Salivary Glucose Oxidase from Caterpillars Mediates the Induction of Rapid and Delayed-Induced Defenses in the Tomato Plant

Caterpillars produce oral secretions that may serve as cues to elicit plant defenses, but in other cases these secretions have been shown to suppress plant defenses. Ongoing work in our laboratory has focused on the salivary secretions of the tomato fruitworm, Helicoverpa zea. In previous studies we have shown that saliva and its principal component glucose oxidase acts as an effector by suppressing defenses in tobacco. In this current study, we report that saliva elicits a burst of jasmonic acid (JA) and the induction of late responding defense genes such as proteinase inhibitor 2 (Pin2). Transcripts encoding early response genes associated with the JA pathway were not affected by saliva. We also observed a delayed response to saliva with increased densities of Type VI glandular trichomes in newly emerged leaves. Proteomic analysis of saliva revealed glucose oxidase (GOX) was the most abundant protein identified and we confirmed that it plays a primary role in the induction of defenses in tomato. These results suggest that the recognition of GOX in tomato may represent a case for effector-triggered immunity. Examination of saliva from other caterpillar species indicates that saliva from the noctuids Spodoptera exigua and Heliothis virescens also induced Pin2 transcripts

Building pathway clusters from Random Forests classification using class votes

<p>Abstract</p> <p>Background</p> <p>Recent years have seen the development of various pathway-based methods for the analysis of microarray gene expression data. These approaches have the potential to bring biological insights into microarray studies. A variety of methods have been proposed to construct networks using gene expression data. Because individual pathways do not act in isolation, it is important to understand how different pathways coordinate to perform cellular functions. However, there are no published methods describing how to build pathway clusters that are closely related to traits of interest.</p> <p>Results</p> <p>We propose to build pathway clusters from pathway-based classification methods. The proposed methods allow researchers to identify clusters of pathways sharing similar functions. These pathways may or may not share genes. As an illustration, our approach is applied to three human breast cancer microarray data sets. We found that our methods yielded consistent and interpretable results for these three data sets. We further investigated one of the pathway clusters found using PubMatrix. We found that informative genes in the pathway clusters do have more publications with keywords, like estrogen receptor, compared with informative genes in other top pathways. In addition, using the shortest path analysis in GeneGo's MetaCore and Human Protein Reference Database, we were able to identify the links which connect the pathways without shared genes within the pathway cluster.</p> <p>Conclusion</p> <p>Our proposed pathway clustering methods allow bioinformaticians and biologists to investigate how informative genes within pathways are related to each other and understand possible crosstalk between pathways in a cluster. Therefore, building pathway clusters may lead to a better understanding of molecular mechanisms affecting a trait of interest, and help generate further biological hypotheses from gene expression data.</p

Insect Eggs Can Enhance Wound Response in Plants: A Study System of Tomato Solanum lycopersicum L. and Helicoverpa zea Boddie

Insect oviposition on plants frequently precedes herbivory. Accumulating evidence indicates that plants recognize insect oviposition and elicit direct or indirect defenses to reduce the pressure of future herbivory. Most of the oviposition-triggered plant defenses described thus far remove eggs or keep them away from the host plant or their desirable feeding sites. Here, we report induction of antiherbivore defense by insect oviposition which targets newly hatched larvae, not the eggs, in the system of tomato Solanum lycopersicum L., and tomato fruitworm moth Helicoverpa zea Boddie. When tomato plants were oviposited by H. zea moths, pin2, a highly inducible gene encoding protease inhibitor2, which is a representative defense protein against herbivorous arthropods, was expressed at significantly higher level at the oviposition site than surrounding tissues, and expression decreased with distance away from the site of oviposition. Moreover, more eggs resulted in higher pin2 expression in leaves, and both fertilized and unfertilized eggs induced pin2 expression. Notably, when quantified daily following deposition of eggs, pin2 expression at the oviposition site was highest just before the emergence of larvae. Furthermore, H. zea oviposition primed the wound-induced increase of pin2 transcription and a burst of jasmonic acid (JA); tomato plants previously exposed to H. zea oviposition showed significantly stronger induction of pin2 and higher production of JA upon subsequent simulated herbivory than without oviposition. Our results suggest that tomato plants recognize H. zea oviposition as a signal of impending future herbivory and induce defenses to prepare for this herbivory by newly hatched neonate larvae

How Plants Sense Wounds: Damaged-Self Recognition Is Based on Plant-Derived Elicitors and Induces Octadecanoid Signaling

