Does Salicylic Acid Act as a Signal in Cotton for Induced Resistance to Helicoverpa zea?

Our previous study indicated that insect herbivory on cotton induced resistance to the cotton bollworm (Helicoverpa zea). Here we examine the role of salicylic acid as a signal in cotton for the induced resistance. Abundant evidence has accumulated showing that salicylic acid plays a key role in coordinating the expression of systemic acquired resistance against phyto-pathogens. We report that herbivory results in significant increases in foliar salicylic acid and H₂O₂, a response frequently observed following pathogenesis. In other well-studied systems (e.g., tobacco), salicylic acid inhibits the enzymatic decomposition of H₂O₂ by catalase and ascorbate peroxidase, but in cotton, salicylic acid has no effect on these enzymes in vitro. Furthermore, while herbivory enhances foliar catalase and ascorbate peroxidase activities, the application of salicylic acid or methyl salicylate to cotton plants does not affect foliar resistance to H. zea. The possible role of salicylic acid as a signal for induced resistance is discussed in light of these findings.     

Examination of Different Tobacco (Nicotiana spp.) Types Under- and Overproducing Tobacco Anionic Peroxidase for Their Leaf Resistance to Helicoverpa zea

First-instar larvae of the false tobacco budworm (corn earworm, Helicoverpa zea) that fed on either intact plants, leaf disks from undamaged plants, or leaf disks from insect-damaged plants of Nicotiana sylvestris and N. tabacum Coker plants overproducing a tobacco anionic peroxidase generally caused significantly less damage than those caged with corresponding material from wild-type plants. In some cases mortality was significantly higher and weights significantly less for caterpillars feeding on leaf material from overproducing vs. wild-type plants. First-instar H. zea fed on the same type of leaf material from N. tabacum Xanthi underproducing tobacco anionic peroxidase generally caused significantly more damage than those fed leaf material from wild-type plants. However, first-instar H. zea fed on underexpressing leaf material from N. sylvestris did not cause significantly greater damage compared to wild-type material. In cases where peroxidase enzyme activity was determined, significantly higher mean peroxidase activity was seen in leaves of plant types that also had significantly less mean feeding ratings. This information suggests that peroxidase activity can contribute to leaf resistance to chewing insects. However, the context of the peroxidase (cooccurring substrates, additional inducible factors) can mediate the degree of influence seen by changes in individual peroxidase isozyme levels.     

Toxicity of Aflatoxin B1 to Helicoverpa zea and Bioactivation by Cytochrome P450 Monooxygenases

Infestation of corn (Zea mays) by corn earworm (Helicoverpa zea) predisposes the plant to infection by Aspergillus fungi and concomitant contamination with the carcinogenic mycotoxin aflatoxin B1 (AFB1). Although effects of ingesting AFB1 are well documented in livestock and humans, the effects on insects that naturally encounter this mycotoxin are not as well defined. Toxicity of AFB1 to different stages of H. zea (first, third, and fifth instars) was evaluated with artificial diets containing varying concentrations. Although not acutely toxic at low concentrations (1−20 ng/g), AFB1 had significant chronic effects, including protracted development, increased mortality, decreased pupation rate, and reduced pupal weight. Sensitivity varied with developmental stage; whereas intermediate concentrations (200 ng/g) caused complete mortality in first instars, this same concentration had no detectable adverse effects on larvae encountering AFB1 in fifth instar. Fifth instars consuming AFB1 at higher concentrations (1 μg/g), however, displayed morphological deformities at pupation. That cytochrome P450 monooxygenases (P450s) are involved in the bioactivation of aflatoxin in this species is evidenced by the effects of piperonyl butoxide (PBO), a known P450 inhibitor, on toxicity; whereas no fourth instars pupated in the presence of 1 μg/g AFB1 in the diet, the presence of 0.1% PBO increased the pupation rate to 71.7%. Pupation rates of both fourth and fifth instars on diets containing 1 μg/g AFB1 also increased significantly in the presence of PBO. Effects of phenobarbital, a P450 inducer, on AFB1 toxicity were less dramatic than those of PBO. Collectively, these findings indicate that, as in many other vertebrates and invertebrates, toxicity of AFB1 to H. zea results from P450-mediated metabolic bioactivation.An erratum to this article can be found at     

