Bulk segregant analysis for the genetic mapping of low MMB chemotaxis C. elegans strains
Predator-prey interactions drive behavioral adaptation for survival. However, the underlying genetic basis remains unclear in most systems. Caenorhabditis elegans naturally encounters the predatory fungus Arthrobotrys oligospora, which is known to produce a highly attractive sex pheromone mimicry, methyl 3-methyl-2-butenoate (MMB) to lure C. elegans. We observed that attraction to the MMB is polymorphic across wild C. elegans isolates. Significantly, the Taiwanese strain TWN2542, isolated alongside A. oligospora, showed markedly reduced MMB attraction, hinting at an adaptive evolutionary response to this specific predatory threat. To uncover the genetic underpinnings of this behavioral shift, genetic mapping across 6 independent low-MMB-chemotaxis strains identified a shared quantitative trait locus on chromosome IV, which we subsequently narrowed down to a causal GPCR gene, str-268. Our research revealed that functional knockout of str-268 via CRISPR abolishes MMB chemotaxis in C. elegans. Moreover, disrupting its homolog in the distantly related male-female nematode C. afra not only eliminated MMB attraction but also disrupted mating behavior, highlighting the conserved role of this receptor and revealing the survival-reproduction conflict. These results underscore the complex interplay between survival and reproduction driven by predator-prey interactions, shed light on the evolutionary forces shaping behavioral adaptations across the tree of life.