Background: Animal-derived elicitors can be used by plants to detect herbivory but they function only in specific insect– plant interactions. How can plants generally perceive damage caused by herbivores? Damaged-self recognition occurs when plants perceive molecular signals of damage: degraded plant molecules or molecules localized outside their original compartment. Methodology/Principal Findings: Flame wounding or applying leaf extract or solutions of sucrose or ATP to slightly wounded lima bean (Phaseolus lunatus) leaves induced the secretion of extrafloral nectar, an indirect defense mechanism. Chemically related molecules that would not be released in high concentrations from damaged plant cells (glucose, fructose, salt, and sorbitol) did not elicit a detectable response, excluding osmotic shock as an alternative explanation. Treatments inducing extrafloral nectar secretion also enhanced endogenous concentrations of the defense hormone jasmonic acid (JA). Endogenous JA was also induced by mechanically damaging leaves of lima bean, Arabidopsis, maize, strawberry, sesame and tomato. In lima bean, tomato and sesame, the application of leaf extract further increased endogenous JA content, indicating that damaged-self recognition is taxonomically widely distributed. Transcriptomic patterns obtained with untargeted 454 pyrosequencing of lima bean in response to flame wounding or the application of leaf extract or JA were highly similar to each other, but differed from the response to mere mechanical damage. W

Nutritional correlates of koala persistence in a low-density population

It is widely postulated that nutritional factors drive bottom-up, resource-based patterns in herbivore ecology and distribution. There is, however, much controversy over the roles of different plant constituents and how these influence individual herbivores and herbivore populations. The density of koala (Phascolarctos cinereus) populations varies widely and many attribute population trends to variation in the nutritional quality of the eucalypt leaves of their diet, but there is little evidence to support this hypothesis. We used a nested design that involved sampling of trees at two spatial scales to investigate how leaf chemistry influences free-living koalas from a low-density population in south east New South Wales, Australia. Using koala faecal pellets as a proxy for koala visitation to trees, we found an interaction between toxins and nutrients in leaves at a small spatial scale, whereby koalas preferred trees with leaves of higher concentrations of available nitrogen but lower concentrations of sideroxylonals (secondary metabolites found exclusively in eucalypts) compared to neighbouring trees of the same species. We argue that taxonomic and phenotypic diversity is likely to be important when foraging in habitats of low nutritional quality in providing diet choice to tradeoff nutrients and toxins and minimise movement costs. Our findings suggest that immediate nutritional concerns are an important priority of folivores in low-quality habitats and imply that nutritional limitations play an important role in constraining folivore populations. We show that, with a careful experimental design, it is possible to make inferences about populations of herbivores that exist at extremely low densities and thus achieve a better understanding about how plant composition influences herbivore ecology and persistence.IW and WF received a grant from New South Wales (NSW) Department of Environment, Climate Change & Water

Wave-emplaced boulders: implications for development of "prime real estate" seafront, North Coast Jamaica

The final publication is available at Springer via http://dx.doi.org/10.1007/s10064-013-0517-0Jamaica has a long history of damage to the built environment in coastal areas due to storm surge and tsunami. However, there is limited scientific data to aid the establishment of minimal setback distances and to inform mitigation strategies. Developers of coastal area require cost-effective methods to guide their decisions and to develop mitigation strategies to reduce the potential risk posed to development. This paper explores the use of wave-emplaced boulders to determine the wave heights from historical storm surge/tsunami on the North Coast of Jamaica. As most of the study area was undeveloped priory to 1960, there are limited historical written records of storm surges and/or tsunami impact for this specific site. This research undertook geomorphic mapping of the proposed study area to determine the presence, location, spatial distribution, size, density and volume of wave emplaced boulders along a 2-km stretch of coastline earmarked for development. Based on the wave-emplaced boulders mapped, it was possible to determine the approximate wave heights associated with storms and/or tsunami required to deposit them. The implications for development are discussed. The study of wave-emplaced boulders has provided a rapid and cost-effective method to determine minimal setback distance and the approximate height of waves associated with storms and/or tsunami. The technique developed may be transferable to other areas of coastline earmarked for development along the Jamaican coastlin

RNA Silencing of Mcl-1 Enhances ABT-737-Mediated Apoptosis in Melanoma: Role for a Caspase-8-Dependent Pathway

BACKGROUND: Malignant melanoma is resistant to almost all conventional forms of chemotherapy. Recent evidence suggests that anti-apoptotic proteins of the Bcl-2 family are overexpressed in melanoma and may contribute to melanoma's striking resistance to apoptosis. ABT-737, a small-molecule inhibitor of Bcl-2, Bcl-xl and Bcl-w, has demonstrated efficacy in several forms of leukemia, lymphoma as well as solid tumors. However, overexpression of Mcl-1, a frequent observance in melanoma, is known to confer ABT-737 resistance. METHODOLOGY/PRINCIPAL FINDINGS: Here we report that knockdown of Mcl-1 greatly reduces cell viability in combination with ABT-737 in six different melanoma cell lines. We demonstrate that the cytotoxic effect of this combination treatment is due to apoptotic cell death involving not only caspase-9 activation but also activation of caspase-8, caspase-10 and Bid, which are normally associated with the extrinsic pathway of apoptosis. Caspase-8 (and caspase-10) activation is abrogated by inhibition of caspase-9 but not by inhibitors of the death receptor pathways. Furthermore, while caspase-8/-10 activity is required for the full induction of cell death with treatment, the death receptor pathways are not. Finally, we demonstrate that basal levels of caspase-8 and Bid correlate with treatment sensitivity. CONCLUSIONS/SIGNIFICANCE: Our findings suggest that the combination of ABT-737 and Mcl-1 knockdown represents a promising, new treatment strategy for malignant melanoma. We also report a death receptor-independent role for extrinsic pathway proteins in treatment response and suggest that caspase-8 and Bid may represent potential markers of treatment sensitivity

