title: A transcriptomic insight into the infective juvenile stage of the insect parasitic nematode, Heterorhabditis indica.
abstract: BACKGROUND
  Nematodes 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  We 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.
authors.affiliation: Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India. vssomvanshi@iari.res.in.
authors.forename: Vishal S
authors.initials: VS
authors.lastname: Somvanshi
authors.affiliation: Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India. shachigahoimbi@gmail.com.
authors.forename: Shachi
authors.initials: S
authors.lastname: Gahoi
authors.affiliation: Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India. prakashbanakar@gmail.com.
authors.forename: Prakash
authors.initials: P
authors.lastname: Banakar
authors.affiliation: Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India. praasu@gmail.com.
authors.forename: Prasoon Kumar
authors.initials: PK
authors.lastname: Thakur
authors.affiliation: Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India. mukeshbioinformat@gmail.com.
authors.forename: Mukesh
authors.initials: M
authors.lastname: Kumar
authors.affiliation: Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India. mani.sajnani@gmail.com.
authors.forename: Manisha
authors.initials: M
authors.lastname: Sajnani
authors.affiliation: Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India. priyatamapandey@gmail.com.
authors.forename: Priyatama
authors.initials: P
authors.lastname: Pandey
authors.affiliation: Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India. umarao@iari.res.in.
authors.forename: Uma
authors.initials: U
authors.lastname: Rao
mesh_terms: D000818:Animals; D063990:Gene Ontology; D017238:Genes, Helminth; D007313:Insecta / Q000469:parasitology*; D008018:Life Cycle Stages; D053858:Metabolic Networks and Pathways; D009348:Nematoda / Q000235:genetics*; D034622:RNA Interference; D015398:Signal Transduction; D059467:Transcriptome