Induced resistance in soybean toHelicoverpa zea: Role of plant protein quality

Resistance in soybean toHelicoverpa zea is comprised of both constitutive and inducible factors. In this study, we investigated the induction of resistance byH. zea in both greenhouse and field studies. In a greenhouse experiment, fourth-instarH. zea growth rates were reduced by 39% after 24 hr feeding and by 27% after 48 hr when larvae fed on previously wounded V3 foliage (cv. Forrest) compared with undamaged foliage. In a field study, the weight gain by larvae was more than 52% greater when larvae fed for 72 hr on undamaged R2/R3 soybean plants (cv. Braxton) compared to those that fed on previously wounded plants. A significant component of the induced resistance is due to a decline in the nutritional quality of foliar protein following foliar damage byH. zea. Foliar protein was extracted from damaged and undamaged foliage and incorporated into artificial diets. Larval growth was reduced 26% after four days and 49% after seven days on diets containing protein from damaged plants compared to larvae feeding on foliar protein from undamaged plants. Chemical analyses of protein quality also indicated a decline in quality in damaged plants compared to unwounded plants. Increases in lipoxygenase activity (53%), lipid peroxidation products (20%), and trypsin inhibitor content (34%) were observed in protein from wounded plants. Moreover, a 5.9% loss in free amines and 19% loss in total thiols occurred in protein from wounded plants. Larval feeding causes a significant increase in foliar lipoxygenase activity that varied among genotypes. Lipoxygenase isozymes were measured at pH 5.5, pH 7.0, and pH 8.5 in V3 stage plants of Forrest, Hark, D75-1069, and PI 417061 genotypes. Lipoxygenase activity in each genotype was significantly increased after 72 hr of larval feeding at each pH level tested, with the exception of lipoxygenase isozymes at pH 5.5 in genotype PI 417061. Larval feeding on R2/R3 stage plants (field-grown cv. Braxton) for six days also increased foliar lipoxygenase activity.     

Roles of Oxalic and Malic Acids in Chickpea Trichome Exudate in Host-Plant Resistance to Helicoverpa armigera

Effects of malic acid and oxalic acid on oviposition of Helicoverpa armigera were investigated in a laboratory cage choice experiment. Malic acid stimulated oviposition at a concentration of 0.6 μmol/cm² but inhibited it at 3.4 μmol/cm². Oxalic acid showed neither stimulation nor inhibition of oviposition at 0.25–1.7 μmol/cm². Correlations between the amount of these acids in trichome exudate on leaf and pod surface and H. armigera populations and pod damage were investigated in a field experiment using 14 chickpea genotypes. Malic acid on the leaves stimulated oviposition during the vegetative and flowering stages, when its concentration was 0.1–0.7 μmol/cm². Later, during the podding stage there was no significant correlation between either egg density or pod damage and malic acid levels. However, there was a significant negative correlation between pod damage and oxalic acid levels. Oxalic acid, which had been reported to have an antibiotic effect on H. armigera larvae, has an important role in resistance to this pest in chickpea. The length of the podding period was also a factor influencing the extent of pod damage; a longer podding period resulted in prolonged exposure to H. armigera attack and more pod damage.     

Multiple Mechanisms Mediate Resistance to Sorafenib in Urothelial Cancer

Genetic and epigenetic changes in the mitogen activated protein kinase (MAPK) signaling render urothelial cancer a potential target for tyrosine kinase inhibitor (TKI) treatment. However, clinical trials of several TKIs failed to prove efficacy. In this context, we investigated changes in MAPK signaling activity, downstream apoptotic regulators and changes in cell cycle distribution in different urothelial cancer cell lines (UCCs) upon treatment with the multikinase inhibitor sorafenib. None of the classical sorafenib targets (vascular endothelial growth factor receptor 1/-receptor 2, VEGFR1/-R2; platelet-derived growth factor receptor α/-receptor β, PDGFR-α/-β; c-KIT) was expressed at significant levels leaving RAF proteins as its likely molecular target. Low sorafenib concentrations paradoxically increased cell viability, whereas higher concentrations induced G1 arrest and eventually apoptosis. MAPK signaling remained partly active after sorafenib treatment, especially in T24 cells with an oncogenic HRAS mutation. AKT phosphorylation was increased, suggesting compensatory activation of the phosphatidylinositol-3-kinase (PI3K) pathway. Sorafenib regularly down regulated the anti-apoptotic myeloid cell leukemia 1 (Mcl-1) protein, but combinatorial treatment with ABT-737 targeting other B-cell lymphoma 2 (Bcl-2) family proteins did not result in synergistic effects. In summary, efficacy of sorafenib in urothelial cancer cell lines appears hampered by limited effects on MAPK signaling, crosstalk with further cancer pathways and an anti-apoptotic state of UCCs. These observations may account for the lack of efficacy of sorafenib in clinical trials and should be considered more broadly in the development of signaling pathway inhibitors for drug therapy in urothelial carcinoma.     

