Antioxidant and intestinal anti-inflammatory effects of plant-derived coumarin derivatives

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Systematic Screening of Plant Extracts from the Brazilian Pantanal with Antimicrobial Activity against Bacteria with Cariogenic Relevance

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Entoepidemiology of Chagas disease in the Western region of the State of Sao Paulo from 2004 to 2008, and cytogenetic analysis in Rhodnius neglectus (Hemiptera, Triatominae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Impacts of Plant Size, Density, Herbivory, and Desease on Native Platte Thistle (Cirsium Canescens)

Abstract. Based on prior field observations, we hypothesized that individual and interacting effects of plant size, density, insect herbivory, and especially fungal disease, influenced seedling and juvenile plant growth in native Platte thistle populations (Cirsium canescens Nutt.). We worked at Arapaho Prairie in the Nebraska Sandhills (May - August 2007), monitoring plant growth, insect damage, and fungal infection within different density thistle patches. In the main experiment, we sprayed half of test plants in different density patches with fungicide (Fungonil© Bonide, containing chlorothalonil) and half with a water control. Fungal infection rates were very low, so we found no difference in fungal attack between these treatments. However, plants that received the fungicide treatment had significantly faster growth over the season than did the control plants. At the same time, plants in the fungicide treatment had significantly reduced insect herbivory. These results strongly suggest that the fungicide had insecticidal effects and that insect herbivory significantly decreases juvenile Platte thistle growth. Further, damage by insect herbivores tended to be higher for larger plants, and herbivory was variable among different patches. However, plant density did not appear to have a large effect on the amount of insect herbivory that individual juvenile Platte thistle plants received. In the second experiment, we examined germination and survival success in relationship to seed density, and found that germination success was higher in areas of lower seed density. In the third experiment, we tested germination for filled seeds categorized primarily by color variation and size, and found no difference in germination related to either color or seed weight. We conclude that seed density, but not seed quality as estimated by color or size, affects germination success. Further, although herbivory was not significantly affected by plant density at any of the scales examined, insect herbivory significantly reduces the growth and success of juveniles of this characteristic native sand prairie plant.

Psychophysical analysis of contrast processing segregated into magnocellular and parvocellular systems in asymptomatic carriers of 11778 Leber`s hereditary optic neuropathy

We examined achromatic contrast discrimination in asymptomatic carriers of 11778 Leber`s hereditary optic neuropathy (LHON 18 controls) and 18 age-match were also tested. To evaluate magnocellular (MC) and Parvocellular (PC) contrast discrimination, we used a version of Pokorny and Smith`s (1997) Pulsed/steady-pedestal paradigms (PPP/SPP) thought to be detected via PC and MC pathways, respectively. A luminance pedestal (four 1 degrees x 1 degrees squares) was presented on a 12 cd/m(2) surround. The luminance of one of the squares (trial square, TS) was randomly incremented for either 17 or 133 ms. Observers had to detect the TS, in a forced-choice task, at each duration, for three pedestal levels: 7, 12, 19 cd/m(2). In the SPP, the pedestal was fixed, and the TS was modulated. For the PPP, all four pedestal squares pulsed for 17 or 133 ms, and the TS was simultaneously incremented or decremented. We found that contrast discrimination thresholds of LHON carriers were significantly higher than controls` in the condition with the highest luminance of both paradigms, implying impaired contrast processing with no evidence of differential sensitivity losses between the two systems. Carriers` thresholds manifested significantly longer temporal integration than controls in the SPP, consistent with slowed MC responses. The SPP and PPP paradigms can identify contrast and temporal processing deficits in asymptomatic LHON carriers, and thus provide an additional tool for early detection and characterization of the disease.

RNA Interference of Endochitinases in the Sugarcane Endophyte Trichoderma virens 223 Reduces Its Fitness as a Biocontrol Agent of Pineapple Disease

The sugarcane root endophyte Trichoderma virens 223 holds enormous potential as a sustainable alternative to chemical pesticides in the control of sugarcane diseases. Its efficacy as a biocontrol agent is thought to be associated with its production of chitinase enzymes, including N-acetyl-beta-D-glucosaminidases, chitobiosidases and endochitinases. We used targeted gene deletion and RNA-dependent gene silencing strategies to disrupt N-acetyl-beta-D-glucosaminidase and endochitinase activities of the fungus, and to determine their roles in the biocontrol of soil-borne plant pathogens. The loss of N-acetyl-beta-D-glucosaminidase activities was dispensable for biocontrol of the plurivorous damping-off pathogens Rhizoctonia solani and Sclerotinia sclerotiorum, and of the sugarcane pathogen Ceratocystis paradoxa, the causal agent of pineapple disease. Similarly, suppression of endochitinase activities had no effect on R. solani and S. sclerotiorum disease control, but had a pronounced effect on the ability of T. virens 223 to control pineapple disease. Our work demonstrates a critical requirement for T. virens 223 endochitinase activity in the biocontrol of C. paradoxa sugarcane disease, but not for general antagonism of other soil pathogens. This may reflect its lifestyle as a sugarcane root endophyte.

