Bx_Bm_transcriptomes
Comparative Transcriptomes Analysis of Two Pinewood Nematodes Bursaphelenchus xylophilus and Bursaphelenchus mucronatus by Deep-Sequencing Technology
Summary: Bursaphelenchus xylophilus and B. mucronatus are migratory endoparasitic nematodes and ubiquity in pine forests of North America and Eurasia respectively.  Both species are very similar in morphological, biological and ecological characteristics, but different in pathogenicity and invasiveness. To have a comprehensive understanding of similarities and differences of the two nematodes in molecular characterization, transcriptomes of the two nematodes were analyzed and compared.   Transcripts of each nematode from mixed stages in propagative cycles were obtained by Illumina/Solexa deep-sequencing technology. A total of 26,796 and 26,069 unigenes (>150bp) were obtained from B. xylophilus and B. mucronatus respectively. Of which 54.5% and 50.9% showed homology to sequences of known proteins from the GenBank nr database. Comparison of the two transcriptomes showed that the similarity of both nematodesÃ¢Â€Â™ transcripts was more than 80%. No obvious difference was observed on functional level between the two nematodes transcriptomes by GO classification, or COG classification and KO analysis. Except previous reported genes, such as genes encoding plant cell-wall-degrading CAZymes (mainly cellulases and pectate lyases), expansin-like proteins and other secreted proteins, putative novel candidatess of parasitism genes encoding ancylostoma-secreted proteins (ASP) were detected, with four unigenes in B. xylophilus and one unigenes in B. mucronatus. This is the first report of genes in plant parasitic nematode encoding proteins ortholog to ASPs of animal-parasitic nematodes. Moreover, genes encoding fungal cell-wall-degrading CAZymes (mainly chitin and beta-1,3 endoglucanase) were also refreshed. Furthermore, it was found that in the two nematode transcriptomes enzymes participating in xenobiotic metalism and pinene degradation were comparatively rich, mainly including cytochromes P450 proteins (especially cyp-33 family member), Glutathione S-transferases, UDP-glucuronosyl transferases, short chain dehydrogenase/reductases, aldehyde dehydrogenases and antioxidants. The numbers of CYPs and GSTs in the two nematodes were significantly richer than those in knot-root nematode Meloidogyne incognita. These genes perhaps play important roles on parasitic adaptation to pine hosts for the nematodes.   The results of this study indicate that the two sister species B. xylophilus and B. mucronatus are not only very similar in morphological, biological and ecological traits, but also very similar in molecular characterization. They have similar molecular mechanisms of adaptation to parasitize in pine hosts, including parasitism and metabolism adaptation, which was different from those in the sedentary parasitic nematodes.  Parasitic adaptation of the two nematodes is interesting for further research.  Overall Design: To have a comprehensive understanding of similarities and differences of the two PWN (pine-wood nematode) in molecular characterization, transcriptomes from mixed stages of B. xylophilus and B. mucronatus were obtained by Illumina deep-sequencing technology and compared.
Bursaphelenchus xylophilus and Bursaphelenchus mucronatus are migratory endoparasitic nematodes that live in pine trees. To gain insight into their molecular similarities and differences, transcriptomes of the two nematodes were analysed. A total of 23,765 and 21,782 contigs (> 300 bp) were obtained from B. xylophilus and B. mucronatus, respectively. More than 80% of the contigs could map to each other's transcriptome reciprocally. A total of 23,467 and 21,370 Open Reading Frames were predicted, respectively. Besides those known parasitism-related proteins, six new venom allergen-like proteins (VAPs) were found, which were not homologous to known VAPs. Enzymes involved in xenobiotic biodegradation were abundant in the two transcriptomes based on KEGG functional annotation. Metabolism of xenobiotics by cytochrome P450 comprised the main detoxification pathways. The mRNA expression levels of detoxification genes in nematodes living in the host were higher than those in nematodes feeding on fungus. However, there were fewer enzymes involved in the a-pinene degradation. Our results indicate that the two pinewood nematodes have evolved similar molecular mechanisms to adapt to life on pine hosts.