Genetic and molecular determinants of nematode kin-recognition

• Applicant: James Lightfoot, Ph.D.
• Subject Area: Animal Physiology and Biochemistry ; Sensory and Behavioural Biology ; Cognitive, Systems and Behavioural Neurobiology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 495445600

The ability to distinguish self and kin from foreign entities has been observed across the natural world and is associated with a diverse spectrum of biological processes, including both cooperative and competitive behaviours. While behaviours associated with the identification of self and kin are commonplace, understanding the proximate mechanisms are challenging due to a lack of genetic, molecular and neurobiological techniques available in many of these organisms. Nematodes are a group of organisms without such limitations and have been used as a mainstay of organismal behavioural research. Further, the recently discovered self-recognition behaviours in the free-living nematode Pristionchus pacificus provides an ideal system to uncover the mechanism involved in unprecedented detail. P. pacificus are omnivorous nematodes capable of supplementing their bacterial diet by predating on the larvae of other nematodes. They also display cannibalistic behaviours towards conspecifics but do not cannibalise their kin. This kin-recognition system is dependent on the small peptide SELF-1, which contains a hypervariable region. However, while self-1 is undoubtably an important component in the self-signal, recent experiments exploring ecologically relevant con-specific interactions have demonstrated it is not the only factor involved. Here we propose to identify other signalling components and begin to understand the mechanism of kin-recognition in nematodes. As such, we have now identified an additional signalling component which is the adjacent gene to self-1 and has been named self-2. self-2 encodes a more substantial protein structure consisting of 249 amino acids including a transmembrane domain and is part of a two gene operon. Therefore, we will investigate this additional signalling factor by using CRISPR/Cas9 to generate new mutations in specific domains to assess its function and transgenes to investigate its expression. Additionally, we will use similar methods to explore the other operonic gene to identify if it is also involved in nematode kin-recognition. We will also use previously generated RNA-seq data sets to identify any regions of variability in these proteins. Furthermore, with direct contact of prey required for kin-recognition and the killing decision, the nematode surface coat of the cuticle is a prime candidate for the location of the kin-recognition signal. However, as nematodes go through several moults during development, this surface coat must be repeatedly replaced. As such, we will utilise state of the art mass spectrometry methods to determine the cuticle surface coat composition, any influence the self mutants may have on this, and how they may be replenished on the surface coat by using forward genetic screens to isolate mutants with defective self-1 expression. Thus, with this multifaceted approach we aim to elucidate fundamental aspects behind these kin-recognition signals.

• DFG Programme: Research Grants