoculated Mentha piperita plants. The secondary metabolites of M. piperita plants were increased when plants were inoculated with PGPR and also exposed to caterpillar herbivory. It was found that the total essential oil yield in inoculated plants with insect damage was ~2.6-fold higher than in controls. The yield was similar to that of plants either damaged by insects or inoculated, indicating that there was no synergism. The same trend was observed for phenolic compounds. In contrast, VOC emissions were significantly higher in plants infested by insects, independent of whether they were inoculated. Insect damaged plants had 5.5 times higher monoterpene emissions than control plants, and ~ 2-fold higher emissions than on PGPR-inoculated plants without insects. To gain a better understanding of how herbivory on PGPR-inoculated plants can cause an increase in secondary metabolites of peppermint, we examined changes in plant defense hormones in inoculated plants after herbivory. We found that the combination of both treatments increased the endogenous jasmonic and salicylic acid levels to the same extent as in plants only inoculated or only insect-damaged. Because different interactions can alter the phytochemistry of plants such as M. piperita, this topic is both ecologically and economically relevant.

Beneficial Effects of Endophytic Fungi from the Anoectochilus and Ludisia Species on the Growth and Secondary Metabolism of Anoectochilus roxburghii.

Endophytic fungi possess favorable effects on their host plants, including disease-resistance improvement, secondary metabolite induction, and growth promotion. It is therefore a promising and sustainable strategy to utilize endophytic fungi for the quality improvement of medicinal herbs or important crops. In our study, a collection of 277 strains of endophytic fungi were isolated from Anoectochilus and Ludisia orchids. Two strains J162 and J211 can be symbiotically cocultured with the tissue culture seedlings of Anoectochilus roxburghii, a popular medicinal and edible plant in southern China. Both strains can significantly enhance the biomass of A. roxburghii and induce the biosynthesis and accumulation of its active ingredients, including flavonoids, kinsenoside, and polysaccharides. J162 and J211 were further identified as Chaetomium globosum and Colletotrichum gloeosporioides based on multilocus phylogenetic analysis. Immunocytochemical staining indicated that J162 and J211 mainly colonized the intercellular gap of xylem parenchyma cells of A. roxburghii roots without obvious harm. In addition, quantitative real-time polymerase chain reaction showed that the expression of three growth-related genes, namely, uracil phosphoribosyl transferase, amino acid transmembrane transporter, and maturase K, were significantly altered in A. roxburghii plants when treated with J162 and J211. In conclusion, the two strains are highly beneficial microbial resources for the growth and accumulation of active ingredients of A. roxburghii in agricultural cultivation.

Variation in Below-to Aboveground Systemic Induction of Glucosinolates Mediates Plant Fitness Consequences under Herbivore Attack.

Plants defend themselves against herbivore attack by constitutively producing toxic secondary metabolites, as well as by inducing them in response to herbivore feeding. Induction of secondary metabolites can cross plant tissue boundaries, such as from root to shoot. However, whether the potential for plants to systemically induce secondary metabolites from roots to shoots shows genetic variability, and thus, potentially, is under selection conferring fitness benefits to the plants is an open question. To address this question, we induced 26 maternal plant families of the wild species Cardamine hirsuta belowground (BG) using the wound-mimicking phytohormone jasmonic acid (JA). We measured resistance against a generalist (Spodoptera littoralis) and a specialist (Pieris brassicae) herbivore species, as well as the production of glucosinolates (GSLs) in plants. We showed that BG induction increased AG resistance against the generalist but not against the specialist, and found substantial plant family-level variation for resistance and GSL induction. We further found that the systemic induction of several GSLs tempered the negative effects of herbivory on total seed set production. Using a widespread natural system, we thus confirm that BG to AG induction has a strong genetic component, and can be under positive selection by increasing plant fitness. We suggest that natural variation in systemic induction is in part dictated by allocation trade-offs between constitutive and inducible GSL production, as well as natural variation in AG and BG herbivore attack in nature.

