Wolbachia Interferes with Ferritin Expression and Iron Metabolism in Insects

Wolbachia is an intracellular bacterium generally described as being a facultative reproductive parasite. However, Wolbachia is necessary for oogenesis completion in the wasp Asobara tabida. This dependence has evolved recently as a result of interference with apoptosis during oogenesis. Through comparative transcriptomics between symbiotic and aposymbiotic individuals, we observed a differential expression of ferritin, which forms a complex involved in iron storage. Iron is an essential element that is in limited supply in the cell. However, it is also a highly toxic precursor of Reactive Oxygen Species (ROS). Ferritin has also been shown to play a key role in host–pathogen interactions. Measuring ferritin by quantitative RT-PCR, we confirmed that ferritin was upregulated in aposymbiotic compared to symbiotic individuals. Manipulating the iron content in the diet, we showed that iron overload markedly affected wasp development and induced apoptotic processes during oogenesis in A. tabida, suggesting that the regulation of iron homeostasis may also be related to the obligate dependence of the wasp. Finally, we demonstrated that iron metabolism is influenced by the presence of Wolbachia not only in the obligate mutualism with A. tabida, but also in facultative parasitism involving Drosophila simulans and in Aedes aegypti cells. In these latter cases, the expression of Wolbachia bacterioferritin was also increased in the presence of iron, showing that Wolbachia responds to the concentration of iron. Our results indicate that Wolbachia may generally interfere with iron metabolism. The high affinity of Wolbachia for iron might be due to physiological requirement of the bacterium, but it could also be what allows the symbiont to persist in the organism by reducing the labile iron concentration, thus protecting the cell from oxidative stress and apoptosis. These findings also reinforce the idea that pathogenic, parasitic and mutualistic intracellular bacteria all use the same molecular mechanisms to survive and replicate within host cells. By impacting the general physiology of the host, the presence of a symbiont may select for host compensatory mechanisms, which extends the possible consequences of persistent endosymbiont on the evolution of their hosts

Host gene response to endosymbiont and pathogen in the cereal weevil Sitophilus oryzae

Background: Insects thriving on nutritionally poor habitats have integrated mutualistic intracellular symbiotic bacteria (endosymbionts) in a bacteria-bearing tissue (the bacteriome) that isolates the endosymbionts and protects them against a host systemic immune response. Whilst the metabolic and physiological features of long-term insect associations have been investigated in detail over the past decades, cellular and immune regulations that determine the host response to endosymbionts and pathogens have attracted interest more recently. Results: To investigate bacteriome cellular specificities and weevil immune responses to bacteria, we have constructed and sequenced 7 cDNA libraries from Sitophilus oryzae whole larvae and bacteriomes. Bioinformatic analysis of 26,886 ESTs led to the generation of 8,941 weevil unigenes. Based on in silico analysis and on the examination of genes involved in the cellular pathways of potential interest to intracellular symbiosis (i.e. cell growth and apoptosis, autophagy, immunity), we have selected and analyzed 29 genes using qRT-PCR, taking into consideration bacteriome specificity and symbiosis impact on the host response to pathogens. We show that the bacteriome tissue accumulates transcripts from genes involved in cellular development and survival, such as the apoptotic inhibitors iap2 and iap3, and endosomal fusion an

Identification of the Weevil immune genes and their expression in the bacteriome tissue

<p>Abstract</p> <p>Background</p> <p>Persistent infections with mutualistic intracellular bacteria (endosymbionts) are well represented in insects and are considered to be a driving force in evolution. However, while pathogenic relationships have been well studied over the last decades very little is known about the recognition of the endosymbionts by the host immune system and the mechanism that limits their infection to the bacteria-bearing host tissue (the bacteriome).</p> <p>Results</p> <p>To study bacteriome immune specificity, we first identified immune-relevant genes of the weevil <it>Sitophilus zeamais </it>by using suppressive subtractive hybridization (SSH) and then analyzed their full-length coding sequences obtained by RACE-PCR experiments. We then measured immune gene expression in the bacteriome, and in the aposymbiotic larvae following <it>S. zeamais </it>primary endosymbiont (SZPE) injection into the hemolymph, in order to consider the questions of bacteriome immune specificity and the insect humoral response to symbionts. We show that larval challenge with the endosymbiont results in a significant induction of antibacterial peptide genes, providing evidence that, outside the bacteriome, SZPE are recognized as microbial intruders by the host. In the bacteriome, gene expression analysis shows the overexpression of one antibacterial peptide from the <it>coleoptericin </it>family and, intriguingly, homologs to genes described as immune modulators (that is, <it>PGRP-LB, Tollip</it>) were also shown to be highly expressed in the bacteriome.</p> <p>Conclusion</p> <p>The current data provide the first description of immune gene expression in the insect bacteriome. Compared with the insect humoral response to SZPE, the bacteriome expresses few genes among those investigated in this work. This local immune gene expression may help to maintain the endosymbiont in the bacteriome and prevent its invasion into insect tissues. Further investigations of the <it>coleoptericin</it>, the <it>PGRP </it>and the <it>Tollip </it>genes should elucidate the role of the host immune system in the maintenance and regulation of endosymbiosis.</p

Repository/R-Forge/DateTimeStamp 2012-12-11 16:03:18

Suggests ade4, segmented Description Exploratory data analysis and data visualization for biological sequence (DNA and protein) data. Include also utilities for sequence data management under the ACNUC system. License GPL (&gt; = 2

