# O-acyltransferase genes involved in the production of volatile sex pheromones in Caenorhabditis elegans

## TL;DR

Researchers identified four O-acyltransferase genes in C. elegans that are essential for producing volatile sex pheromones, which attract males.

## Contribution

The study reveals functional specialization among OAC gene paralogs in pheromone biosynthesis and signaling.

## Key findings

- Four OAC genes (oac-13, oac-16, oac-25, oac-28) are required for volatile sex pheromone production.
- OAC-13 and OAC-16 are necessary for both major pheromone components, while OAC-25 and OAC-28 regulate one component.
- OAC genes also modulate nonvolatile ascaroside pheromone synthesis and secretion.

## Abstract

As a step toward identification of the volatile sex pheromones (VSPs) that attract males as well as to understand where and under what conditions they are produced, we sought to identify genes necessary for VSP production. We generated loss-of-function mutants of 56 oac genes, finding that four are necessary for production of the (VSPs). VSPs are made up of at least two components, identified by their differential behavior in GC-MS. oac-13 and oac-16 are necessary for both major VSP components, while the tandem paralogs oac-25 and oac-28 are necessary for only one component. We found that oac-16, oac-25, and oac-28 have specific expression in the epidermal “seam” cells, implicating these lateral midline cells as the principal sites of VSP biosynthesis.

Gene family expansions are critical for functional diversification, yet the contributions of paralogs to metabolic pathways are often unclear. In Caenorhabditis, the expanded O-acyltransferase (OAC) family—enzymes that transfer acyl groups to hydroxylated substrates—remains poorly characterized despite having been implicated in lipid metabolism. Using CRISPR-Cas9 mutagenesis, behavioral assays, gas chromatographic-mass spectral (GC-MS) analyses, and metabolomics, we systematically analyzed 59 OAC-family protein-coding genes to define their roles in regulating signaling molecules. We found that four adjacent paralogs (oac-13, oac-16, oac-25, and oac-28) on chromosome I are required for synthesizing volatile sex pheromones—airborne signals critical for male mate-searching. Specifically, oac-13 and oac-16 are necessary for producing both major pheromone components, while the identical tandem paralogs oac-25 and oac-28 regulate the production of the later-eluting component in gas chromatography. Disruption of these genes reduced production of key pheromone components and impaired male attraction. Metabolomics revealed that oac-16 and other OACs also modulate the synthesis and secretion of nonvolatile ascaroside pheromones, indicating dual roles in chemical signaling. This work uncovers functional specialization within an expanded gene family, illustrating how redundancy and divergence enable adaptive evolution of communication systems.