Role of castor plant phenolics on performance of its two herbivores and their impact on egg parasitoid behaviour

Plants are reported to reconfigure their metabolism and generate secondary metabolites as a defence response towards herbivore attack. In this study we aimed to evaluate the anti-nutritive and defensive properties of phenolic compounds that were enhanced in Castor, Ricinus communis L. plant due to herbivore damage. Through HPLC studies it was observed that damage caused by two pests, Achaea janata L. and Spodoptera litura F. on the castor plant resulted in quantitative enhancement of syringic, coumaric, cinnamic and vanillic acids. These phenolic compounds showed considerable impact on insect’s feeding and their toxic nature towards the herbivores was determined by estimating three detoxification mid-gut enzymes, glutathione-s-transferase, carboxyl esterase and β-glucosidase. In the ovipositional and orientation bioassays with the egg parasitoid Trichogramma chilonis Ishii, syringic and coumaric acids had shown good kairomonal activity, thus defining a new role of these chemicals in indirect plant defence. Thus, this study demonstrates a quantitative association between plant phenolic accumulation and the elevated reproductive performance of the herbivore natural enemies, by illustrating the role of plant phenolics in both the direct and indirect induced plant defences.     

Temperature Impacts the Development and Survival of Common Cutworm (Spodoptera litura): Simulation and Visualization of Potential Population Growth in India under Warmer Temperatures through Life Cycle Modelling and Spatial Mapping

The common cutworm, Spodoptera litura, has become a major pest of soybean (Glycine max) throughout its Indian range. With a changing climate, there is the potential for this insect to become an increasingly severe pest in certain regions due to increased habitat suitability. To examine this possibility, we developed temperature-based phenology model for S. litura, by constructing thermal reaction norms for cohorts of single life stages, at both constant and fluctuating temperatures within the ecologically relevant range (15–38°C) for its development. Life table parameters were estimated stochastically using cohort updating and rate summation approach. The model was implemented in the geographic information system to examine the potential future pest status of S. litura using temperature change projections from SRES A₁B climate change scenario for the year 2050. The changes were visualized by means of three spatial indices demonstrating the risks for establishment, number of generations per year and pest abundance according to the temperature conditions. The results revealed that the development rate as a function of temperature increased linearly for all the immature stages of S. litura until approximately 34–36°C, after which it became non-linear. The extreme temperature of 38°C was found lethal to larval and pupal stages of S. litura wherein no development to the next stage occurred. Females could lay no eggs at the extreme low (15°C) and high (> 35°C) test temperatures, demonstrating the importance of optimum temperature in determining the suitability of climate for the mating and reproduction in S. litura. The risk mapping predicts that due to temperature increase under future climate change, much of the soybean areas in Indian states like Madhya Pradesh, Maharashtra and Rajasthan, will become suitable for S. litura establishment and increased pest activity, indicating the expansion of the suitable and favourable areas over time. This has serious implication in terms of soybean production since these areas produce approximately 95% of the total soybeans in India. As the present model results are based on temperature only, and the effects of other abiotic and biotic factors determining the pest population dynamics were excluded, it presents only the potential population growth parameters for S. litura. However, if combined with the field observations, the model results could certainly contribute to gaining insight into the field dynamics of S. litura.     

6种植物次生物质对斜纹夜蛾解毒酶活性的影响

草食性昆虫取食植物时遇到宿主植物中大量次生物质的化学防御,研究昆虫适应植物毒素的反防御策略具有重要的科学意义。分别添加0.01%肉桂酸、0.01%水杨酸、0.01%花椒毒素、0.02%槲皮素、0.05%黄酮和0.1%香豆素等6种植物次生物质的人工饲料饲养斜纹夜蛾(Spodoptera litura)五龄幼虫48 h后,测定斜纹夜蛾幼虫中肠和脂肪体中谷胱甘肽S-转移酶(GSTs)、羧酸酯酶(CarE)、P450的酶含量及头部乙酰胆碱酯酶(AChE)的活性,利用半定量RT-PCR检测中肠和脂肪体中CYP4M14和CYP4S9的基因表达水平。结果表明:取食肉桂酸和香豆素后,斜纹夜蛾中肠中CarE的酶活性分别提高了1.67和1.37倍,取食6种次生物质均能显著提高斜纹夜蛾脂肪体中GSTs酶活性。取食肉桂酸和香豆素48 h后,脂肪体中P450酶含量比对照增加2.93和14.50倍。取食肉桂酸、花椒毒素、槲皮素和香豆素后,斜纹夜蛾头部AchE酶活性与对照相比提高了1.53、1.80、2.36和1.56倍。6种次生物质均可诱导脂肪体中CYP4M14基因表达,槲皮素、肉桂酸和香豆素强烈诱导CYP4S9在脂肪体中表达。表明,斜纹夜蛾具有利用植物次生物质诱导其解毒酶的能力,进而提高其对毒素的抗性。     

