Sexually Dimorphic Intrasexual Duetting in an Otherwise Monomorphic Green Lacewing (Neuroptera, Chrysopidae, Chrysoperla plorabunda): Sexual Selection or Sex Recognition?

Songs produced during heterosexual duets in a green lacewing, C. plorabunda, are sexually monomorphic. However, individuals of either sex will also engage in intrasexual duets, which can exhibit sexual dimorphism. We confined males and females together in various combinations in a small arena to study the phenotypes, behavioral interactions, and functional roles of duetting in this species. The goal was to test whether sexual selection or sex recognition provided the better explanation of song sexual dimorphism. We determined that the monomorphic form of the intrasexual duet was long and stable, and could take place either between males or between females. Such “standard” intrasexual duetting songs were acoustically indistinguishable from heterosexual songs. However, males could also engage other males in special “fast duets” that sped up and terminated abruptly. Equivalent fast duets were not part of the female repertory. Fast duetting songs between males differed significantly from other types of male or female duetting songs in every measurable characteristic, but their role in the mating system was ambiguous. Contrary to one prediction of the sexual selection hypothesis, fast duetting between males occurred less often in situations where it might be the most useful to males in securing mates, i.e., during male-male-female interactions (trios). In addition, fast songs that started, ended, both started and ended, or neither started nor ended duets were acoustically indistinguishable, making it unlikely that females were choosing males based on such variation. However, songs that “both started and ended” fast duets were associated with a significant mating advantage, indicating a possible role for fast duetting in male-male sexual competition. Because the alternative hypothesis of sex recognition was also supported by some of our results, we conclude that aggressive qualities of male-male fast duets probably mediate intrasexual selection, while their increasing tempo serves as an adaptive response to promote rapid sex recognition by truncating unproductive and potentially dangerous intrasexual duetting.     

Testing the usefulness of a simple automatic method for particles abundance and size determination to derive cost-effective biological indicators in large monitoring networks

A simple automatic method has been tested for biological quality assessment in coastal and estuarine waters. Samples collected in routine campaigns along the Basque coast (northern Spain) were analysed by both, a traditional microscopy technique (Utermöhl) and the flow cytometer and microscope (FlowCAM). The FlowCAM was operated in AutoImage mode (i.e. without fluorescence measurements). Two different FlowCAM procedures were carried out in two campaigns separately (2005 and 2008). These differed mainly in the lower size-threshold of the particles sampled: 10 μm in 2005, and 4 μm in 2008. The degree of divergence was evaluated, recognizing that the Utermöhl method and the FlowCAM (as employed here) count differently (i.e. phytoplankton cells and particles, respectively). In general, higher concentrations were observed with the FlowCAM (although there were some exceptions in 2005). Relationships between physico-chemical and FlowCAM variables were studied and patterns of natural variability were identified. However, a clear response to nutrient pressure was not found. It is concluded that the potential of this automatic method for deriving cost-effective indicators is limited, especially in estuaries, due to the high interference with suspended material. Further studies incorporating fluorescence measurements with the FlowCAM may be more promising. The standardization of procedures is highly recommended.     

Resurrecting complexity: the interplay of plasticity and rapid evolution in the multiple trait response to strong changes in predation pressure in the water flea Daphnia magna

A resurrection ecology reconstruction of 14 morphological, life history and behavioural traits revealed that a natural Daphnia magna population rapidly tracked changes in fish predation by integrating phenotypic plasticity and widespread evolutionary changes both in mean trait values and in trait plasticity. Increased fish predation mainly generated rapid adaptive evolution of plasticity (especially in the presence of maladaptive ancestral plasticity) resulting in an important change in the magnitude and direction of the multivariate reaction norm. Subsequent relaxation of the fish predation pressure resulted in reversed phenotypic plasticity and mainly caused evolution of the trait means towards the ancestral pre‐fish means. Relaxation from fish predation did, however, not result in a complete reversal to the ancestral fishless multivariate phenotype. Our study emphasises that the study population rapidly tracked environmental changes through a mosaic of plasticity, evolution of trait means and evolution of plasticity to generate integrated phenotypic changes in multiple traits.     