Vesicles as carriers of virulence factors in parasitic protozoan diseases

Different types of shed vesicles as, for example, exosomes, plasma-membrane-derived vesicles or microparticles, are the focus of intense research in view of their potential role in cell cell communication and under the perspective that they might be good tools for immunotherapy, vaccination or diagnostic purposes. This review discusses ways employed by pathogenic trypanosomatids to interact with the host by shedding vesicles that contain molecules important for the establishment of infection, as opposed to previous beliefs considering them as a waste of cellular metabolism. Trypanosomatids are compared with Apicomplexa, which circulate parasite antigens bound to vesicles shed by host cells. The knowledge of the origin and chemical composition of these different vesicles might lead to the understanding of the mechanisms that determine their biological function. (C) 2012 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

An Extreme Case of Plant-Insect Codiversification: Figs and Fig-Pollinating Wasps

It is thought that speciation in phytophagous insects is often due to colonization of novel host plants, because radiations of plant and insect lineages are typically asynchronous. Recent phylogenetic comparisons have supported this model of diversification for both insect herbivores and specialized pollinators. An exceptional case where contemporaneous plant-insect diversification might be expected is the obligate mutualism between fig trees (Ficus species, Moraceae) and their pollinating wasps (Agaonidae, Hymenoptera). The ubiquity and ecological significance of this mutualism in tropical and subtropical ecosystems has long intrigued biologists, but the systematic challenge posed by >750 interacting species pairs has hindered progress toward understanding its evolutionary history. In particular, taxon sampling and analytical tools have been insufficient for large-scale cophylogenetic analyses. Here, we sampled nearly 200 interacting pairs of fig and wasp species from across the globe. Two supermatrices were assembled: on an average, wasps had sequences from 77% of 6 genes (5.6 kb), figs had sequences from 60% of 5 genes (5.5 kb), and overall 850 new DNA sequences were generated for this study. We also developed a new analytical tool, Jane 2, for event-based phylogenetic reconciliation analysis of very large data sets. Separate Bayesian phylogenetic analyses for figs and fig wasps under relaxed molecular clock assumptions indicate Cretaceous diversification of crown groups and contemporaneous divergence for nearly half of all fig and pollinator lineages. Event-based cophylogenetic analyses further support the codiversification hypothesis. Biogeographic analyses indicate that the present-day distribution of fig and pollinator lineages is consistent with a Eurasian origin and subsequent dispersal, rather than with Gondwanan vicariance. Overall, our findings indicate that the fig-pollinator mutualism represents an extreme case among plant-insect interactions of coordinated dispersal and long-term codiversification.

Consequences of plant population size for pollinator visitation and plant reproductive success

Habitat loss and fragmentation have a prominent role in determining the size of plant populations, and can affect plant-pollinator interactions. It is hypothesized that in small plant populations the ability to set seeds can be reduced due to limited pollination services, since individuals in small populations can receive less quantity or quality of visits. In this study, I investigated the effect of population size on plant reproductive success and insect visitation in 8 populations of two common species in the island of Lesvos, Greece (Mediterranean Sea), Echium plantagineum and Ballota acetabulosa, and of a rare perennial shrub endemic to north-central Italy, Ononis masquillierii. All the three species depended on insect pollinators for sexual reproduction. For each species, pollen limitation was present in all or nearly all populations, but the relationship between pollen limitation and population size was only present in Ononis masquillierii. However, in Echium plantagineum, significant relationships between both open-pollinated and handcrossed-pollinated seed sets and population size were found, being small populations comparatively less productive than large ones. Additionally, for this species, livestock grazing intensity was greater for small populations and for sparse patches, and had a negative influence on productivity of the remnant plants. Both Echium plantagineum and Ballota acetabulosa attracted a great number of insects, representing a wide spectrum of pollinators, thereby can be considered as generalist species. For Ballota acetabulosa, the most important pollinators were megachilid female bees, and insect diversity didn’t decrease with decreasing plant population size. By contrast, Ononis masquillierii plants generally received few visits, with flowers specialized on small bees (Lasioglossum spp.), representing the most important insect guild. In Echium plantagineum and Ballota acetabulosa, plants in small and large populations received the same amount of visits per flower, and no differences in the number of intraplant visited flowers were detected. On the contrary, large Ononis populations supported higher amounts of pollinators than small ones. At patch level, high Echium flower density was associated with more and higher quality pollinators. My results indicate that small populations were not subject to reduced pollination services than large ones in Echium plantagineum and Ballota acetabulosa, and suggest that grazing and resource limitation could have a major impact on population fitness in Echium plantagineum. The absence of any size effects in these two species can be explained in the light of their high local abundance, wide habitat specificity, and ability to compete with other co-flowering species for pollinators. By contrast, size represents a key characteristic for both pollination and reproduction in Ononis masquillierii populations, as an increase in size could mitigate the negative effects coming from the disadvantageous reproductive traits of the species. Finally, the widespread occurrence of pollen limitation in the three species may be the result of 1) an ongoing weakening or disruption of plantpollinator interactions derived from ecological perturbations, 2) an adaptive equilibrium in response to stochastic processes, and 3) the presence of unfavourable reproductive traits (for Ononis masquillierii).