Helicoverpa zea CYP6B8 and CYP321A1: different molecular solutions to the problem of metabolizing plant toxins and insecticides

Under continual exposure to naturally occurring plant toxins and synthetic insecticides, insects have evolved cytochrome P450 monooxygenases (P450s) capable of metabolizing a wide range of structurally different compounds. Two such P450s, CYP6B8 and CYP321A1, expressed in Helicoverpa zea (a lepidopteran) in response to plant allelochemicals and plant signaling molecules metabolize these compounds with varying efficiencies. While sequence alignments of these proteins indicate highly divergent substrate recognition sites (SRSs), homology models developed for them indicate that the two active site cavities have essentially the same volume with distinct shapes dictated by side-chain differences in SRS1 and SRS5. CYP6B8 has a narrower active site cavity extending from substrate access channel pw2a with a very narrow access to the ferryl oxygen atom. This predicted shape suggests that bulkier molecules bind further from the ferryl oxygen at positions that are not as effectively metabolized. In contrast, CYP321A1 is predicted to have a more spacious cavity allowing larger molecules to access the heme-bound oxygen. The metabolic profiles for several plant toxins (xanthotoxin, angelicin) and insecticides (cypermethrin, aldrin and diazinon) correlate well with these predictive models. The absence of Thr in the I helix of CYP321A1 and hydroxyl groups on many of its substrates suggests that this insect P450 mediates oxygen activation by a mechanism different from that employed by CYP107A1 and CYP158A1, which are two bacterial P450s also lacking Thr in their I helix, and most other P450s that contain Thr in their I helix.     

Leaf Age-Dependent Photoprotective and Antioxidative Response Mechanisms to Paraquat-Induced Oxidative Stress in Arabidopsis thaliana

Exposure of Arabidopsis thaliana young and mature leaves to the herbicide paraquat (Pq) resulted in a localized increase of hydrogen peroxide (H₂O₂) in the leaf veins and the neighboring mesophyll cells, but this increase was not similar in the two leaf types. Increased H₂O₂ production was concomitant with closed reaction centers (q_P). Thirty min after Pq exposure despite the induction of the photoprotective mechanism of non-photochemical quenching (NPQ) in mature leaves, H₂O₂ production was lower in young leaves mainly due to the higher increase activity of ascorbate peroxidase (APX). Later, 60 min after Pq exposure, the total antioxidant capacity of young leaves was not sufficient to scavenge the excess reactive oxygen species (ROS) that were formed, and thus, a higher H₂O₂ accumulation in young leaves occurred. The energy allocation of absorbed light in photosystem II (PSII) suggests the existence of a differential photoprotective regulatory mechanism in the two leaf types to the time-course Pq exposure accompanied by differential antioxidant protection mechanisms. It is concluded that tolerance to Pq-induced oxidative stress is related to the redox state of quinone A (Q_A).     

Microbial Resistance Mechanisms to the Antibiotic and Phytotoxin Fusaric Acid

Fusaric acid (FA) produced by Fusarium oxysporum plays an important role in disease development in plants, including cotton. This non-specific toxin also has antibiotic effects on microorganisms. Thus, one expects a potential pool of diverse detoxification mechanisms of FA in nature. Bacteria and fungi from soils infested with Fusarium and from laboratory sources were evaluated for their ability to grow in the presence of FA and to alter the structure of FA into less toxic compounds. None of the bacterial strains were able to chemically modify FA. Highly FA-resistant strains were found only in Gram-negative bacteria, mainly in the genus of Pseudomonas. The FA resistance of the Gram-negative bacteria was positively correlated with the number of predicted genes for FA efflux pumps present in the genome. Phylogenetic analysis of predicted FA resistance proteins (FUSC, an inner membrane transporter component of the efflux pump) revealed that FUSC proteins having high sequence identities with the functionally characterized FA resistance protein FusC or Fdt might be the major contributors of FA resistance. In contrast, most fungi converted FA to less toxic compounds regardless of the level of FA resistance they exhibited. Five derivatives were detected, and the detoxification of FA involved either oxidative reactions on the butyl side chain or reductive reactions on the carboxylic acid group. The production of these metabolites from widely different phyla indicates that resistance to FA by altering its structure is highly conserved. A few FA resistant saprophytic or biocontrol strains of fungi were incapable of altering FA, indicating a possible involvement of efflux transporters. Deployment of both efflux and derivatization mechanisms may be a common feature of fungal FA resistance.     

