Natural mortality factors of Leucoptera coffeella (Lepidoptera: Lyonetiidae) on Coffea arabica

The natural mortality of the coffee leafminer, Leucoptera coffeella (Guérin-Méneville) was investigated in three strata of coffee plant canopy for three seasons through construction and analysis of ecological life tables. Mortality of the leafminer was similar on all thirds of the canopy. Total mortality of immature stages was 95%, with 38.5, 43.8 and 12.7% occurring during egg, larval, and pupal stages. Rainfall killed 39.3% of eggs and larvae, and together with egg inviability (16.3%) and Vespidae (11.3%), were the highest mortality factors. Six wasp parasitoids caused 8% of larval mortality. Egg and larva were the critical stages. Variation in mortality was primarily associated with egg inviability, rainfall, and parasitism by Horismenus sp. (Hymenoptera: Eulophidae). Physiological disturbances during molting and metamorphosis also contributed for fluctuations in mortality of the leafminer. Tactics of integrated pest management to enhance natural mortality of the leafminer while conserving or augmenting the action of natural enemies are discussed.     

Measurements of Cry1F binding and activity of luminal gut proteases in susceptible and Cry1F resistant Ostrinia nubilalis larvae (Lepidoptera: Crambidae)

The biochemical mechanism of resistance to the Bacillus thuringiensis Cry1F toxin was studied in a laboratory-selected strain of Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) showing more than 3000-fold resistance to Cry1F and limited cross resistance to other Cry toxins. Analyses of Cry1F binding to brush border membrane vesicles of midgut epithelia from susceptible and resistant larvae using ligand immunoblotting and Surface Plasmon Resonance (SPR) suggested that reduced binding of Cry1F to insect receptors was not associated with resistance. Additionally, no differences in activity of luminal gut proteases or altered proteolytic processing of the toxin were observed in the resistant strain. Considering these results along with previous evidence of relatively narrow spectrum of cross resistance and monogenic inheritance, the resistance mechanism in this Cry1F selected strain of O. nubilalis appears to be specific and may be distinct from previously identified resistance mechanisms reported in other Lepidoptera.     

Variability of the Mitochondrial SSU rDNA of <Emphasis Type="Italic">Nomuraea</Emphasis> Species and Other Entomopathogenic Fungi from Hypocreales

Hypocrealean arthropod pathogenic fungi have profound impact on the regulation of agricultural and medical pests. However, until now the genetic and phylogenetic relationships among species have not been clarified, such studies could clarify host specificity relationships and define species boundaries. Our purpose was to compare the sequences of the mitochondrial SSU rDNA fragments from several mitosporic entomopathogenic Hypocreales to infer relationships among them and to evaluate the possibility to use these sequences as species diagnostic tool in addition to the more commonly studied sequences of nuclear SSU rDNA. The SSU mt-rDNA proved to be useful to help in differentiation of species inside several genera. Clusters obtained with Parsimony, Bayesian, and Maximum Likelihood analyses were congruent with a new classification of the Clavicipitaceae (Sung et al. Stud Mycol. 2007;57:5-59) in which the anamorphic genera Nomuraea and Metarhizium species remain in the Clavicipitaceae and Isaria species sequenced here are assigned to the family Cordycipitaceae. Mitochondrial genomic information indicates the same general pattern of relationships demonstrated by nuclear gene sequences.     

A Quantile Regression Approach Can Reveal the Effect of Fruit and Vegetable Consumption on Plasma Homocysteine Levels

Introduction

A reduction in homocysteine concentration due to the use of supplemental folic acid is well recognized, although evidence of the same effect for natural folate sources, such as fruits and vegetables (FV), is lacking. The traditional statistical analysis approaches do not provide further information. As an alternative, quantile regression allows for the exploration of the effects of covariates through percentiles of the conditional distribution of the dependent variable.

Objective

To investigate how the associations of FV intake with plasma total homocysteine (tHcy) differ through percentiles in the distribution using quantile regression.

Materials and Methods

A cross-sectional population-based survey was conducted among 499 residents of Sao Paulo City, Brazil. The participants provided food intake and fasting blood samples. Fruit and vegetable intake was predicted by adjusting for day-to-day variation using a proper measurement error model. We performed a quantile regression to verify the association between tHcy and the predicted FV intake. The predicted values of tHcy for each percentile model were calculated considering an increase of 200 g in the FV intake for each percentile.

Results

The results showed that tHcy was inversely associated with FV intake when assessed by linear regression whereas, the association was different when using quantile regression. The relationship with FV consumption was inverse and significant for almost all percentiles of tHcy. The coefficients increased as the percentile of tHcy increased. A simulated increase of 200 g in the FV intake could decrease the tHcy levels in the overall percentiles, but the higher percentiles of tHcy benefited more.