Foraging and growth responses of cotton armyworm Spodoptera litura to the biophysical characteristics of five cotton varieties

This study investigated the morphological and biochemical characteristics of the CB1, CB3, CB5, CB8 and CB12 cotton varieties and evaluated their effects on third instar larval movement, and body weight of the cotton armyworm Spodoptera litura at different developmental stages. The cotton varieties differed in their plant architecture, branching, stem color and hairiness, leaf color and hairiness, leaf trichome density, flower color, numbers of leaves and bolls per plant, concentrations of protein and starch, and boll length, width and weight. The CB1 and CB3 varieties possessed significantly higher trichome densities, while CB8 produced larger and heavier bolls. Boll bearing was found to be highest in CB1 and lowest in CB8. Biochemical analyses indicated the highest percentage of protein in CB5, and of starch in CB8; concentrations of both were lowest in CB12. Cotton varieties did not affect larval foraging, but their abundance on leaflet, mature and square differed significantly. Analysis of the growth response parameters of S. litura as a result of feeding on the tested varieties revealed that larval instars, pupae and adult moths attained the highest body weight on CB8, followed by CB5, and the lowest weight on CB12. Collectively, the results of this study show that the CB5 and CB8 varieties are favorable host‐plants for cotton armyworms; therefore, these varieties are the least suitable for cultivation.     

Methyl jasmonate induced responses in four plant species and its effect on Spodoptera litura Fab. performance

Defensive proteins, such as polyphenol oxidase (PPO) and trypsin inhibitor (TI), are induced by herbivore wounding and exogenous methyl jasmonate application in various plant species. This study was conducted to measure induction of PPO and TI in radish, sweet pepper, tomato, and water spinach plants following herbivore wounding (I), methyl jasmonate application (M), and a combination of the two treatments (M + I). The effect of induced responses was also examined against third instar Spodoptera litura Fab. PPO activity was induced in radish by treatment I only; in sweet pepper, by treatments I and M; in tomato, by treatments I, M, and M + I; and in water spinach, by treatments M and M + I. The activity of TI was enhanced 1.2–1.4-fold in radish, sweet pepper, and tomato by M and M + I treatments, whereas in water spinach, it was enhanced 1.2-fold by all 3 treatments. The relative growth rate (RGR) of S. litura was reduced by 53% on radish plants following M treatment only. It was reduced by 37% and 42% on sweet paper plants following M and M + I treatment, respectively. RGR was significantly reduced on test tomato plants following I, M, and M + I treatments. The RGR of S. litura was unaffected on water spinach plants following any treatment. Collectively, the results of this study indicated that induction of plant defensive proteins in response to S. litura feeding or exogenous methyl jasmonate application varied among plant species, which further affected the induced plant resistance to the caterpillars.     

Impact of Plant Phenolics as Semiochemicals on the Performance of <Emphasis Type="Italic">Trichogramma chilonis</Emphasis> Ishii

Phenolic compounds play a major role in the plant defense mechanisms and often offer protection from the feeding herbivore. They also constitute a major chemical component of many agriculturally important crops. We examined the effects of 23 common phenolic acids on the orientation and ovipositional behavior of the egg parasitoid, Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae). The study was conducted in order to investigate the function of these compounds in the plant indirect defense. Parasitoids attractions towards the phenolics that are volatile in nature were observed by using culture tube bioassays. In addition in the Y- tube olfactometer experiments, T. chilonis were shown to be attracted towards the treatments of syringic, pyrocatechol, coumaric and quercetin at minimum dose of 10 μg and genistein, chlorogenic, vanillic, chlorobenzoic, sinapic, ellagic, protocatechuic, keampferol, tannic, caffeic, and luteolin at 30 μg and ferulic, epicatechin and gallic acid at 50 μg doses. Further experiments to examine the effect of phenolic compounds on parasitization by T. chilonis females were carried out using petri dish and artificial plant models. Among the tested compounds, syringic acid and quercetin recorded the highest percentage parasitization followed by coumaric acid and pyrocatechol. These results might imply that parasitoid attractant phenolic compounds when induced in engineered plants can further be used as cues by the egg parasitoids with potential application in biocontrol strategies.     