槐米染色棉织物工艺及其抗紫外性能研究

为实现槐米染料的工业化应用及提高棉织物的功能性,分析了使用壳聚糖、Al3+、Fe2+媒染剂预媒染色法对棉织物染色效果的影响,重点研究了铝预媒染方法染色温度、染色时间、pH值等工艺参数对染色棉织物K/S值的影响,并测试了槐米染色棉织物的抗紫外性能。结果表明:直接使用槐米染色的效果较差;壳聚糖媒染对上染效果影响不大,使用铝、铁媒染剂,可得到不同颜色的棉织物;铝媒染剂染色棉织物为鲜艳的黄色,为较好的媒染方法;铝预媒染染色方法染色优化条件为:温度为80℃,染色时间120分钟,染浴pH值为6.8;铝预媒染染色棉织物具有较好的抗紫外性能。     

灭多威及其混合剂对棉铃虫的杀卵作用和生化机理

用灭多威及其混合剂处理不同发育阶段的棉铃虫卵和初孵幼虫，生化法测定不同发育阶段卵中的乙酰胆碱酯酶，羧酸酯酶活性和蛋白质含量。结果表明，灭多威及其混合剂对初产卵杀卵作用较小，对发育至１日龄以后卵的杀卵作用大；３种混合剂对初孵幼虫的击倒毒力均高于灭多威；该类药剂杀卵作用大小与卵内乙酰胆碱酯酶的活性呈正相关。     

Odor Perception in the Cotton Bollworm,Helicoverpa armigera,Exposed to Juglans regia,a Marginal Host Plant

Journal of Chemical Ecology - The cotton bollworm, Helicoverpa armigera, is one of the most destructive agricultural pests in the world, infesting cotton, maize, soybean, and many other crops. In...     

Latitudinal Gradients in Induced and Constitutive Resistance against Herbivores

Plants are hypothesized to evolve increased defense against herbivores at lower latitudes, but an increasing number of studies report evidence that contradicts this hypothesis. Few studies have examined the evolution of constitutive and induced resistance along latitudinal gradients. When induction is not considered, underlying patterns of latitudinal clines in resistance can be obscured because plant resistance represents a combination of induced and constitutive resistance, which may show contrasting patterns with latitude. Here, we asked if there are latitudinal gradients in constitutive versus induced resistance by using genotypes of Oenothera biennis (Onagraceae) sampled along an 18° latitudinal gradient. We conducted two bioassay experiments to compare the resistance of plant genotypes against one generalist (Spodoptera exigua) and one specialist (Acanthoscelidius acephalus) herbivore. These insects were assayed on: i) undamaged control plants, ii) plants that had been induced with jasmonic acid, and iii) plants induced with herbivore damage. Additionally, we examined latitudinal gradients of constitutive and induced chemical resistance by measuring the concentrations of total phenolics, the concentration of oxidized phenolics, and the percentage of phenolics that were oxidized. Spodoptera exigua showed lower performance on plants from lower latitudes, whereas A. acephalus showed no latitudinal pattern. Constitutive total phenolics were greater in plants from lower latitudes, but induced plants showed higher total phenolics at higher latitudes. Oxidative activity was greatest at higher latitudes regardless of induction. Overall, both latitude and induction have an impact on different metrics of plant resistance to herbivory. Further studies should consider the effect of induction and herbivore specialization more explicitly, which may help to resolve the controversy in latitudinal gradients in herbivory and defense.     

Mechanisms of Resistance to Endocrine Therapy in Breast Cancer: Focus on Signaling Pathways,miRNAs and Genetically Based Resistance

Breast cancer is the most frequent malignancy diagnosed in women. Approximately 70% of breast tumors express the estrogen receptor (ER). Tamoxifen and aromatase inhibitors (AIs) are the most common and effective therapies for patients with ERα-positive breast cancer. Alone or combined with chemotherapy, tamoxifen significantly reduces disease progression and is associated with more favorable impact on survival in patients. Unfortunately, endocrine resistance occurs, either de novo or acquired during the course of the treatment. The mechanisms that contribute to hormonal resistance include loss or modification in the ERα expression, regulation of signal transduction pathways, altered expression of specific microRNAs, balance of co-regulatory proteins, and genetic polymorphisms involved in tamoxifen metabolic activity. Because of the clinical consequences of endocrine resistance, new treatment strategies are arising to make the cells sensitive to tamoxifen. Here, we will review the current knowledge on mechanisms of endocrine resistance in breast cancer cells. In addition, we will discuss novel therapeutic strategies to overcome such resistance. Undoubtedly, circumventing endocrine resistance should help to improve therapy for the benefit of breast cancer patients.     