Conclusions

This study confirms that the effect of FV intake on lowering the tHcy levels is dependent on the level of tHcy using an innovative statistical approach. From a public health point of view, encouraging people to increase FV intake would benefit people with high levels of tHcy.     

Indoleamine 2,3-Dioxygenase Controls Fungal Loads and Immunity in Paracoccidioidomicosis but is More Important to Susceptible than Resistant Hosts

Background

Paracoccidioidomycosis, a primary fungal infection restricted to Latin America, is acquired by inhalation of fungal particles. The immunoregulatory mechanisms that control the severe and mild forms of paracoccidioidomycosis are still unclear. Indoleamine 2,3-dioxygenase (IDO), an IFN-γ induced enzyme that catalyzes tryptophan metabolism, can control host-pathogen interaction by inhibiting pathogen growth, T cell immunity and tissue inflammation.

Methodology/Principal Findings

In this study, we investigated the role of IDO in pulmonary paracoccidioidomycosis of susceptible and resistant mice. IDO was blocked by 1-methyl-dl-tryptophan (1MT), and fungal infection studied in vitro and in vivo. Paracoccidioides brasiliensis infection was more severe in 1MT treated than untreated macrophages of resistant and susceptible mice, concurrently with decreased production of kynurenines and IDO mRNA. Similar results were observed in the pulmonary infection. Independent of the host genetic pattern, IDO inhibition reduced fungal clearance but enhanced T cell immunity. The early IDO inhibition resulted in increased differentiation of dendritic and Th17 cells, accompanied by reduced responses of Th1 and Treg cells. Despite these equivalent biological effects, only in susceptible mice the temporary IDO blockade caused sustained fungal growth, increased tissue pathology and mortality rates. In contrast, resistant mice were able to recover the transitory IDO blockade by the late control of fungal burdens without enhanced tissue pathology.

Conclusions/Significance

Our studies demonstrate for the first time that in pulmonary paracoccidioidomycosis, IDO is an important immunoregulatory enzyme that promotes fungal clearance and inhibits T cell immunity and inflammation, with prominent importance to susceptible hosts. In fact, only in the susceptible background IDO inhibition resulted in uncontrolled tissue pathology and mortality rates. Our findings open new perspectives to understand the immunopathology of paracoccidioidomycosis, and suggest that an insufficient IDO activity could be associated with the severe cases of human PCM characterized by inefficient fungal clearance and excessive inflammation.     

Rapid selection and characterization of Cry1F resistance in a Brazilian strain of fall armyworm

Transgenic maize (Zea mays L., Poaceae) event TC1507, producing the Cry1F protein of Bacillus thuringiensis Berliner, has been used for management of the fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), in Brazil since 2009. A strain of S. frugiperda, obtained from field collections of larvae in TC1507 maize in Minas Gerais state in 2010, was selected in the laboratory for resistance to Cry1F using leaves of TC1507 maize in two selection regimes. Continuous exposure of larvae to Cry1F was more effective than exposure for 6, 8, and 10 days in the selection of resistant S. frugiperda individuals. With only four generations of laboratory selection, a strain with high levels of resistance to Cry1F was obtained, as indicated by the survival of insects reared on leaves of TC1507 maize plants and by the more than 300‐fold resistance level measured in bioassays with the purified Cry1F protein. Importantly, reciprocal crosses between control and the Cry1F‐selected strains revealed that the resistance is autosomal and incompletely recessive, and the response obtained in the backcross of the F₁ generation with the resistant strain was consistent with simple monogenic inheritance. Additionally, there were no apparent fitness costs associated with resistance either for survival or larval growth on non‐Bt maize leaves. Our findings provide experimental evidence for rapid evolution of Cry1F resistance in S. frugiperda in the laboratory and further reinforce the potential of this species to evolve field resistance to the TC1507 maize as previously reported. The resistant strain isolated in this study provides an opportunity to estimate the resistance allele frequency in the field and to determine the biochemical and molecular basis of the resistance, which should provide further information to assist in the resistance management of S. frugiperda on transgenic maize producing B. thuringiensis proteins.     