Effect of hydropriming on Trigonella foenum callus growth, biochemical traits and phytochemical components under PEG treatment

The induction of secondary metabolites under osmotic stress is well documented. However, cell death is probably due to osmotic stress. This work tries to study the synergetic effect of hydropriming and polyethylene glycol (PEG) on enhancing the secondary metabolites production in fenugreek callus cultures without facing cell death. PEG initiates the stress and the hydropriming increase the plant cell response against the stress. Fenugreek calli were initiated from hypocotyl of two groups of seeds, the first was hydroprimed overnight before germination, the second remained dry. Three months old calli of the two groups were subcultured on media containing two different concentration of PEG (5, 10%). The calli growth, biochemical analysis, secondary metabolism keys, and secondary metabolites were determined after 4 weeks. PE induced oxidative stress, which increased the membrane lipid peroxidation and decreased cell viability and growth. Hydropriming enhanced the activity of antioxidant enzymes, regulating the reactive oxygen species level, accumulating the osmolytes and secondary products. Therefore the primed callus can tolerate the osmotic stress initiated with PEG. Consequently, cell biomass increased and not affected by PEG treatment. On the other hand, the calli from non-primed seeds have a significant decrease in fresh weight, and dry weight under the higher PEG treatment. The hydropriming protected the growth of the cells under PEG treatment with a high content of secondary metabolites and high antioxidant machinery. The synergetic effect of hydropriming and PEG can be used as a simple and low-cost way to produce valuable compounds in commercial industrial bioreactors. The synergetic effect of hydropriming and PEG enhances the secondary metabolites production in fenugreek callus. PEG initiates the stress and the hydropriming improves the plant cell response against the stress.

Response mechanism of hypocrellin colorants biosynthesis by Shiraia bambusicola to elicitor PB90

The valuable medicine Shiraia bambusicola P. Henn. and its major active substance hypocrellin exert unique curative effects on skin diseases, diabetes, and cancers. The wild S. bambusicola is endangered due to its harsh breeding conditions and long growth cycle. It is one of the effective ways to utilize the resources sustainably to produce hypocrellin by fermentation of S. bambusicola. PB90 is a protein elicitor isolated from Phytophthora boehmeriae to induce the useful metabolites production in fungi. In this work, PB90 was selected to promote the synthesis hypocrellin by S. bambusicola. To evaluate the effect of PB90 on S. bambusicola, it was found that the induced cells showed decreased biomass, increased cell wall permeability, rapid induction of secondary metabolites, and significant increase of some enzyme activities, which confirmed a strong activation of phenylalanine/flavonoid pathways. Studies on signal molecules and gene expression level in S. bambusicola treated with PB90 have found that hydrogen peroxide (H2O2) and nitric oxide (NO) are necessary signal molecules involved in the synthesis of hypocrellin in elicited cells, and increased their signal levels through mutual reaction. We have showed for the first time, the response mechanism of hypocrellin biosynthesis from S. bambusicola to PB90, which may be not only establish a theoretical foundation for the application of PB90 to the mass production of S. bambusicola, but can also motivate further research on the application of PB90 to the conservation and sustainable utilization of other medical fungi.

Rain downpours affect survival and development of insect herbivores: the specter of climate change?

Changes in the frequency, duration, and intensity of rainfall events are among the abiotic effects predicted under anthropogenic global warming. Heavy downpours may profoundly affect the development and survival of small organisms such as insects. Here, we examined direct (physically on the insects) and indirect (plant‐mediated) effects of simulated downpours on the performance of caterpillars of two lepidopteran herbivores (Plutella xylostella and Pieris brassicae) feeding on black mustard (Brassica nigra) plants. Host plants were exposed to different rainfall regimes both before and while caterpillars were feeding on the plants in an attempt to separate direct and indirect (plant‐mediated) effects of rainfall on insect survival and development. In two independent experiments, downpours were simulated as a single long (20 min) or as three short (5 min) daily events. Downpours had a strong negative direct effect on the survival of P. xylostella, but not on that of P. brassicae. Direct effects of downpours consistently increased development time of both herbivore species, whereas effects on body mass depended on herbivore species and downpour frequency. Caterpillar disturbance by rain and recorded microclimatic cooling by 5°C may explain extended immature development. Indirect, plant‐mediated effects of downpours on the herbivores were generally small, despite the fact that sugar concentrations were reduced and herbivore induction of secondary metabolites (glucosinolates) was enhanced in plants exposed to rain. Changes in the frequency of precipitation events due to climate change may impact the survival and development of insect herbivores differentially. Broader effects of downpours on insects and other arthropods up the food chain could seriously impair and disrupt trophic interactions, ultimately destabilizing communities.

