Transcriptome of a specialized extra‐embryonic cell, teratocyte, and its host immunosuppressive role revealed by ex vivo RNA interference

Abstract

The specialized wasp cells teratocytes (TCs) are derived from the embryonic serosal membrane of some parasitic hymenopteran insects. As a parasitic factor, TCs are multifunctional in host regulation, such as host nutritional deprivation, immunosuppression and developmental arrest; however, little is understood about their genetic constituents. The present study provides a comprehensive view of the genes expressed by TCs through a transcriptome analysis based on RNA sequencing technology. The assembled 34 686 contigs (>200 base pairs) were annotated into different functional categories, indicating a distinct distribution in gene transcripts compared with those of haemocytes and fat body. The TC transcriptome contained components of insulin signalling and biosyntheses of juvenile hormone and 20-hydroxyecdysone. TCs also expressed various groups of digestive enzymes, indicating that they have nutritional role for the growing parasitoid larvae in parasitism. Furthermore, through this transcriptome analysis two kinds of immunosuppressive serine protease inhibitors (serpins) and Rho GTPase-activating proteins (RhoGAPs) were annotated. To determine the biological functions of these factors, we devised ex vivo RNA interference (RNAi) by conducting knockdown of gene expression in in vitro-cultured TCs followed by injection of the treated TCs to test insects. Ex vivo RNAi revealed that some serpins and RhoGAPs expressed in TCs inhibited host cellular immunity. This study reports a transcriptome of the unique TC animal cell and its immunosuppressive genetic factors using ex vivo RNAi technology.

Regulation of the Larval Transcriptome of Diatraea saccharalis (Lepidoptera: Crambidae) by Maternal and Other Factors of the Parasitoid Cotesia flavipes (Hymenoptera: Braconidae)

“…Research to identify the bioactive molecules that parasitoids use to regulate their hosts and expand our understanding of the regulation of host gene expression has intensified, with next-generation sequencing techniques and bioinformatic tools supporting systemic analyses (Fang et al, 2010; Etebari et al, 2011; Provost et al, 2011; Laurino et al, 2016). Genomic analyses are elucidating the organization of the integrated and encapsidated forms of the PDV genome (Chevignon et al, 2014), and transcriptome analyses are depicting the profile of viral and host gene expression in parasitized hosts (Bitra et al, 2011; Provost et al, 2011; Dorémus et al, 2014; Ali et al, 2015). Integrative analyses have identified bioactive molecules present in maternal factors injected by the parasitoid (Laurino et al, 2016; Liu et al, 2017).…”

De novo transcriptome sequencing and analysis of Coccinella septempunctata L. in non-diapause, diapause and diapause-terminated states to identify diapause-associated genes

“…For organisms without reference genomes, de novo transcriptome sequencing can not only produce genetic information for the species but also be used to predict possible non-coding RNA [ 46 , 47 ]. Transcriptome sequencing of insect samples obtained under different growing conditions or from different habitats or species not only generates functional gene information and reveals differentially expressed genes but also provides the abundance of expressed transcripts, the loci where transcription occurs, transcript SNPs and other important information [ 48 – 51 ]. We conducted research on diapause in C. septempunctata L. based on the results of other insect studies [ 52 ].…”

Cotesia vestalis teratocytes express a diversity of genes and exhibit novel immune functions in parasitism

“…Endoparasitic braconids like C. vestalis parasitize hosts by injecting eggs, PDVs and venom, which is followed by the release of teratocytes when wasp eggs hatch 1 . Previous studies establish that PDVs and venoms have important functions in parasitism but the roles of teratocytes are less understood with only two transcriptome data sets reported and only a small number of studies that have investigated the function of specific teratocyte genes 16 18 28 33 34 . Here we provide a new transcriptome data set for C. vestalis teratocytes that were collected directly from hosts at different times post-parasitism.…”

“…Two recent studies report transcriptome data for teratocytes from Microplitis demolitor and Cotesia plutellae that were produced in primary culture 33 34 . However, it is also possible that the host environment affects teratocyte gene expression.…”