A transcriptomic snapshot of early molecular communication between Pasteuria penetrans and Meloidogyne incognita

© The Author(s). 2018Background: Southern root-knot nematode Meloidogyne incognita (Kofoid and White, 1919), Chitwood, 1949 is a key pest of agricultural crops. Pasteuria penetrans is a hyperparasitic bacterium capable of suppressing the nematode reproduction, and represents a typical coevolved pathogen-hyperparasite system. Attachment of Pasteuria endospores to the cuticle of second-stage nematode juveniles is the first and pivotal step in the bacterial infection. RNA-Seq was used to understand the early transcriptional response of the root-knot nematode at 8 h post Pasteuria endospore attachment. Results: A total of 52,485 transcripts were assembled from the high quality (HQ) reads, out of which 582 transcripts were found differentially expressed in the Pasteuria endospore encumbered J2 s, of which 229 were up-regulated and 353 were down-regulated. Pasteuria infection caused a suppression of the protein synthesis machinery of the nematode. Several of the differentially expressed transcripts were putatively involved in nematode innate immunity, signaling, stress responses, endospore attachment process and post-attachment behavioral modification of the juveniles. The expression profiles of fifteen selected transcripts were validated to be true by the qRT PCR. RNAi based silencing of transcripts coding for fructose bisphosphate aldolase and glucosyl transferase caused a reduction in endospore attachment as compared to the controls, whereas, silencing of aspartic protease and ubiquitin coding transcripts resulted in higher incidence of endospore attachment on the nematode cuticle. Conclusions: Here we provide evidence of an early transcriptional response by the nematode upon infection by Pasteuria prior to root invasion. We found that adhesion of Pasteuria endospores to the cuticle induced a down-regulated protein response in the nematode. In addition, we show that fructose bisphosphate aldolase, glucosyl transferase, aspartic protease and ubiquitin coding transcripts are involved in modulating the endospore attachment on the nematode cuticle. Our results add new and significant information to the existing knowledge on early molecular interaction between M. incognita and P. penetrans.Peer reviewedFinal Published versio

Mathematics and biology: a Kantian view on the history of pattern formation theory

Driesch’s statement, made around 1900, that the physics and chemistry of his day were unable to explain self-regulation during embryogenesis was correct and could be extended until the year 1972. The emergence of theories of self-organisation required progress in several areas including chemistry, physics, computing and cybernetics. Two parallel lines of development can be distinguished which both culminated in the early 1970s. Firstly, physicochemical theories of self-organisation arose from theoretical (Lotka 1910–1920) and experimental work (Bray 1920; Belousov 1951) on chemical oscillations. However, this research area gained broader acceptance only after thermodynamics was extended to systems far from equilibrium (1922–1967) and the mechanism of the prime example for a chemical oscillator, the Belousov–Zhabotinski reaction, was deciphered in the early 1970s. Secondly, biological theories of self-organisation were rooted in the intellectual environment of artificial intelligence and cybernetics. Turing wrote his The chemical basis of morphogenesis (1952) after working on the construction of one of the first electronic computers. Likewise, Gierer and Meinhardt’s theory of local activation and lateral inhibition (1972) was influenced by ideas from cybernetics. The Gierer–Meinhardt theory provided an explanation for the first time of both spontaneous formation of spatial order and of self-regulation that proved to be extremely successful in elucidating a wide range of patterning processes. With the advent of developmental genetics in the 1980s, detailed molecular and functional data became available for complex developmental processes, allowing a new generation of data-driven theoretical approaches. Three examples of such approaches will be discussed. The successes and limitations of mathematical pattern formation theory throughout its history suggest a picture of the organism, which has structural similarity to views of the organic world held by the philosopher Immanuel Kant at the end of the eighteenth century

Spatial gene expression quantification: a tool for analysis of <it>in situ </it>hybridizations in sea anemone <it>Nematostella vectensis</it>

<p>Abstract</p> <p>Background</p> <p>Spatial gene expression quantification is required for modeling gene regulation in developing organisms. The fruit fly <it>Drosophila melanogaster</it> is the model system most widely applied for spatial gene expression analysis due to its unique embryonic properties: the shape does not change significantly during its early cleavage cycles and most genes are differentially expressed along a straight axis. This system of development is quite exceptional in the animal kingdom.</p> <p>In the sea anemone <it>Nematostella vectensis</it> the embryo changes its shape during early development; there are cell divisions and cell movement, like in most other metazoans. <it>Nematostella</it> is an attractive case study for spatial gene expression since its transparent body wall makes it accessible to various imaging techniques.</p> <p>Findings</p> <p>Our new quantification method produces standardized gene expression profiles from raw or annotated <it>Nematostella in situ</it> hybridizations by measuring the expression intensity along its cell layer. The procedure is based on digital morphologies derived from high-resolution fluorescence pictures. Additionally, complete descriptions of nonsymmetric expression patterns have been constructed by transforming the gene expression images into a three-dimensional representation.</p> <p>Conclusions</p> <p>We created a standard format for gene expression data, which enables quantitative analysis of <it>in situ</it> hybridizations from embryos with various shapes in different developmental stages. The obtained expression profiles are suitable as input for optimization of gene regulatory network models, and for correlation analysis of genes from dissimilar <it>Nematostella</it> morphologies. This approach is potentially applicable to many other metazoan model organisms and may also be suitable for processing data from three-dimensional imaging techniques.</p

Trypanosomiasis-induced B cell apoptosis results in loss of protective anti-parasite antibody responses and abolishment of vaccine-induced memory responses.

