Suchergebnisse

The pinewood nematode (PWN), Bursaphelenchus xylophilus, is a quarantine organism in the European Union and the causal agent of pine wilt disease (PWD), a serious threat to pine forests worldwide, leading to rapid decline and death. In Europe, this invasive pest was first reported in Portugal in 1999, on Pinus pinaster. Due to its economic importance and worldwide distribution, an enormous effort has been devoted to research on B. xylophilus and PWD. However, relating the presence and abundance of this pest with actual forest decline and mortality is not straightforward. In the present work, we assess the interaction between B. xylophilus populations and pine decline at the tree and landscape level. To test this, we determined PWN population densities from different sections of healthy and declining P. pinaster – considered very susceptible to PWN – and P. pinea – considered resistant, in two consecutive years. The studied site was Herdade da Apostiça (Sesimbra, Portugal), a 4 thousand ha forest that exhibits areas of moderate to severe decline. An approximate 500 m long transect was set in four different areas of the experimental site, along which healthy and declining P. pinaster trees were randomly selected. Wood samples from lower (DBH), middle (M) and upper (T) sections of trees were retrieved whenever possible, and kept in individual plastic bags to avoid cross contamination. Twigs from the canopy were also sampled. When present, samples from P. pinea were collected as well. Nematodes were extracted from wood material using a modified Baermann tray method, and counted under a stereoscopic microscope. With only few exceptions, M and T sections consistently displayed the lowest PWN densities, although samples collected at breast height (DBH) also had relatively low numbers of B. xylophilus. On the other hand, twigs had the highest numbers of nematodes in all areas. Surprisingly, nematodes were extracted from the canopy of apparently healthy P. pinaster trees, including the PWN, although in low densities. Expectedly, areas with no visible tree decline had low population densities of B. xylophilus, and declining trees tended to present higher numbers. P. pinea samples were mostly free of the PWN. To further understand the complex dynamics shaping pine forest decline caused by the PWN, more sampling will be carried out in the upcoming months. This will allow us to build predictive models on the spread and damage of PWD.

Background Schistosomiasis is one of the most prevalent parasitic diseases worldwide and is a public health problem. Schistosoma mansoni is the most widespread species responsible for schistosomiasis in the Americas, Middle East and Africa. Adult female worms (mated to males) release eggs in the hepatic portal vasculature and are the principal cause of morbidity. Comparative separate transcriptomes of female and male adult worms were previously assessed with using microarrays and Serial Analysis of Gene Expression (SAGE), thus limiting the possibility of finding novel genes. Moreover, the egg transcriptome was analyzed only once with limited bacterially cloned cDNA libraries. Methodology/Principal findings To compare the gene expression of S. mansoni eggs, females, and males, we performed RNA-Seq on these three parasite forms using 454/Roche technology and reconstructed the transcriptome using Trinity de novo assembly. The resulting contigs were mapped to the genome and were cross-referenced with predicted Smp genes and H3K4me3 ChIP-Seq public data. For the first time, we obtained separate, unbiased gene expression profiles for S. mansoni eggs and female and male adult worms, identifying enriched biological processes and specific enriched functions for each of the three parasite forms. Transcripts with no match to predicted genes were analyzed for their protein-coding potential and the presence of an encoded conserved protein domain. A set of 232 novel protein-coding genes with putative functions related to reproduction, metabolism, and cell biogenesis was detected, which contributes to the understanding of parasite biology. Conclusions/Significance Large-scale RNA-Seq analysis using de novo assembly associated with genome-wide information for histone marks in the vicinity of gene models constitutes a new approach to transcriptome analysis that has not yet been explored in schistosomes. Importantly, all data have been consolidated into a UCSC Genome Browser search-and download-tool (http://schistosoma.usp.br/). This database provides new ways to explore the schistosome genome and transcriptome and will facilitate molecular research on this important parasite. ; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [2010/51687-8]; European Union's Seventh Framework Programme [602080]; FAPESP; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Brasil ; This work was supported by a grant from Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP grant number 2010/51687-8) to SVA and in part by a grant from the European Union's Seventh Framework Programme under grant agreement no. 602080. LA, MSA, FB, KCPO, GTA were supported by fellowships from FAPESP. SVA, JCS and RDM received established investigator fellowship awards from the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Brasil. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.