Dataset Information

Assessing the Pathogenicity of Two Bacteria Isolated from the Entomopathogenic Nematode Heterorhabditis indica against Galleria mellonella and Some Pest Insects.

ABSTRACT: The entomopathogenic nematodes Heterorhabditis are parasites of insects and are associated with mutualist symbiosis enterobacteria of the genus Photorhabdus; these bacteria are lethal to their host insects. Heterorhabditis indica MOR03 was isolated from sugarcane soil in Morelos state, Mexico. The molecular identification of the nematode was confirmed using sequences of the ITS1-5.8S-ITS2 region and the D2/D3 expansion segment of the 28S rRNA gene. In addition, two bacteria HIM3 and NA04 strains were isolated from the entomopathogenic nematode. The genomes of both bacteria were sequenced and assembled de novo. Phylogenetic analysis was confirmed by concatenated gene sequence datasets as Photorhabdus luminescens HIM3 (16S rRNA, 23S rRNA, dnaN, gyrA, and gyrB genes) and Pseudomonas aeruginosa NA04 (16S rRNA, 23S rRNA and gyrB genes). H. indica MOR03 infects Galleria mellonella, Tenebrio molitor, Heliothis subflexa, and Diatraea magnifactella larvae with LC50 values of 1.4, 23.5, 13.7, and 21.7 IJs/cm², respectively, at 48 h. These bacteria are pathogenic to various insects and have high injectable insecticide activity at 24 h.

SUBMITTER: Salgado-Morales R

PROVIDER: S-EPMC6468454 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Assessing the Pathogenicity of Two Bacteria Isolated from the Entomopathogenic Nematode Heterorhabditis indica against Galleria mellonella and Some Pest Insects.

Salgado-Morales Rosalba R Martínez-Ocampo Fernando F Obregón-Barboza Verónica V Vilchis-Martínez Kathia K Jiménez-Pérez Alfredo A Dantán-González Edgar E

Insects 20190326 3

The entomopathogenic nematodes Heterorhabditis are parasites of insects and are associated with mutualist symbiosis enterobacteria of the genus Photorhabdus; these bacteria are lethal to their host insects. Heterorhabditis indica MOR03 was isolated from sugarcane soil in Morelos state, Mexico. The molecular identification of the nematode was confirmed using sequences of the ITS1-5.8S-ITS2 region and the D2/D3 expansion segment of the 28S rRNA gene. In addition, two bacteria ...[more]

PMID: 30917525

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Project description:The entomopathogenic nematode Heterorhabditis bacteriophora and its symbiotic bacterium, Photorhabdus luminescens, are important biological control agents of insect pests. This nematode-bacterium-insect association represents an emerging tripartite model for research on mutualistic and parasitic symbioses. Elucidation of mechanisms underlying these biological processes may serve as a foundation for improving the biological control potential of the nematode-bacterium complex. This large-scale expressed sequence tag (EST) analysis effort enables gene discovery and development of microsatellite markers. These ESTs will also aid in the annotation of the upcoming complete genome sequence of H. bacteriophora.A total of 31,485 high quality ESTs were generated from cDNA libraries of the adult H. bacteriophora TTO1 strain. Cluster analysis revealed the presence of 3,051 contigs and 7,835 singletons, representing 10,886 distinct EST sequences. About 72% of the distinct EST sequences had significant matches (E value < 1e-5) to proteins in GenBank's non-redundant (nr) and Wormpep190 databases. We have identified 12 ESTs corresponding to 8 genes potentially involved in RNA interference, 22 ESTs corresponding to 14 genes potentially involved in dauer-related processes, and 51 ESTs corresponding to 27 genes potentially involved in defense and stress responses. Comparison to ESTs and proteins of free-living nematodes led to the identification of 554 parasitic nematode-specific ESTs in H. bacteriophora, among which are those encoding F-box-like/WD-repeat protein theromacin, Bax inhibitor-1-like protein, and PAZ domain containing protein. Gene Ontology terms were assigned to 6,685 of the 10,886 ESTs. A total of 168 microsatellite loci were identified with primers designable for 141 loci.A total of 10,886 distinct EST sequences were identified from adult H. bacteriophora cDNA libraries. BLAST searches revealed ESTs potentially involved in parasitism, RNA interference, defense responses, stress responses, and dauer-related processes. The putative microsatellite markers identified in H. bacteriophora ESTs will enable genetic mapping and population genetic studies. These genomic resources provide the material base necessary for genome annotation, microarray development, and in-depth gene functional analysis.

Project description:Despite 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.To 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.Our 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.

Project description:BackgroundNematodes are the most numerous animals in the soil. Insect parasitic nematodes of the genus Heterorhabditis are capable of selectively seeking, infecting and killing their insect-hosts in the soil. The infective juvenile (IJ) stage of the Heterorhabditis nematodes is analogous to Caenorhabditis elegans dauer juvenile stage, which remains in 'arrested development' till it finds and infects a new insect-host in the soil. H. indica is the most prevalent species of Heterorhabditis in India. To understand the genes and molecular processes that govern the biology of the IJ stage, and to create a resource to facilitate functional genomics and genetic exploration, we sequenced the transcriptome of H. indica IJs.ResultsThe de-novo sequence assembly using Velvet-Oases pipeline resulted in 13,593 unique transcripts at N50 of 1,371 bp, of which 53 % were annotated by blastx. H. indica transcripts showed higher orthology with parasitic nematodes as compared to free living nematodes. In-silico expression analysis showed 30 % of transcripts expressing with ≥100 FPKM value. All the four canonical dauer formation pathways like cGMP-PKG, insulin, dafachronic acid and TGF-β were active in the IJ stage. Several other signaling pathways were highly represented in the transcriptome. Twenty-four orthologs of C. elegans RNAi pathway effector genes were discovered in H. indica, including nrde-3 that is reported for the first time in any of the parasitic nematodes. An ortholog of C. elegans tol-1 was also identified. Further, 272 kinases belonging to 137 groups, and several previously unidentified members of important gene classes were identified.ConclusionsWe generated high-quality transcriptome sequence data from H. indica IJs for the first time. The transcripts showed high similarity with the parasitic nematodes, M. hapla, and A. suum as opposed to C. elegans, a species to which H. indica is more closely related. The high representation of transcripts from several signaling pathways in the IJs indicates that despite being a developmentally arrested stage; IJs are a hotbed of signaling and are actively interacting with their environment.

Dataset Information

Assessing the Pathogenicity of Two Bacteria Isolated from the Entomopathogenic Nematode Heterorhabditis indica against Galleria mellonella and Some Pest Insects.

Publications

Assessing the Pathogenicity of Two Bacteria Isolated from the Entomopathogenic Nematode <i>Heterorhabditis indica</i> against <i>Galleria mellonella</i> and Some Pest Insects.

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