African trypanosomes of the Trypanosoma brucei species are extra-cellular parasites that cause human African trypanosomiasis (HAT) as well as infections in game animals and livestock. Trypanosomes are known to evade the immune response of their mammalian host by continuous antigenic variation of their surface coat. Here, we aim to demonstrate that in addition, trypanosomes (i) cause the loss of various B cell populations, (ii) disable the hosts' capacity to raise a long-lasting specific protective anti-parasite antibody response, and (iii) abrogate vaccine-induced protective response to a non-related human pathogen such as Bordetella pertussis. Using a mouse model for T. brucei, various B cell populations were analyzed by FACS at different time points of infection. The results show that during early onset of a T. brucei infection, spleen remodeling results in the rapid loss of the IgM(+) marginal zone (IgM(+)MZ) B cell population characterized as B220(+)IgM(High)IgD(Int) CD21(High)CD23(Low)CD1d(+)CD138(-). These cells, when isolated during the first peak of infection, stained positive for Annexin V and had increased caspase-3 enzyme activity. Elevated caspase-3 mRNA levels coincided with decreased mRNA levels of the anti-apoptotic Bcl-2 protein and BAFF receptor (BAFF-R), indicating the onset of apoptosis. Moreover, affected B cells became unresponsive to stimulation by BCR cross-linking with anti-IgM Fab fragments. In vivo, infection-induced loss of IgM(+) B cells coincided with the disappearance of protective variant-specific T-independent IgM responses, rendering the host rapidly susceptible to re-challenge with previously encountered parasites. Finally, using the well-established human diphtheria, tetanus, and B. pertussis (DTPa) vaccination model in mice, we show that T. brucei infections abrogate vaccine-induced protective responses to a non-related pathogen such as B. pertussis. Infections with T. brucei parasites result in the rapid loss of T-cell independent IgM(+)MZ B cells that are normally functioning as the primary immune barrier against blood-borne pathogens. In addition, ongoing trypanosome infections results in the rapid loss of B cell responsiveness and prevent the induction of protective memory responses. Finally, trypanosome infections disable the host's capacity to recall vaccine-induced memory responses against non-related pathogens. In particular, these last results call for detailed studies of the effect of HAT on memory recall responses in humans, prior to the planning of any mass vaccination campaign in HAT endemic areas.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Immunology and immunopathology of African trypanosomiasis

Major modifications of immune system have been observed in African trypanosomiasis. These immune reactions do not lead to protection and are also involved in immunopathology disorders. The major surface component (variable surface glycoprotein,VSG) is associated with escape to immune reactions, cytokine network dysfunctions and autoantibody production. Most of our knowledge result from experimental trypanosomiasis. Innate resistance elements have been characterised. In infected mice, VSG preferentially stimulates a Th 1-cell subset. A response of <FONT FACE=Symbol>gd</FONT> and CD8 T cells to trypanosome antigens was observed in trypanotolerant cattle. An increase in CD5 B cells, responsible for most serum IgM and production of autoantibodies has been noted in infected cattle. Macrophages play important roles in trypanosomiasis, in synergy with antibodies (phagocytosis) and by secreting various molecules (radicals, cytokines, prostaglandins,...). Trypanosomes are highly sensitive to TNF-alpha, reactive oxygen and nitrogen intermediates. TNF-alpha is also involved in cachexia. IFN-gamma acts as a parasite growth factor. These various elements contribute to immunosuppression. Trypanosomes have learnt to use immune mechanisms to its own profit. Recent data show the importance of alternative macrophage activation, including arginase induction. L-ornithine produced by host arginase is essential to parasite growth. All these data reflect the deep insight into the immune system realised by trypanosomes and might suggest interference therapeutic approaches.<br>Modificações importantes no sistema imune são observadas na tripanosomíase Africana. Essas reações imunológicas não protegem e estão envolvidas em distúrbios imunopatológicos. O principal componente de superfície (glicoproteína variante de superfície, VSG) está associado à evasão das respostas imune, às disfunções da rede de citocinas e à produção de autoanticorpos. Muitos de nossos conhecimentos resultam da tripanosomíase experimental. Componentes da imunidade inata estão sendo caracterizados. Em camundongos infectados, a VSG estimula preferencialmente células Th1. Uma resposta de <FONT FACE=Symbol>gd</FONT> e células T CD8 aos antígenos do tripanossoma foi observada em gado tripanotolerante. Um aumento em células B CD5, responsável por IgM sérica e produção de autoanticorpos, foi observado no gado infectado. Os macrófagos desempenham importantes funções na tripanosomíase, em sinergismo com anticorpos (fagocitose) e pela secreção de várias moléculas (radicais, citocinas, prostaglandinas). Tripanossomas são altamente sensíveis ao TNF-alfa, espécies reativas de oxigênio e nitrogênio. O TNF-alfa também está envolvido em caquexia. O IFN-gama atua como um fator de crescimento do parasita. Esses vários componentes contribuem para a imunossupressão. Os tripanossomas usam os mecanismos imunes para seu próprio benefício. Dados recentes mostram a importância da ativação alternativa de macrófagos, incluindo a indução pela arginase. A L-ornitina produzida pela arginase do hospedeiro é essencial para o crescimento do parasita. Todos esses dados mostram o envolvimento no sistema imune realizado pelos tripanossomas e sugerem a interferência de métodos terapêuticos