A small peptide produced in the skin of predatory nematodes prevents them from cannibalizing their immediate family members, while they feed upon their close relatives, a new study finds. The ability to recognize self is an important trait and regulates many crucial biological processes. While it's observed in a wide variety of organisms, the molecular mechanisms that underlie self-recognition systems are not well understood. This is particularly true for nematodes - one of the most well-studied organisms on the planet - in which the ability to discriminate self from other organisms has not yet been described. Previous research has shown that the predatory Pristionchus nematodes will feed on the larvae of other species of nematodes; however, it is unknown if this cannibalistic nature is due to their ability to discriminate amongst their own kin versus other species. James Lightfoot and colleagues investigated the prey interactions between Pristionchus , their kin and other nematode species and revealed a self-recognition system that enables Pristionchus nematodes to recognize their offspring. Over a series of experiments, predatory Pristionchus nematodes were observed killing and eating the larvae of other species, including closely related Pristionchus pacificus strains. However, the authors found that in each case, the killing and eating of self-progeny was avoided (see video). By mapping and comparing the genomes of two P. pacificus strains including after amino acid manipulations done with CRISPR/Cas9 to explore specific molecular drivers of self-recognition, Lightfoot et al. identified a peptide responsible - hypervariable small peptide SELF-1. Alterations to the self-1 gene resulted in elimination of self-recognition and individuals who lost the related peptide were promptly cannibalized by their own strains. According to the authors, the results demonstrate a likely molecular system P. pacificus use to prevent cannibalism.
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Science