Behavioral Impairment and Oxidative Damage Induced by Chronic Application of Nonylphenol

Nonylphenol (NP) is a degradation product of nonylphenol polyethoxylates, which are widely used in the production of industrial and consumer surfactants. The aim of the present study was to evaluate the effect of NP on the antioxidant capacity and cognitive ability of mice. NP was given orally by gavages at doses of 0, 50, 100, and 200 mg kg⁻¹ d⁻¹ for 90 days. The results showed that NP significantly decreased the activity of superoxide dismutases (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR) and at the same time increased malondialdehyde (MDA) levels in mice brains. Exploration, memory function and ability to learn a novel task were significantly decreased in NP fed mice. These results indicate that chronic high dose of NP exposure has the potential to generate oxidative stress and induce the cognitive impairment in male mice.     

Extra Virgin Olive Oil Components and Oxidative Stability from Olives Grown in Tunisia

The effects of the contents of lipids, pigments, α-tocopherol and phenols were studied in relation to the antioxidant capacity of five virgin olive oils obtained from five olive cultivars planted in Tunisia (Arbequina, Koroneiki, Leccino, Oueslati and Chemchali). The antioxidant capacities were evaluated by two different radical scavenging activities: radical scavenging activity by the DPPH assay (RSA-DPPH) and total antioxidant status by the ABTS test (TAA-ABTS). The highest contents of antioxidant compounds (75.96, 10.34, 6.32, 15.39 and 241.52 mg kg⁻¹ for oleic acid, O/L ratio, carotenes, chlorophylls and total phenols, respectively) were found for the Koroneiki cultivar except for α-tocopherol and o-diphenols, which had the highest contents (369 and 160.7 mg kg⁻¹, respectively) in the Leccino and Chemchali cultivars (cvs). Furthermore, the highest antioxidant capacity in virgin olive oil was observed in the Koroneiki cultivar (0.24 mmol TE kg⁻¹) followed by the Chemchali and Leccino cvs (0.22 and 0.13 mmol TE kg⁻¹) for the TAA-ABTS test. However, the RSA-DPPH activity was higher for the Chemchali cultivar (19.9%) than for the Koroneiki and Leccino cvs (18.4 and 13.5%, respectively). Correlation between these capacities and the oil composition revealed that they were mainly influenced by the carotene content, followed by chlorophyll and phenolic contents where the ABTS test was more pronounced. Then, the antioxidant capacity of the virgin olive oils was correlated with polar components and the lipid profile which are important for its shelf life.     

寡聚糖与多糖混合诱导蔬菜抗病性的研究

喷施人工合成的植物诱抗剂葡聚六糖与人工发酵的真菌多糖和果胶多糖的混合物,可诱导黄瓜、番茄抗病性的增加,且混合糖的防效要好于各单剂处理。葡聚六糖与多糖混合诱导间隔期为5d时的防效最好,防效达74.6%,7d时无增效作用。     

植物源农药的活性成分和作用机理研究进展

植物源农药因其低毒、低残留和对环境无污染等优点,已引起人们的极大关注,近年来植物源农药研究进展迅速,获得了一批重要成果。本文综述了植物源农药的活性成分、作用机理及特点。     

邻苯二甲酸单丁酯致小鼠肝脏和肾脏组织的氧化损伤

为了探究邻苯二甲酸单丁酯(MBP)对小鼠肝脏和肾脏的氧化损伤,将42只BALB/c小鼠随机分为7组,每组6只,分别为25mg·kg-1、50mg·kg-1、100mg·kg-1、200mg·kg-1的4个MBP染毒组、1个100mg·kg-1的邻苯二甲酸二丁酯(DBP)染毒组、1个空白对照组、1个溶剂对照组。染毒期间对小鼠的体征进行观察;14d后取其肝脏和肾脏组织,制作小鼠肝脏和肾脏组织的切片,对肝脏和肾脏的组织学形态进行观察;制作组织匀浆液用于检测肝脏和肾脏组织细胞的ROS、GSH、MDA的含量,以了解MBP对肝脏和肾脏组织的氧化损伤作用。结果显示:各剂量组小鼠肝细胞和肾小管上皮细胞均出现不同程度的细胞核固缩、细胞水肿、空泡样变、脂肪滴增大融合等症状;ROS和MDA的含量与MBP的染毒剂量呈正相关,GSH的含量与MBP的染毒剂量呈负相关;相同剂量的DBP与MBP染毒组相比,MBP染毒组的ROS和MDA含量较高、GSH含量较低。表明,MBP的暴露与小鼠肝脏和肾脏组织的氧化损伤存在直接联系。