The impact of plant diversity and fertilization on fitness of a generalist grasshopper

In many environments land use intensification is likely to result in a decrease in species richness and in an increase in eutrophication. Although the importance of both factors for higher trophic levels such as insect herbivores is well documented, their impact has rarely been studied in combination. Herbivorous insects have a strong impact on the functioning of ecosystems and it is therefore important to understand how they are affected by eutrophication in high or low diversity environments. We used a grassland biodiversity experiment to investigate the combined effect of fertilization and plant diversity loss on the fitness of the generalist grasshopper Chorthippus parallelus by rearing grasshopper nymphs for four weeks in cages on unfertilized or fertilized (NPK) subplots across a species richness gradient from 1 to 60 plant species. Survival, the number of oothecae, body mass and the number of hatchlings were measured separately for each cage. Plant diversity had no effect on any of the grasshopper fitness measures, neither in unfertilized nor in fertilized plots. NPK-fertilization reduced grasshopper survival but increased body mass of males and reproductive success of the surviving females. Fertilization effects were not mediated by plant community structure, productivity or composition, suggesting that higher food plant quality was one of the main drivers. There was no interaction between plant diversity and fertilization on any of the measures. In conclusion, an increase in eutrophication, in both species-rich and species-poor grasslands, could lead to higher reproductive success and therefore higher abundances of herbivorous insects including insect pests, with fertilization effects dominating plant diversity effects.

Seroprevalence of Chagas' disease in Texas among shelter dogs in Houston and the Rio Grande Valley region and its implication for human infection

Chagas’ disease, also called American Trypanosomiasis, is a vector-borne disease caused by the protozoan parasite Trypanosoma cruzi. T. cruzi is spread by triatomine insects, commonly referred to as ‘kissing bugs.’ After the insect takes a blood meal from its animal or human host, it usually defecates near the bite wound. The parasite is present in the feces, and when rubbed into the bite wound or mucous membranes by the host, infection ensues. Chagas’ disease is highly endemic in Central and South America where it originated. Many people in these endemic areas live in poor conditions surrounded by animals, mainly dogs, that can serve as a possible link to human infection. In Chagas’ endemic countries, dogs can be used as a sentinel to infer risk for human infection. In Texas, the prevalence of Chagas’ and risk for human infection is largely unknown. This study aimed to determine the prevalence of Chagas’ disease in shelter dogs in Houston, Texas and the Rio Grande Valley region by using an immunochromatographic assay (Chagas’ Stat-Pak) to test for the presence of T. cruzi antibodies. Of the 822 samples tested, 26 were found to be positive (3.2%). In both locations, Chagas’ prevalence increased over time. This study found that dogs, especially strays, can serve as sentinels for disease activity. Public health authorities can implement this strategy to understand the level of Chagas’ activity in a defined geographic area and prevent human infection.^

Inactivation of the mitogen-activated protein kinase Mps1 from the rice blast fungus prevents penetration of host cells but allows activation of plant defense responses

The rice blast fungus, Magnaporthe grisea, generates enormous turgor pressure within a specialized cell called the appressorium to breach the surface of host plant cells. Here, we show that a mitogen-activated protein kinase, Mps1, is essential for appressorium penetration. Mps1 is 85% similar to yeast Slt2 mitogen-activated protein kinase and can rescue the thermosensitive growth of slt2 null mutants. The mps1–1Δ mutants of M. grisea have some phenotypes in common with slt2 mutants of yeast, including sensitivity to cell-wall-digesting enzymes, but display additional phenotypes, including reduced sporulation and fertility. Interestingly, mps1–1Δ mutants are completely nonpathogenic because of the inability of appressoria to penetrate plant cell surfaces, suggesting that penetration requires remodeling of the appressorium wall through an Mps1-dependent signaling pathway. Although mps1–1Δ mutants are unable to cause disease, they are able to trigger early plant-cell defense responses, including the accumulation of autofluorescent compounds and the rearrangement of the actin cytoskeleton. We conclude that MPS1 is essential for pathogen penetration; however, penetration is not required for induction of some plant defense responses.