The β-catenin/Tcf4/survivin signaling maintains a less differentiated phenotype and high proliferative capacity of human corneal epithelial progenitor cells

It is clear that the microenvironment or niche plays an important role in determining the fate of stem cells: being stem cells or differentiated. However, the intrinsic pathways controlling the fate of adult stem cells in different niches are largely unknown. This study was to explore the role of β-catenin/Tcf4/survivin signaling in determining the fate of human corneal epithelial stem cells in different media. We observed that the low calcium serum-free media, especially CnT-20, promoted proliferative capacity, colony forming efficiency and stem cell-like phenotype of human corneal epithelial cells (HCECs) when compared with the cells cultured in a high calcium serum-containing medium SHEM. Three key factors in Wnt signaling, β-catenin, Tcf4 and survivin, were found to be expressed higher by HCECs grown in CnT-20 than those cultured in SHEM, as evaluated by real-time PCR, Western blotting and immunostaining. Transfection of siRNA-Tcf4 at 10-50nM knocked down Tcf4, and also significantly suppressed its down stream molecule survivin at both mRNA and protein levels in HCECs. Furthermore, Tcf4 silencing significantly suppressed the proliferative capacity of HCECs, measured by WST-1 assay, compared with the control groups, untreated or transfected with non-coding sequence siRNA-fluorescein. These findings demonstrate that low calcium serum free media promote ex vivo expansion of corneal epithelial progenitor cells that retain a less differentiated phenotype and high proliferative capacity via β-catenin/Tcf4/survivin signaling, a novel intrinsic pathway. This study may have high impact and clinic implication on the expansion of corneal epithelial stem cells in regenerative medicine, especially for ocular surface reconstruction.     

Induced responses of Coffea arabica to attack of Coccus viridis stimulate locomotion of the herbivore

The green scale, Coccus viridis (Green) (Hemiptera: Coccidae), is an insect pest of coffee and several other perennial cultivated plant species. We investigated changes in alkaloid and phenolic contents in coffee plants as a response to herbivory by this insect. Greenhouse‐grown, 11‐month‐old coffee plants were artificially infested with the coccid and compared with control, uninfested plants. Leaf samples were taken at 15, 30, 45, and 60 days after infestation, and high‐performance liquid chromatography was used to identify and quantify alkaloid and phenolic compounds induced by the coccids at each sampling date. Of the compounds investigated, caffeine was the main coffee alkaloid detected in fully developed leaves, and its concentration in infested plants was twice as high as in the control plants. The main coffee phenolics were caffeic and chlorogenic acid, and a significant increase in their concentrations occurred only in plants infested by C. viridis. A positive and significant relationship was found between alkaloid and phenolic concentrations and the infestation level by adults and nymphs of C. viridis. Caffeine and chlorogenic acid applied on coffee leaves stimulated the locomotory activity of the green scale, thus reducing their feeding compared to untreated leaves. This is the first study to show increased levels of coffee alkaloids and phenolics in response to herbivory by scale insects. The elevation of caffeine and chlorogenic acid levels in coffee leaves because of C. viridis infestation seems to affect this generalist insect by stimulating the locomotion of crawlers.     

In Pulmonary Paracoccidioidomycosis IL-10 Deficiency Leads to Increased Immunity and Regressive Infection without Enhancing Tissue Pathology

Background

Cellular immunity is the main defense mechanism in paracoccidioidomycosis (PCM), the most important systemic mycosis in Latin America. Th1 immunity and IFN-γ activated macrophages are fundamental to immunoprotection that is antagonized by IL-10, an anti-inflammatory cytokine. Both in human and experimental PCM, several evidences indicate that the suppressive effect of IL-10 causes detrimental effects to infected hosts. Because direct studies have not been performed, this study was aimed to characterize the function of IL-10 in pulmonary PCM.

Methodology/Principal Findings

Wild type (WT) and IL-10^−/− C57BL/6 mice were used to characterize the role of IL-10 in the innate and adaptive immunity against Paracoccidioides brasiliensis (Pb) infection. We verified that Pb-infected peritoneal macrophages from IL-10^−/− mice presented higher phagocytic and fungicidal activities than WT macrophages, and these activities were associated with elevated production of IFN-γ, TNF-α, nitric oxide (NO) and MCP-1. For in vivo studies, IL-10^−/− and WT mice were i.t. infected with 1×10⁶ Pb yeasts and studied at several post-infection periods. Compared to WT mice, IL-10^−/− mice showed increased resistance to P. brasiliensis infection as determined by the progressive control of pulmonary fungal loads and total clearance of fungal cells from dissemination organs. This behavior was accompanied by enhanced delayed-type hypersensitivity reactions, precocious humoral immunity and controlled tissue pathology resulting in increased survival times. In addition, IL-10^−/− mice developed precocious T cell immunity mediated by increased numbers of lung infiltrating effector/memory CD4⁺ and CD8⁺ T cells. The inflammatory reactions and the production of Th1/Th2/Th17 cytokines were reduced at late phases of infection, paralleling the regressive infection of IL-10^−/− mice.

Conclusions/Significance

Our work demonstrates for the first time that IL-10 plays a detrimental effect to pulmonary PCM due to its suppressive effect on the innate and adaptive immunity resulting in progressive infection and precocious mortality of infected hosts.