Concurrent transcriptional profiling of Dirofilaria immitis and its Wolbachia endosymbiont throughout the nematode life cycle reveals coordinated gene expression

Abstract

BackgroundDirofilaria immitis, or canine heartworm, is a filarial nematode parasite that infects dogs and other mammals worldwide. Current disease control relies on regular administration of anthelmintic preventives, however, relatively poor compliance and evidence of developing drug resistance could warrant alternative measures against D. immitis and related human filarial infections be taken. As with many other filarial nematodes, D. immitis contains Wolbachia, an obligate bacterial endosymbiont thought to be involved in providing certain critical metabolites to the nematode. Correlations between nematode and Wolbachia transcriptomes during development have not been examined. Therefore, we detailed the developmental transcriptome of both D. immitis and its Wolbachia (wDi) in order to gain a better understanding of parasite-endosymbiont interactions throughout the nematode life cycle.ResultsOver 215 million single-end 50 bp reads were generated from total RNA from D. immitis adult males and females, microfilariae (mf) and third and fourth-stage larvae (L3 and L4). We critically evaluated the transcriptomes of the various life cycle stages to reveal sex-biased transcriptional patterns, as well as transcriptional differences between larval stages that may be involved in larval maturation. Hierarchical clustering revealed both D. immitis and wDi transcriptional activity in the L3 stage is clearly distinct from other life cycle stages. Interestingly, a large proportion of both D. immitis and wDi genes display microfilarial-biased transcriptional patterns. Concurrent transcriptome sequencing identified potential molecular interactions between parasite and endosymbiont that are more prominent during certain life cycle stages. In support of metabolite provisioning between filarial nematodes and Wolbachia, the synthesis of the critical metabolite, heme, by wDi appears to be synchronized in a stage-specific manner (mf-specific) with the production of heme-binding proteins in D. immitis.ConclusionsOur integrated transcriptomic study has highlighted interesting correlations between Wolbachia and D. immitis transcription throughout the life cycle and provided a resource that may be used for the development of novel intervention strategies, not only for the treatment and prevention of D. immitis infections, but of other closely related human parasites as well.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-1041) contains supplementary material, which is available to authorized users.

Tissue-specific transcriptomics and proteomics of a filarial nematode and its Wolbachia endosymbiont

“…Inclusion of recently published whole-worm adult male (AM) and adult female (AF) transcriptomes [ 16 ] in the cluster analysis of the D. immitis tissue transcriptomes revealed the adult worm transcriptional profiles were most similar to their respective sex organs (testis or uterus) (Fig. 1a ).…”

“…1 Global comparison of D.immitis tissue transcriptomes. Hierarchical clustering reveals similarities between the transcriptional profiles of D. immitis ( a ) and w Di ( b ) from different tissues ( FH female head, FBW female body wall, FU female uterus, MT male testis, FI female intestine, MI male intestine, MBW male body wall) and whole adult worms ( AF adult female, AM adult male, from [ 16 ], shown in red ) …”

“…While increasingly more filarial nematode genome sequences (and their respective Wolbachia counterparts) are becoming readily available, other ‘omics’ approaches (transcriptomics/proteomics) are needed to provide more detailed functional information. Previous transcriptomics (RNA-seq) studies have analyzed gene expression throughout the filarial nematode life cycle [ 15 , 16 ]. Nevertheless, these whole organism approaches do not provide spatial resolution of gene expression, which can be gained by tissue specific gene expression profiling.…”

Lessons from the genomes and transcriptomes of filarial nematodes

“…Such studies have been completed in D. immitis, O. ochengi , and B. malayi [26, 29, 30] [Manuscript under review at PLoS NTD]. In all studies, the transcripts for the chaperonin and heat shock proteins including GroEL, GroES, and DnaK were among the most highly expressed.…”

Perusal of parasitic nematode ‘omics in the post-genomic era

“…While most D. immitis miRNAs are conserved with B. malayi , 13 novel miRNAs have been identified [55]. Biosynthesis of heme by the Wolbachia endosymbiont predominantly occurs in microfilariae and corresponds with expression of D. immitis heme-binding proteins [56]. Studies of D. immitis ESP [57], as well as somatic and surface proteins [58], have identified multiple proteins involved in host-parasite interactions.…”