Phenolic acid and DNA contents of micropropagated Eryngium planum L.

A protocol for in vitro production of genetically uniform populations of the medicinal plant Eryngium planum, rich in selected phenolic acids, has been established. Shoot-tips were collected from axenic seedlings and grown on a Murashige and Skoog basal medium supplemented with 6-Benzyladenine (BA) and Indole-3-acetic acid (IAA). The highest shoot proliferation efficiency (17 shoots per explant) was obtained when 1.0 mg L^?1 BA and 0.1 mg L^?1 were added. Proliferating shoots were rooted and transferred to soil (89 % frequency of survival). Flow cytometric analysis of intact (field-grown) and microrpropagated plants revealed that all plants were uniform in genome size and had similar DNA contents. Thin-layer chromatography (TLC) analysis indicated that multiple shoots and roots from in vitro-derived plants produced high amounts of phenolic acids, primarily of rosmarinic acid (RA). Levels of phenolic acids in in vitro-derived plants were similar to those of intact plants. Furthermore, high-performance liquid chromatography revealed that root cultures in liquid medium accumulated substantial levels of RA. Thus, rapid establishment of in vitro-grown organ cultures of E. planum can also serve as reliable sources for bioactive compounds.     

Inducing gene expression of cardiac antioxidant enzymes by dietary phenolic acids in rats

An increase in oxidative stress is suggested to be intimately involved in the pathogenesis of heart failure. Phenolic acids are widespread in plant foods; they contain important biological and pharmacological properties. This study evaluated the role of phenolic acids on the expression of antioxidant enzymes in the heart of male Sprague-Dawley rats. Gallic acid, ferulic acid and p-coumaric acid at a dosage of 100 mg kg(-1) body weight significantly increased the activities of cardiac superoxide dismutase, glutathione peroxidase (GPx) and catalase (CAT) as compared with control rats (P<.05). The changes in cardiac CuZnSOD, GPx and CAT mRNA levels induced by phenolic acids were similar to those noted in the enzyme activity levels. A significant (P<.05) increase in the GSH/GSSG ratio was observed in the heart of phenolic acid-treated rats. The heart homogenates obtained from rats that were administered phenolic acids displayed significant (P<.05) increases in capacity for oxygen radical absorbance compared with control rats. Immunoblot analysis revealed the increased cardiac total level of Nrf2 in phenolic acid-treated rats. Interestingly, phenolic acid-mediated antioxidant enzyme expression was accompanied by up-regulation of heme oxygenase-1. This study demonstrates that antioxidant enzymes in rat cardiac tissue can be significantly induced by phenolic acids following oral administration.     

Distribution of enzymes that catalyse reactions of glutathione with αβ-unsaturated compounds

1. A study of the distribution of glutathione S-alkenetransferases in the livers of vertebrate species suggests that different enzymes may catalyse reactions of GSH with (i) trans-benzylideneacetone, (ii) 2,3-dimethyl-4(2-methylenebutyryl)phenoxyacetic acid, (iii) cinnamonitrile, (iv) o-chlorobenzylidenemalononitrile, (v) methyl vinyl sulphone, and (vi) 3-(β-nitrovinyl)indole. 2. Glutathione S-alkenetransferase activity was generally greatest in rat liver, but the enzyme in hamster liver was more active towards o-chlorobenzylidenemalononitrile, and the enzyme in rabbit, hamster, guinea-pig and mouse livers was more active towards methyl vinyl sulphone. 3. Results from studies of the distribution of activities in rat liver and rat kidney, heat inactivation of rat liver supernatants, and (NH₄)₂SO₄ fractionation and acid-precipitation experiments, differentiated further between some of the enzymes concerned with substrates (i)–(vi). 4. The infrequent detection of mercapturic acids in vivo is discussed.     

Antioxidant and phenolic acid profiles of tissue cultured and acclimatized Merwilla plumbea plantlets in relation to the applied cytokinins

Merwilla plumbea (Lindl.) Speta is an important medicinal plant widely used in traditional medicine. We evaluated the effect of five cytokinins [benzyladenine (BA), 2-isopentenyladenine (2iP), meta-topolin (mT), meta-topolin riboside (mTR), and meta-methoxy-9-tetrahydropyran-2-yl-topolin (MemTTHP)] on the level of phenolic acids and antioxidant activity of M. plumbea during the tissue culture and acclimatization stages. Two cytokinins (mT and mTR) significantly improved the antioxidant activity of tissue culture plantlets while the control plantlets were better after acclimatization. Using UPLC–MS/MS, the levels of hydroxybenzoic and hydroxycinnamic acid derivatives (phenolic acids) varied significantly during tissue culture and acclimatization, depending on the cytokinin and plant part analyzed. Vanillic acid (24.9 μg g⁻¹) detected in underground parts of tissue culture plants supplemented with BA was the most abundant phenolic acid detected. The current findings indicate that the phytochemicals together with the bioactivity during in vitro propagation of M. plumbea is influenced by the cytokinin type used and the stage of plant material collection.     