Enhancement of induced disease resistance by simultaneous activation of salicylate- and jasmonate-dependent defense pathways in Arabidopsis thaliana

The plant-signaling molecules salicylic acid (SA) and jasmonic acid (JA) play an important role in induced disease resistance pathways. Cross-talk between SA- and JA-dependent pathways can result in inhibition of JA-mediated defense responses. We investigated possible antagonistic interactions between the SA-dependent systemic acquired resistance (SAR) pathway, which is induced upon pathogen infection, and the JA-dependent induced systemic resistance (ISR) pathway, which is triggered by nonpathogenic Pseudomonas rhizobacteria. In Arabidopsis thaliana, SAR and ISR are effective against a broad spectrum of pathogens, including the foliar pathogen Pseudomonas syringae pv. tomato (Pst). Simultaneous activation of SAR and ISR resulted in an additive effect on the level of induced protection against Pst. In Arabidopsis genotypes that are blocked in either SAR or ISR, this additive effect was not evident. Moreover, induction of ISR did not affect the expression of the SAR marker gene PR-1 in plants expressing SAR. Together, these observations demonstrate that the SAR and the ISR pathway are compatible and that there is no significant cross-talk between these pathways. SAR and ISR both require the key regulatory protein NPR1. Plants expressing both types of induced resistance did not show elevated Npr1 transcript levels, indicating that the constitutive level of NPR1 is sufficient to facilitate simultaneous expression of SAR and ISR. These results suggest that the enhanced level of protection is established through parallel activation of complementary, NPR1-dependent defense responses that are both active against Pst. Therefore, combining SAR and ISR provides an attractive tool for the improvement of disease control.

Biochemical Analysis of Plant Protection Afforded by a Nonpathogenic Endophytic Mutant of Colletotrichum magna1

A nonpathogenic mutant of Colletotrichum magna (path-1) was previously shown to protect watermelon (Citrullus lanatus) and cucumber (Cucumis sativus) seedlings from anthracnose disease elicited by wild-type C. magna. Disease protection was observed in stems of path-1-colonized cucurbits but not in cotyledons, indicating that path-1 conferred tissue-specific and/or localized protection. Plant biochemical indicators of a localized and systemic (peroxidase, phenylalanine ammonia-lyase, lignin, and salicylic acid) “plant-defense” response were investigated in anthracnose-resistant and -susceptible cultivars of cucurbit seedlings exposed to four treatments: (1) water (control), (2) path-1 conidia, (3) wild-type conidia, and (4) challenge conditions (inoculation into path-1 conidia for 48 h and then exposure to wild-type conidia). Collectively, these analyses indicated that disease protection in path-1-colonized plants was correlated with the ability of these plants to mount a defense response more rapidly and to equal or greater levels than plants exposed to wild-type C. magna alone. Watermelon plants colonized with path-1 were also protected against disease caused by Colletotrichum orbiculare and Fusarium oxysporum. A model based on the kinetics of plant-defense activation is presented to explain the mechanism of path-1-conferred disease protection.

The PR5K receptor protein kinase from Arabidopsis thaliana is structurally related to a family of plant defense proteins.

We have isolated an Arabidopsis thaliana gene that codes for a receptor related to antifungal pathogenesis-related (PR) proteins. The PR5K gene codes for a predicted 665-amino acid polypeptide that comprises an extracellular domain related to the PR5 proteins, a central transmembrane-spanning domain, and an intracellular protein-serine/threonine kinase. The extracellular domain of PR5K (PR5-like receptor kinase) is most highly related to acidic PR5 proteins that accumulate in the extracellular spaces of plants challenged with pathogenic microorganisms. The kinase domain of PR5K is related to a family of protein-serine/threonine kinases that are involved in the expression of self-incompatibility and disease resistance. PR5K transcripts accumulate at low levels in all tissues examined, although particularly high levels are present in roots and inflorescence stems. Treatments that induce authentic PR5 proteins had no effect on the level of PR5K transcripts, suggesting that the receptor forms part of a preexisting surveillance system. When the kinase domain of PR5K was expressed in Escherichia coli, the resulting polypeptide underwent autophosphorylation, consistent with its predicted enzyme activity. These results are consistent with PR5K encoding a functional receptor kinase. Moreover, the structural similarity between the extracellular domain of PR5K and the antimicrobial PR5- proteins suggests a possible interaction with common or related microbial targets.