A transcriptomic dataset for investigating the Arabidopsis Unfolded Protein Response under chronic, proteotoxic endoplasmic reticulum stress

International audienceThe Unfolded Protein Response (UPR) is a retrograde, ER-to-nucleus, signalling pathway which is conserved across kingdoms. In plants, it contributes to development, reproduction, immunity and tolerance to abiotic stress. This RNA sequencing (RNA-seq) dataset was produced from 14-day-old Arabidopsis thaliana seedlings challenged by tunicamycin (Tm), an antibiotic inhibiting Asn-linked glycosylation in the endoplasmic reticulum (ER), causing an ER stress and eventually activating the UPR. Wild-type (WT) and a double mutant deficient for two main actors of the UPR (INOSITOL-REQUIRING ENZYME 1A and INOSITOL-REQUIRING ENZYME 1B) were used as genetic backgrounds in our experimental setup, allowing to distinguish among differentially-expressed genes (DEGs) which ones are dependent on or independent on IRE1s. Also, shoots and roots were harvested separately to determine organ-specific transcriptomic responses to Tm. Library and sequencing were performed using DNBseq™ technology by the Beijing Genomics Institute. Reads were mapped and quantified against the Arabidopsis genome. Differentially-expressed genes were identified using Rflomics upon filtering and normalization by the Trimmed Mean of M-value (TMM) method. While the genotype effect was weak under mock conditions (with a total of 182 DEGs in shoots and 195 DEGs in roots), the tunicamycin effect on each genotype was characterized by several hundred of DEGs in both shoots and roots. Among these genes, 872 and 563 genes were statistically up- and down-regulated in the shoot tissues of the double mutant when compared to those of WT, respectively. In roots of Tm-challenged seedlings, 425 and 439 genes were significantly up- and down-regulated in mutants with respect to WT. We believe that our dataset could be reused for investigating any biological questions linked to ER homeostasis and its role in plant physiology

Are there common host functions involved in insect symbioses ? A comparative transcriptomic approach

International audienc

Do variable compensatory mechanisms explain the polymorphism of the dependence phenotype in the Asobara tabida-wolbachia association?

International audienceWolbachia are symbiotic intracellular bacteria, which are classified as reproductive parasites. Although generally facultative, Wolbachia is necessary for Asobara tabida (Hymenoptera), because aposymbiotic females do not produce any offspring. Interestingly, the ovarian phenotype of aposymbiotic females is variable: some females do not produce any eggs, whereas others do produce some eggs, but these are aborted. Here, we show that the ovarian phenotype of aposymbiotic females is highly polymorphic within populations, although dependence remains complete in both cases. We also identified some lines in which aposymbiotic females were able to produce a very few viable offspring, further extending the range of variation observed. These results suggest that various factors actively maintain polymorphism. We demonstrated that Wolbachia is necessary to trigger oogenetic processes, but that the ovarian phenotype was determined by the host only. Phenotypic variation was also correlated with the differential expression of genes controlling iron homeostasis and oxidative stress, which are potentially involved in the evolution of dependence. This suggests that variation in the ovarian phenotype could reflect selection for different levels of compensatory mechanisms in response to Wolbachia infection, and that polymorphism is maintained through selection on different antagonist traits influenced by oxidative stress

RFLOMICS: R package and Shiny interface for Integrative analysis of omics data

International audienceThe acquisition of multi-omics data in the context of complex experimental design is a widely used practice to identify entities and decipher the biological processes they are involved. The investigation of each omics layer is a good first step to explore and extract relevant biological variability. The statistical integration could then be restrained to pertinent omics levels and features. Such analysis of heterogeneous data remains a technical challenge with the needs of expertise methods and parameters to take into account data specificity. Furthermore, applying different statistical methods from several tools is also a technical challenge in term of data management. In this context, we developed RFLOMICS, an R package with a shiny interface, to ensure the reproducibility of analysis, with a guided and comprehensive analysis and visualization of data in a framework which can manage several omics-data and analysis results. RFLOMICS currently supports up to three types of omics (RNAseq, proteomics, and metabolomics), and can deal with multi-factorial experiments (up to 3 biological factors). It includes methods chosen based on expert feedback. This application is divided into three key steps. The first step allows the user to import the experimental design file and abundance matrix for each dataset (read counts for RNA-Seq, signal intensity for metabolomics and proteomics), and set up the statistical model and contrasts associated to the biological issues. The second step is to perform a full analysis for each dataset, which includes : i- quality control to check for batch effects or identify outlier samples that can be removed, ii- filtering and normalization of RNA-Seq data, or transformation of prot/meta data, iii- differential expression analysis using edgeR for RNA- Seq and limma for prot/meta data, iv- co-expression analysis using coseq, and finally, v- functional enrichment analysis. The third step is to integrate selected omics layers using the unsupervised methods proposed by MOFA. All the results as well as the raw data, and all information necessary for reproducibility of analysis are managed and stored thanks to the MultiAssayExperiment object. An HTML report can be generated, summarizing all analysis steps, using rmarkdown R package. RFLOMICS provides the same framework that allows the user to perform the analysis of multi-omics project from A to Z, taking into account the complexity of the design. It guarantees the relevance of the used methods, and ensures the reproducibility of the analysis. The interface offers an interesting flexibility between the visualization of the results and the data manipulation (filtering, parameter setting). Future development will include the implementation of supervised integration methods, and a docker image to facilitate deployment