Food supplementation to optimize inoculative release of the predatory bug Macrolophus pygmaeus in sweet pepper

Biological control is widespread in management of greenhouse sweet pepper crops. Several species of predatory mites, bugs, and parasitoids are used against a wide range of pest species. However, biological control of particular pests like aphids, caterpillars, and the tobacco whitefly, Bemisia tabaci Gennadius, remains problematic. Macrolophus pygmaeus Rambur (Hemiptera: Miridae) is a generalist predatory bug which is used on a large scale in Western European tomato greenhouses. It has already been demonstrated that M. pygmaeus is a valuable biocontrol option in sweet pepper crops, but it has yet to find its way into common practice. Macrolophus pygmaeus should be introduced at the start of the growing season and determining an optimal release strategy is a key step in this process. In tomato crops, M. pygmaeus requires supplemental food releases to reach sufficient population numbers and dispersal levels. In this study, the need for food supplementation in sweet pepper is investigated. Three strategies were tested: (1) no food supplementation, (2) local food supplementation, and (3) full field food supplementation. Both population numbers and dispersal rates of the second generation were higher under the third strategy. Macrolophus pygmaeus oviposits near food sources, therefore dispersal rates are higher when food is more spread out. Pest control was achieved in all treatments, but faster and at lower pest levels under the full field strategy.     

Reciprocal regulation between natural killer cells and autoreactive T cells

The initiation and the progression of autoimmune diseases stem from complex interactions that involve cells of both the innate and the adaptive immune system. As we discuss here, natural killer (NK) cells, which are components of the innate immune system, can inhibit or promote the activation of autoreactive T cells during the initiation of autoimmunity. After they have been activated, autoreactive T cells contribute to the homeostatic contraction of NK-cell populations. The dynamic interaction between NK cells and autoreactive T cells might indicate the transition from the innate immune triggering of autoimmunity to the progressive phase of the disease. Understanding the mechanisms and signals that control the reciprocal regulation of NK cells and autoreactive T cells could have important implications for treatment in the clinic.     

Genes suppressed by DNA methylation in non-small cell lung cancer reveal the epigenetics of epithelial–mesenchymal transition

Background

DNA methylation is associated with aberrant gene expression in cancer, and has been shown to correlate with therapeutic response and disease prognosis in some types of cancer. We sought to investigate the biological significance of DNA methylation in lung cancer.

Results

We integrated the gene expression profiles and data of gene promoter methylation for a large panel of non-small cell lung cancer cell lines, and identified 578 candidate genes with expression levels that were inversely correlated to the degree of DNA methylation. We found these candidate genes to be differentially methylated in normal lung tissue versus non-small cell lung cancer tumors, and segregated by histologic and tumor subtypes. We used gene set enrichment analysis of the genes ranked by the degree of correlation between gene expression and DNA methylation to identify gene sets involved in cellular migration and metastasis. Our unsupervised hierarchical clustering of the candidate genes segregated cell lines according to the epithelial-to-mesenchymal transition phenotype. Genes related to the epithelial-to-mesenchymal transition, such as AXL, ESRP1, HoxB4, and SPINT1/2, were among the nearly 20% of the candidate genes that were differentially methylated between epithelial and mesenchymal cells. Greater numbers of genes were methylated in the mesenchymal cells and their expressions were upregulated by 5-azacytidine treatment. Methylation of the candidate genes was associated with erlotinib resistance in wild-type EGFR cell lines. The expression profiles of the candidate genes were associated with 8-week disease control in patients with wild-type EGFR who had unresectable non-small cell lung cancer treated with erlotinib, but not in patients treated with sorafenib.

Conclusions

Our results demonstrate that the underlying biology of genes regulated by DNA methylation may have predictive value in lung cancer that can be exploited therapeutically.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-1079) contains supplementary material, which is available to authorized users.     

Decline in HIV Prevalence among Young Men in the General Population of Cotonou, Benin, 1998-2008

Objective

To assess changes in the prevalence of HIV and other sexually transmitted infections, as well as in different proximal and distal factors related to HIV infection, in the general population of Cotonou between 1998 and 2008, while an intensive preventive intervention targeting the sex work milieu was ongoing.

Methods

A two-stage cluster sampling procedure was used to select the participants in each study. Subjects aged 15–49 who agreed to participate were interviewed and tested for HIV, syphilis, HSV-2, gonorrhoea and chlamydia. We used the Roa-Scott Chi-square test (proportions) and the Student’s t test (means) for bivariate comparisons, and adjusted logistic regression models taking into account the cluster effect for multivariate analyses.