The effect of some phenolic compounds on the activity of 6-phosphogluconate dehydrogenase from tobacco tissue cultures

Anodic polyacrylamide gel electrophoresis of extracts of cultures of tobacco tissue Nicotiana tabacum W-38 revealed the presence of two 6-phosphogluconate dehydrogenases (6PGD). The slow and the fast anodic migrating zones were designated I and II, respectively. After purification, enzymes from both zones exhibited no major differences in their affinity towards 6-phosphogluconate (6PG) or NADP⁺, and were found to have approximately the same pH optima and MWs (69 000–72 000). The coumarins scopoletin and esculetin showed some inhibitory effect on each isozyme at 0.4 mM. Below 0.3 mM, however, esculetin stimulated the activity of zone I when lower amounts of 6PG (S_0.25) were used. The glucosylated compounds, scopolin and esculin, were much more inhibitory towards the 6PGDs than their respective aglycones. Ferulic, p-coumaric and caffeic acids seemed to have an inhibitory effect dependent on 6PG concentration. A larger inhibition was observed in each case at the lower 6PG levels used. Zone I activity appeared to be inhibited to a greater degree than zone II activity by 0.4 mM p-coumaric acid with low 6PG. Of the phenolic compounds tested, chlorogenic acid was most effective, completely inhibiting the enzyme activity at 0.4 mM. Of the non-phenolic compounds investigated, glucose 1,6-diphosphate inhibited both isoenzymes of 6PGD at lower 6PG concentrations. On the other hand, 2,3-diphosphoglycerate activated both isoenzymes up to 200% of their original activity.     

Expression in Escherichia coli of Native and Chimeric Phenolic Acid Decarboxylases with Modified Enzymatic Activities and Method for Screening Recombinant E. coli Strains Expressing These Enzymes

Four bacterial phenolic acid decarboxylases (PAD) from Lactobacillus plantarum, Pediococcus pentosaceus, Bacillus subtilis, and Bacillus pumilus were expressed in Escherichia coli, and their activities on p-coumaric, ferulic, and caffeic acids were compared. Although these four enzymes displayed 61% amino acid sequence identity, they exhibit different activities for ferulic and caffeic acid metabolism. To elucidate the domain(s) that determines these differences, chimeric PAD proteins were constructed and expressed in E. coli by exchanging their individual carboxy-terminal portions. Analysis of the chimeric enzyme activities suggests that the C-terminal region may be involved in determining PAD substrate specificity and catalytic capacity. In order to test phenolic acid toxicity, the levels of growth of recombinant E. coli displaying and not displaying PAD activity were compared on medium supplemented with different concentrations of phenolic acids and with differing pHs. Though these acids already have a slight inhibitory effect on E. coli, vinyl phenol derivatives, created during decarboxylation of phenolic acids, were much more inhibitory to the E. coli control strain. To take advantage of this property, a solid medium with the appropriate pH and phenolic acid concentration was developed; in this medium the recombinant E. coli strains expressing PAD activity form colonies approximately five times smaller than those formed by strains devoid of PAD activity.     

Herbivore- and Elicitor- Induced Resistance in Groundnut to Asian armyworm,Spodoptera litura (Fab.) (Lepidoptera: Noctuidae)

Induced defense was studied in three groundnut genotypes ICGV 86699 (resistant), NCAc 343 (resistant) and TMV 2 (susceptible) in response to Spodoptera litura infestation and jasmonic acid (JA) application. The activity of the oxidative enzymes [peroxidase (POD) and polyphenol oxidase (PPO)] and the amounts other host plant defense components [total phenols, hydrogen peroxide (H2O2), malondialdehyde (MDA), and protein content] were recorded at 24, 48, 72 and 96 h in JA pretreated (one day before) plants and infested with S. litura, and JA application and simultaneous infestation with S. litura to understand the defense response of groundnut genotypes against S. litura damage. Data on plant damage, larval survival and larval weights were also recorded. There was a rapid increase in the activities of POD and PPO and in the quantities of total phenols, H2O2, MDA and protein content in the JA pretreated + S. litura infested plants. All the three genotypes showed quick response to JA application and S. litura infestation by increasing the defensive compounds. Among all the genotypes, higher induction was recorded in ICGV 86699 in most of the parameters. Reduced plant damage, low larval survival and larval weights were observed in JA pretreated plants. It suggests that pretreatment with elicitors, such as JA could provide more opportunity for plant defense against herbivores.     