Introduction

Why do parent\u2013child argumentative interactions matter? What is the reason for such an interest? This chapter provides the reasons that motivated the study of parent\u2013child argumentation with the aim to understand the function of this type of interactions. Focusing on the activity of family mealtime, in the first part, the chapter draws attention to the distinctive features of parent\u2013child conversations. A second section of the chapter is devoted to discussing whether and, eventually, when children have the competence to construct arguments and engage in argumentative discussions with the aim to convince their parents to change opinion. In the last part of the chapter, research questions and structure of the volume are presented

The Role of the Proteinase Inhibitor Ovorubin in Apple Snail Eggs Resembles Plant Embryo Defense against Predation

BACKGROUND: Fieldwork has thoroughly established that most eggs are intensely predated. Among the few exceptions are the aerial egg clutches from the aquatic snail Pomacea canaliculata which have virtually no predators. Its defenses are advertised by the pigmented ovorubin perivitellin providing a conspicuous reddish coloration. The nature of the defense however, was not clear, except for a screening for defenses that identified a neurotoxic perivitellin with lethal effect on rodents. Ovorubin is a proteinase inhibitor (PI) whose role to protect against pathogens was taken for granted, according to the prevailing assumption. Through biochemical, biophysical and feeding experiments we studied the proteinase inhibitor function of ovorubin in egg defenses. METHODOLOGY/PRINCIPAL FINDINGS: Mass spectrometry sequencing indicated ovorubin belongs to the Kunitz-type serine proteinase inhibitor family. It specifically binds trypsin as determined by small angle X-ray scattering (SAXS) and cross-linking studies but, in contrast to the classical assumption, it does not prevent bacterial growth. Ovorubin was found extremely resistant to in vitro gastrointestinal proteolysis. Moreover feeding studies showed that ovorubin ingestion diminishes growth rate in rats indicating that this highly stable PI is capable of surviving passage through the gastrointestinal tract in a biologically active form. CONCLUSIONS: To our knowledge, this is the first direct evidence of the interaction of an egg PI with a digestive protease of potential predators, limiting predator's ability to digest egg nutrients. This role has not been reported in the animal kingdom but it is similar to plant defenses against herbivory. Further, this would be the only defense model with no trade-offs between conspicuousness and noxiousness by encoding into the same molecule both the aposematic warning signal and an antinutritive/antidigestive defense. These defenses, combined with a neurotoxin and probably unpalatable factors would explain the near absence of predators, opening new perspectives in the study of the evolution and ecology of egg defensive strategies

5, 8, 11, 14-eicosatetraynoic acid suppresses CCL2/MCP-1 expression in IFN-γ-stimulated astrocytes by increasing MAPK phosphatase-1 mRNA stability

<p>Abstract</p> <p>Background</p> <p>The peroxisome proliferator-activated receptor (PPAR)-α activator, 5,8,11,14-eicosatetraynoic acid (ETYA), is an arachidonic acid analog. It is reported to inhibit up-regulation of pro-inflammatory genes; however, its underlying mechanism of action is largely unknown. In the present study, we focused on the inhibitory action of ETYA on the expression of the chemokine, CCL2/MCP-1, which plays a key role in the initiation and progression of inflammation.</p> <p>Methods</p> <p>To determine the effect of ETYA, primary cultured rat astrocytes and microglia were stimulated with IFN-γ in the presence of ETYA and then, expression of CCL2/MCP-1 and MAPK phosphatase (MKP-1) were determined using RT-PCR and ELISA. MKP-1 mRNA stability was evaluated by treating actinomycin D. The effect of MKP-1 and human antigen R (HuR) was analyzed by using specific siRNA transfection system. The localization of HuR was analyzed by immunocytochemistry and subcellular fractionation experiment.</p> <p>Results</p> <p>We found that ETYA suppressed CCL2/MCP-1 transcription and secretion of CCL2/MCP-1 protein through up-regulation of MKP-1mRNA levels, resulting in suppression of c-Jun N-terminal kinase (JNK) phosphorylation and activator protein 1 (AP1) activity in IFN-γ-stimulated brain glial cells. Moreover, these effects of ETYA were independent of PPAR-α. Experiments using actinomycin D revealed that the ETYA-induced increase in MKP-1 mRNA levels reflected an increase in transcript stability. Knockdown experiments using small interfering RNA demonstrated that this increase in MKP-1 mRNA stability depended on HuR, an RNA-binding protein known to promote enhanced mRNA stability. Furthermore, ETYA-induced, HuR-mediated mRNA stabilization resulted from HuR-MKP-1 nucleocytoplasmic translocation, which served to protect MKP-1 mRNA from the mRNA degradation machinery.</p> <p>Conclusion</p> <p>ETYA induces MKP-1 through HuR at the post-transcriptional level in a receptor-independent manner. The mechanism revealed here suggests eicosanoids as potential therapeutic modulators of inflammation that act through a novel target.</p