A neuropeptide modulates sensory perception in the entomopathogenic nematode Steinernema carpocapsae

Abstract

Entomopathogenic nematodes (EPNs) employ a sophisticated chemosensory apparatus to detect potential hosts. Understanding the molecular basis of relevant host-finding behaviours could facilitate improved EPN biocontrol approaches, and could lend insight to similar behaviours in economically important mammalian parasites. FMRFamide-like peptides are enriched and conserved across the Phylum Nematoda, and have been linked with motor and sensory function, including dispersal and aggregating behaviours in the free living nematode Caenorhabditis elegans. The RNA interference (RNAi) pathway of Steinernema carpocapsae was characterised in silico, and employed to knockdown the expression of the FMRFamide-like peptide 21 (GLGPRPLRFamide) gene (flp-21) in S. carpocapsae infective juveniles; a first instance of RNAi in this genus, and a first in an infective juvenile of any EPN species. Our data show that 5 mg/ml dsRNA and 50 mM serotonin triggers statistically significant flp-21 knockdown (-84%***) over a 48 h timecourse, which inhibits host-finding (chemosensory), dispersal, hyperactive nictation and jumping behaviours. However, whilst 1 mg/ml dsRNA and 50 mM serotonin also triggers statistically significant flp-21 knockdown (-51%**) over a 48 h timecourse, it does not trigger the null sensory phenotypes; statistically significant target knockdown can still lead to false negative results, necessitating appropriate experimental design. SPME GC-MS volatile profiles of two EPN hosts, Galleria mellonella and Tenebrio molitor reveal an array of shared and unique compounds; these differences had no impact on null flp-21 RNAi phenotypes for the behaviours assayed. Localisation of flp-21 / FLP-21 to paired anterior neurons by whole mount in situ hybridisation and immunocytochemistry corroborates the RNAi data, further suggesting a role in sensory modulation. These data can underpin efforts to study these behaviours in other economically important parasites, and could facilitate molecular approaches to EPN strain improvement for biocontrol.

Transcriptional signatures of invasiveness in Meloidogyne incognita populations from sub-Saharan Africa

“…This corroborates previous observations of flp gene enrichment within the infective juvenile stage of many parasitic nematode species, and a role in the behavioural diversification of these stages (Lee et al, 2017). Indeed, our own work demonstrates similar associations between neuropeptidergic genes and the host-finding behaviour of S. carpocapsae (Warnock et al, 2018;Morris et al, 2017). Four putative neuropeptide G-Protein Coupled Receptor (GPCR) genes were also found to associate with M. incognita invasiveness, along with seven ion channel genes, two innexin genes, an acetylcholinesterase and a predicted odr-8 peptidase homologue ( Figure 2C).…”

Host seeking parasitic nematodes use specific odors to assess host resources

“…mellonella hosts 10, 11, 19 . However, one of our controls–SPME-GC-MS experiments examining the odors emitted by the pine chips used as packing material for G .…”

Simultaneous RNAi Knockdown of Three FMRFamide-Like Peptide Genes, Mi-flp1, Mi-flp12, and Mi-flp18 Provides Resistance to Root-Knot Nematode, Meloidogyne incognita

“…Thus, FLPs interference can be directed to disruption of several functions. The conservation of FLPs genes among nematodes and its probable role in locomotion and reproduction has attracted attention for exploitation of these neuromodulator genes as possible targets for nematode management which is environmentally friendly and target specific (Piggott et al, 2011;Peymen et al, 2014;Morris et al, 2017). Quite a few neuropeptides have been identified in PPNs, and FMRFamide-like immune reactivity has also been recorded in the nervous systems of Heterodera glycines, Globodera Performance of transgenic plants was assessed in terms of number of galls, total endoparasites, egg masses, eggs per egg mass, and multiplication factor (MF) in different transgenic lines (#1-25-6, #2-27-4, #3-28-9, #4-36-12, #5-38-5, and #6-47-2) and WT plants at 35 DPI in soil.…”