Nutrient limitation as a tool for the induction of secondary metabolites with antioxidant activity in basil cultivars

Sweet basil (Ocimum spp.) is an important source of secondary metabolites with a significant diversity of polyphenolic compounds. In order to investigate possibilities of induced synthesis of secondary metabolites under conditions of limited nutrition, four basil cultivars (‘Small leaved’, ‘Genovese’, ‘Dark Opal’ and ‘Lemon basil’) were exposed to different levels of mineral nutrition (high, medium and low) with two forms of nitrogen (nitrate alone or in combination with ammonium) and under controlled conditions. Nutrient limitation effects have been assessed on lipid peroxidation, the activity of phenylalanine ammonium lyase (PAL), total phenolic content, flavonoid concentration, and total antioxidant activity together with LC-DAD-MS/MS analysis of main phenolic acids in different plant parts. After one month of prolonged nutrient limitation results clearly indicate induced synthesis of assessed metabolites, together with lower lipid peroxidation, higher PAL activity, and prominent antioxidant activity. The results are also cultivar and nutrient specific. The highest content of phenolic compounds (particularly caffeic acid – 1.45 mg g−1 DW) and the highest antioxidant activity (IC50 = 22.36 μg ml−1) was in extracts from ‘Small leaved’ basil roots, whereas the highest concentration of rosmarinic acid (61.2 mg g−1 DW) was in extracts from ‘Genovese’ basil roots, both under the condition of nutrient limitation. This study provided a novel approach for the higher metabolite production with uniformity of cultivation conditions and lower content of mineral nutrition applied and pointed out to basil roots as a viable source of metabolites of interests.

Induction of Secondary Metabolites from the Marine-Derived Fungus Aspergillus versicolor through Co-cultivation with Bacillus subtilis.

A new cyclic pentapeptide, cotteslosin C (1: ), a new aflaquinolone, 22-epi-aflaquinolone B (3: ), and two new anthraquinones (9: and 10: ), along with thirty known compounds (2, 4: - 8, 11: - 34: ) were isolated from a co-culture of the sponge-associated fungus Aspergillus versicolor with Bacillus subtilis. The new metabolites were only detected in the co-culture extract, but not when the fungus was grown under axenic conditions. Furthermore, the co-culture extract exhibited an enhanced accumulation of the known constituents versicolorin B (14: ), averufin (16: ), and sterigmatocyctin (19: ) by factors of 1.5, 2.0, and 4.7, respectively, compared to the axenic fungal culture. The structures of the isolated compounds were elucidated on the basis of 1D and 2D NMR spectra and mass spectrometry as well as by comparison with literature data. The absolute configuration of compounds 3, 9: , and 10: was determined by ECD (electronic circular dichroism) analysis aided by TDDFT-ECD (time-dependent density functional theory electronic circular dichroism) calculations. Compounds 15, 18: - 21: , and 26: exhibited strong to moderate cytotoxic activity against the mouse lymphoma cell line L5178Y, with IC50 values ranging from 2.0 to 21.2 µM, while compounds 14, 16, 31, 32: , and 33: displayed moderate inhibitory activities against several gram-positive bacteria, with MIC values ranging from 12.5 to 50 µM.