Cloning and Functional Characterization of SAD Genes in Potato

Stearoyl-acyl carrier protein desaturase (SAD), locating in the plastid stroma, is an important fatty acid biosynthetic enzyme in higher plants. SAD catalyzes desaturation of stearoyl-ACP to oleyl-ACP and plays a key role in determining the homeostasis between saturated fatty acids and unsaturated fatty acids, which is an important player in cold acclimation in plants. Here, four new full-length cDNA of SADs (ScoSAD, SaSAD, ScaSAD and StSAD) were cloned from four Solanum species, Solanum commersonii, S. acaule, S. cardiophyllum and S. tuberosum, respectively. The ORF of the four SADs were 1182 bp in length, encoding 393 amino acids. A sequence alignment indicated 13 amino acids varied among the SADs of three wild species. Further analysis showed that the freezing tolerance and cold acclimation capacity of S. commersonii are similar to S. acaule and their SAD amino acid sequences were identical but differed from that of S. cardiophyllum, which is sensitive to freezing. Furthermore, the sequence alignments between StSAD and ScoSAD indicated that only 7 different amino acids at residues were found in SAD of S. tuberosum (Zhongshu8) against the protein sequence of ScoSAD. A phylogenetic analysis showed the three wild potato species had the closest genetic relationship with the SAD of S. lycopersicum and Nicotiana tomentosiformis but not S. tuberosum. The SAD gene from S. commersonii (ScoSAD) was cloned into multiple sites of the pBI121 plant binary vector and transformed into the cultivated potato variety Zhongshu 8. A freeze tolerance analysis showed overexpression of the ScoSAD gene in transgenic plants significantly enhanced freeze tolerance in cv. Zhongshu 8 and increased their linoleic acid content, suggesting that linoleic acid likely plays a key role in improving freeze tolerance in potato plants. This study provided some new insights into how SAD regulates in the freezing tolerance and cold acclimation in potato.     

Changes in the composition of phenolic compounds and antioxidant properties of grapevine roots and leaves (Vitis vinifera L.) under continuous of long-term drought stress

Grapevine seedlings Vitis vinifera L. were grown in a greenhouse under optimum conditions (soil moisture ca 70 %) and under drought stress (soil moisture ca 30 %). Drought stress caused reduction in total phenolic compounds in grapevine leaves and roots, where were identified tree phenolic acids: caffeic acid, p-coumaric acid and ferulic acid. All acids found in leaves and roots occurred in the ester-bound form. Only caffeic acid in leaves appeared in the free and ester-bound form. Caffeic acid was present in the highest concentrations. The content of ferulic acid was the lowest in both tissues. The levels of all phenolic acids in leaves and roots decreased significantly under the drought stress. All the extracts from grapevine leaves and roots had antioxidative properties, but the antiradical activity of the extracts obtained from roots subjected to drought stress was lower to the control. The results of the analysis revealed that long-term drought stress caused a decrease in selected elements of secondary metabolism in such a different plant tissues that are the leaves and roots of the grapevine.     

Induction of phenolic acids and metals in Arachis hypogaea L. plants due to feeding of three lepidopteran pests

The feeding of lepidopteran pests, Amsacta albistriga W., Aproaerema modicella D. and Spilosoma obliqua W., caused feeding stress in the Arachis hypogaea L. plants. As a common defensive response, the plant exhibited variations in the primary and secondary metabolic contents. Groundnut plant antioxidative enzymes such as peroxidase, superoxide dismutase, polyphenol oxidase, catalase and phenyl ammonia lyase exhibited alterations to confer resistance against the pest. Phenolic compounds, namely coumaric acid, chlorogenic acid, resveratrol, epicatechin, ferulic acid and caffeic acid, showed active defensive role in groundnut plant against the pest feeding through their significant presence in Fourier transform infrared spectroscopy, high-performance liquid chromatography and gas chromatography studies. Changes in metal contents like iron, magnesium, zinc, potassium and calcium were also reported through atomic absorption studies, indicating their defensive role against the biotic stress caused on groundnut by the three lepidopteran pests. The present study can further assist in recognizing the importance of these specific phenolic acids and metals of groundnut in its pest management.