Small peptide–mediated self-recognition prevents cannibalism in predatory nematodes

Abstract

Self-recognition is observed abundantly throughout the natural world, regulating diverse biological processes. Although ubiquitous, often little is known of the associated molecular machinery, and so far, organismal self-recognition has never been described in nematodes. We investigated the predatory nematode Pristionchus pacificus and, through interactions with its prey, revealed a self-recognition mechanism acting on the nematode surface, capable of distinguishing self-progeny from closely related strains. We identified the small peptide SELF-1, which is composed of an invariant domain and a hypervariable C terminus, as a key component of self-recognition. Modifications to the hypervariable region, including single–amino acid substitutions, are sufficient to eliminate self-recognition. Thus, the P. pacificus self-recognition system enables this nematode to avoid cannibalism while promoting the killing of competing nematodes.

Bacterial vitamin B12 production enhances nematode predatory behavior

“…Bite assays provide a more detailed and thorough analysis of the specific interactions associated with predatory behaviors. Bite assays were conducted as previously described [12,13,17]. Briefly, substantial C. elegans prey was generated by maintaining C. elegans cultures on E. coli OP50 bacteria until freshly starved resulting in an abundance of young larvae.…”

“…In addition, P. pacificus is an omnivorous nematode capable of feeding on bacteria, fungi, and also predating on other nematodes [11][12][13]. Predation is dependent on morphological and behavioral novelties, involving the formation of teeth-like denticles and a self-recognition mechanism [14][15][16][17]. The ability to form teeth-like denticles is an example of developmental plasticity with two discrete mouth forms [18].…”

Bacterial derived vitamin B12 enhances predatory behaviors in nematodes

“…We used two types of predation assays as described below. Corpse assays facilitated rapid quantification of predatory behavior and were conducted as previously described 6,10,33 . Briefly, in order to generate substantial C. elegans larvae for use as prey, cultures were maintained on E. coli OP50 bacteria until freshly starved resulting in an abundance of young larvae.…”

“…When post-feeding size measurement was required, predatory animals were picked to NGM plates containing no bacteria and measurements were taken using the Wormsizer plug in for Image J/Fiji 36 Bite assays provide a more detailed and thorough analysis of the specific interactions associated with predatory behaviors. Bite assays were conducted as previously described 6,10 . Briefly, substantial C. elegans prey was generated by maintaining C. elegans cultures on E. coli OP50 bacteria until freshly starved resulting in an abundance of young larvae.…”

“…In general, P. pacificus is an omnivorous nematode that can grow on bacteria, fungi and it can predate on other nematodes [4][5][6] . Predation is dependent on morphological and behavioral novelties, involving the formation of teeth-like denticles and a self-recognition mechanism [7][8][9][10] . The ability to form teeth-like denticles is an example of developmental plasticity with two discrete mouth-forms 11 .…”