Microbial secondary metabolite induction of abnormal appressoria formation mediates control of rice blast disease caused by Magnaporthe oryzae

AbstractOkinawa, the only subtropical area in Japan with numerous island ecosystems, is expected to have diverse microbial resources. Recently, we reported the construction of a culture filtrate library with microbes originally isolated from soils in Okinawa, including the Yaeyama Archipelago, and validated its phylogenetic diversity. In the present study, we investigated the inhibitory effect of the cell extract (CE) from microbial isolate 3–45 against Magnaporthe oryzae in rice (Oryza sativa). Abnormal appressorium formation by M. oryzae was induced in the presence of the CE from isolate 3–45. Additionally, melanization of appressoria was inhibited in the presence of CE from isolate 3–45. Sequence analysis of the 16S rDNA region of isolate 3–45 indicated that it shared similarities with Streptomyces erythrochromogenes. When rice leaves were inoculated with M. oryzae in the presence of CE from isolate 3–45, blast lesion formation was inhibited compared to leaves treated with M. oryzae in the absence of CE from isolate 3–45. In addition, M. oryzae infective activity was significantly inhibited in rice leaf sheaths treated with CE from isolate 3–45. Furthermore, abnormal appressorium formation was observed in the presence of heat‐treated CE from isolate 3–45. These results suggest that CE from isolate 3–45 can protect rice from blast disease caused by M. oryzae. Further studies are required to identify the active compounds present in 3–45‐CE and to clarify its mechanism of inhibition in full detail. The present study on isolate 3–45 might contribute to the development of a new fungicide for controlling rice blast disease caused by M. oryzae.

Gongronella sp. w5 elevates Coprinopsis cinerea laccase production by carbon source syntrophism and secondary metabolite induction.

When sucrose was used as the carbon source, the Basidiomycete Coprinopsis cinerea showed poor growth and low laccase activity in pure culture, butgreatly enhanced the level of laccase activity (>1800 U/L) during coculture with the Mucoromycete Gongronella sp. w5. As a result, the mechanism of laccase overproduction in coculture was investigated by starting from clarifying the function of sucrose. Results demonstrated that Gongronella sp. w5 in the coculture system hydrolyzed sucrose to glucose and fructoseby an intracellular invertase. Fructose rather than glucose was supplied byGongronella sp. w5 as the readily available carbon source for C. cinerea, and contributed to an alteration of its growth behavior and a basal laccase secretion of 110.6 ± 3.3U/L. On the other hand, separating Gongronella sp. w5 of C. cinerea by transfer into dialysis tubes yielded the same levelof laccase activity as without separation, indicating that enhanced laccase production probably resulted from the metabolites in the fermentation broth. Further investigation showed that the ethyl acetate-extracted metabolites generated by Gongronella sp. w5 induced C. cinerea laccase production. One of the laccase-inducing compounds namely p-hydroxybenzoic acid (HBA) was purified and identified from the extract. When using HBA as the inducer and fructose as the carbon source in monoculture, C. cinerea observed similar high laccase activity to that in coculture, and zymograms revealed the same expression of laccase Lcc9 as the main and Lcc1 and Lcc5 as the minor enzymes. Overall, our experiments verified that Gongronella sp. w5 elevates Coprinopsis cinerea laccase production by carbon source syntrophism and secondary metabolite induction.

Interactive effects of drought severity and simulated herbivory on tea (Camellia sinensis) volatile and non-volatile metabolites

Plants often experience multiple sources of stress simultaneously, yet little is known about interactive effects of multiple stressors on plant metabolic responses. Plants are well known to respond to both drought and insect herbivory through the induced production of secondary metabolites. However, severe drought stress limits photosynthesis and may therefore inhibit the production of induced secondary metabolites in response to herbivory due to carbon limitation. On the other hand, drought-stressed plants may be primed to respond more strongly to herbivory due to hormonal crosstalk or redundancy of metabolites that are produced in response to drought and herbivory. We tested the interactive effects of drought and simulated herbivory in tea plants (Camellia sinensis (L.) Kuntze var. sinensis) grown in the field under varying rainfall interception treatments and then exposed to an exogenous methyl jasmonate (MeJA) treatment.We show that severe drought generally inhibits the induction of secondary metabolites by exogenous MeJA (simulated herbivory). However, a few volatile metabolites, including methyl salicylate, are more strongly induced by MeJA in severely drought-stressed plants compared to moderately stressed plants, possibly due to priming by drought stress. Our approach of using multiple levels of drought stress and a targeted/untargeted approach to measuring volatile metabolites was essential to discovering these patterns of induction. In addition to having implications for plant-herbivore interactions in the presence of abiotic stress, these results have important implications for tea quality.