Results

HIV prevalence decreased significantly in men (3.4% in 1998 versus 2.0% in 2008, p = 0.048), especially in those aged 15–29 (3.0% to 0.5%, p = 0.002). Among men, the prevalence of gonorrhoea decreased significantly (1.1% to 0.3%, p = 0.046) while HSV-2 prevalence increased from 12.0% to 18.1% (p = 0.0003). The proportion of men who reported condom use at least once (29.3% to 61.0%, p<0.0001) and of those having attained a secondary educational level or more (17.1% to 61.3%, p<0.0001) also increased significantly. There was an overall decrease in the prevalence of syphilis (1.5% to 0.6%, p = 0.0003).

Conclusion

This is the first population-based study reporting a significant decline in HIV prevalence among young men in an African setting where overall prevalence has never reached 5%. The decline occurred while preventive interventions targeting the sex work milieu were ongoing and the educational level was increasing.     

Niche breadth,rarity and ecological characteristics within a regional flora spanning large environmental gradients

Aim Species specialization, which plays a fundamental role in niche differentiation and species coexistence, is a key biological trait in relation to the responses of populations to changing environments. Species with a limited niche breadth are considered to experience a higher risk of extinction than generalist species. This work aims to measure the degree of specialization in the regional flora of the French Alps and test whether species specialization is related to species rarity and ecological characteristics. Location This study was conducted in the French Alps region, which encompasses a large elevational gradient over a relatively limited area (26,000 km²). Methods Specialization was estimated for approximately 1200 plant species found in the region. Given the inherent difficulty of pinpointing the critical environmental niche axes for each individual species, we used a co‐occurrence‐based index to estimate species niche breadths (specialization index). This comprehensive measurement included crucial undetermined limiting niche factors, acting on both local and regional scales, and related to both biotic and abiotic interactions. The specialization index for each species was then related to a selection of plant typologies such as Grime strategies and Raunkiaer life‐forms, and to two measurements of plant rarity, namely regional area of occupancy and local abundance. Results Specialist species were mainly found in specific and harsh environments such as wetlands, cold alpine habitats and dry heathlands. These species were usually geographically restricted but relatively dominant in their local communities. Although none of the selected traits were sufficient predictors of specialization, pure competitors were over‐represented amongst generalist species, whereas stress‐tolerant species tended to be more specialized. Main conclusions Our results suggest that co‐occurrence‐based indices of niche breadth are a satisfactory method for inferring plant specialization using large species samples across very heterogeneous environments. Our results are an empirical validation of the tolerance–dominance trade‐off and also provide interesting insights into the long‐standing question of which biological properties characterize species with narrow niche breadth that are potentially threatened by global changes in the environment.     

A bioanalytical method for the proteome wide display and analysis of protein complexes from whole plant cell lysates

While protein interaction studies and protein network modeling come to the forefront, the isolation and identification of protein complexes in a cellular context remains a major challenge for plant science. To this end, a nondenaturing extraction procedure was optimized for plant whole cell matrices and the combined use of gel filtration and BN‐PAGE for the separation of protein complexes was studied. Hyphenation to denaturing electrophoresis and mass spectrometric analysis allows for the simultaneous identification of multiple (previously unidentified) protein interactions in single samples. The reliability and efficacy of the technique was confirmed (i) by the identification of well‐studied plant protein complexes, (ii) by the presence of nonplant interologs for several of the novel complexes (iii) by presenting physical evidence of previously hypothetical plant protein interactions and (iv) by the confirmation of found interactions using co‐IP. Furthermore practical issues concerning the use of this 2‐D BN/SDS‐PAGE display method for the analysis of protein–protein interactions are discussed.     

Do antheridiogens act via gametophyte size? A study of Woodwardia radicans (Blechnaceae)

For many plants, sex is not fixed by genotype but determined by environmental conditions during development. In homosporous pteridophytes, sex is environmentally determined by the presence or absence of antheridiogens, maleness-inducing pheromones. It has been proposed that antheridiogens primarily reduce growth rate, with small gametophyte size responsible for maleness. To test this hypothesis, the effects of antheridiogen and intergametophytic competition on gender expression and gametophyte size were studied in a culture experiment with Woodwardia radicans. We found that (1) antheridiogen inhibited growth of gametophytes; and (2) slow growth favored maleness, whereas fast growth favored femaleness, irrespective of the presence or absence of antheridiogen. Both conclusions are consistent with the hypothesis that, in W. radicans, antheridiogen effect is mediated by size. They also agree with the "size-advantage" hypothesis in which energetic limitations associated with relatively small individual size impose a less severe limitation for male reproductive success than for female reproductive success. The results are also discussed with regard to a genetic sex-determining pathway that has recently been identified.