Identification of candidate infection genes from the model entomopathogenic nematode Heterorhabditis bacteriophora

Abstract

BackgroundDespite important progress in the field of innate immunity, our understanding of host immune responses to parasitic nematode infections lags behind that of responses to microbes. A limiting factor has been the obligate requirement for a vertebrate host which has hindered investigation of the parasitic nematode infective process. The nematode parasite Heterorhabditis bacteriophora offers great potential as a model to genetically dissect the process of infection. With its mutualistic Photorhabdus luminescens bacteria, H. bacteriophora invades multiple species of insects, which it kills and exploits as a food source for the development of several nematode generations. The ability to culture the life cycle of H. bacteriophora on plates growing the bacterial symbiont makes it a very exciting model of parasitic infection that can be used to unlock the molecular events occurring during infection of a host that are inaccessible using vertebrate hosts.ResultsTo profile the transcriptional response of an infective nematode during the early stage of infection, we performed next generation RNA sequencing on H. bacteriophora IJs incubated in Manduca sexta hemolymph plasma for 9 h. A subset of up-regulated and down-regulated genes were validated using qRT-PCR. Comparative analysis of the transcriptome with untreated controls found a number of differentially expressed genes (DEGs) which cover a number of different functional categories. A subset of DEGs is conserved across Clade V parasitic nematodes revealing an array of candidate parasitic genes.ConclusionsOur analysis reveals transcriptional changes in the regulation of a large number of genes, most of which have not been shown previously to play a role in the process of infection. A significant proportion of these genes are unique to parasitic nematodes, suggesting the identification of a group of parasitism factors within nematodes. Future studies using these candidates may provide functional insight into the process of nematode parasitism and also the molecular evolution of parasitism within nematodes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3468-6) contains supplementary material, which is available to authorized users.

A putative UDP-glycosyltransferase from Heterorhabditis bacteriophora suppresses antimicrobial peptide gene expression and factors related to ecdysone signaling

“…To further examine whether Hb-ugt-1 functions as a virulence factor, we performed a number of assays related to its expression and in vivo activity in the model host D. melanogaster . In agreement with the RNA sequencing assay that initially identified this glycosyltransferase 13 , Hb-ugt-1 was upregulated by H. bacteriophora infective juveniles (IJs) in response to hemolymph from multiple insect species, including D. melanogaster , though interestingly not in response to the nematode’s symbiotic bacterium Photorhabdus luminescens . A recombinant version of Hb-ugt-1 (r Hb-ugt-1 ) suppressed the upregulation of AMP gene expression following microinjection, as do total excreted-secreted (ES) products of H. bacteriophora 14 .…”

Bioactive Excreted/Secreted Products of Entomopathogenic Nematode Heterorhabditis bacteriophora Inhibit the Phenoloxidase Activity during the Infection

“…In some studies, hemolymph has been used to activate nematodes because it can be easily obtained in desirable volumes, especially from larger insect species [ 35 , 75 ]. However, insect homogenate is more suitable for studies that require the same chemical composition of activation material as that of natural hosts [ 31 ].…”

Transmission Success of Entomopathogenic Nematodes Used in Pest Control

“…The venom proteome of S. carpocapsae IJs was recently analyzed using mass spectrometry, highlighting the presence of 472 venom proteins including numerous proteases and protease inhibitors, as well as toxin-related proteins potentially linked to the suppression of host immune system [ 147 ]. In addition, the host immune response could be better understood with transcriptomic analyses following nematodes infection [ 186 , 187 , 188 ]. Genetic analyses, including sequencing, are particularly useful to better understand the diversity of nematodes [ 189 , 190 ] and their symbiotic bacteria [ 191 , 192 ], and to study their phylogenetic relationships [ 193 ].…”