Differential Impact of Herbivores from Three Feeding Guilds on Systemic Secondary Metabolite Induction, Phytohormone Levels and Plant-Mediated Herbivore Interactions.

Phytochemical defense responses of plants are often herbivore-specific and can be affected by a herbivore's feeding mode. However, comprehensive studies documenting the impact of multiple herbivores from different feeding guilds on induced phytochemical responses in distal leaves and its consequences for plant-mediated herbivore interactions are limited and findings are inconsistent. We investigated how herbivory by leaf-chewing caterpillars, cell-content feeding spider mites and phloem-feeding aphids and whiteflies affect secondary metabolomes and phytohormone levels in youngest, non-damaged cotton leaves (distal leaves). Furthermore, bioassays with caterpillars were conducted to assess their performance on distal leaves of plants infested with different herbivores. Caterpillars, and to a lesser degree spider mites, led to a systemic induction of terpenoids with negative consequences for caterpillar performance in the bioassays. Both herbivores reduced levels of various nutrients and potentially antioxidative compounds. Caterpillar damage increased levels of jasmonoyl-L-isoleucine and abscisic acid (ABA), whereas spider mite infestation had no effect on phytohormone levels. Aphid and whitefly infestation did not systemically affect secondary metabolites. Aphids decreased salicylic acid levels while whitefly-infested plants contained increased ABA levels. Neither aphid nor whitefly infestation affected caterpillar performance. In general, feeding mode of a herbivore can affect systemically induced changes in phytochemistry and plant-mediated indirect interactions even though the two phloem-feeding herbivores triggered different phytohormonal responses. The observed reduction of nutrients and potentially antioxidative compounds upon caterpillar and spider mite herbivory underlines the importance of further elucidating the role of resource sequestration as a potential systemic defensive response following herbivory by chewers and cell-content feeding herbivores.

Spodoptera litura-mediated chemical defense is differentially modulated in older and younger systemic leaves of Solanum lycopersicum.

Metabolite profiling, biochemical assays, and transcript analysis revealed differential modulation of specific induced defense responses in local, older, and younger systemic leaves in Solanum lycopersicum upon Spodoptera litura herbivory. Plants reconfigure their metabolome upon herbivory to induce production of defense metabolites involved in both direct and indirect defenses against insect herbivores. Herbivory mediated leaf-to-leaf systemic induction pattern of primary and non-volatile secondary metabolites is not well studied in tomato. Here, we show that, in cultivated tomato Solanum lycopersicum herbivory by generalist insect, Spodoptera litura results in differential alteration of primary metabolites, majorly sugars and amino acids and specific secondary metabolites in local, younger, and older systemic leaves. Cluster analysis of 55 metabolites identified by GC-MS showed correlation between local and younger systemic leaves. Re-allocation of primary metabolites like glucose and amino acids from the local to systemic leaf was observed. Secondary metabolites chlorogenic acid, caffeic acid, and catechin were significantly induced during herbivory in systemic leaves. Among specific secondary metabolites, chlorogenic acid and catechin significantly inhibits S. litura larval growth in all stages. Local leaf exhibited increased lignin accumulation upon herbivory. Differential alteration of induced defense responses like reactive oxygen species, polyphenol oxidase activity, proteinase inhibitor, cell wall metabolites, and lignin accumulation was observed in systemic leaves. The metabolite alteration also resulted in increased defense in systemic leaves. Thus, comparative analysis of metabolites in local and systemic leaves of tomato revealed a constant re-allocation of primary metabolites to systemic leaves and differential induction of secondary metabolites and induced defenses upon herbivory.