Regulatory Evolution Offers Clues to Horn Diversification in Beetles

A comparative study of two closely related horned beetle species found that developing horn tissue has a dynamic cis-regulatory landscape, with regulatory features that vary between species and change according to sex and nutritional condition. The findings link this regulatory variation with the diversification of horns, while functional experiments provide evidence that two proteins in the bone morphogenetic protein signaling pathway contribute to horn development.

The researchers focused on the beetle genus Onthophagus, which includes species with sex- and nutrition-responsive horns used as secondary sexual weapons in reproductive competition. By comparing the gene-regulatory properties of horns in two closely related species with highly specialized, condition-biased phenotypes, the study examined how regulatory DNA may evolve alongside traits that respond to sex and nutrition.

The analysis identified mutational accumulation across species, condition-specific changes in chromatin accessibility within species, and the acquisition of lineage-specific regulatory elements. Many of the putative regulatory regions contained binding-site motifs associated with members of the bone morphogenetic protein signaling pathway, including developmental regulators. The authors also reported functional evidence that two proteins in this pathway had been co-opted for horn development and that their activity influenced horn shape and size across species, sexes and nutritional states.

Together, the results support a model in which evolutionarily labile cis-regulatory interactions modify the activity of conserved developmental pathways over short evolutionary timescales. The study is limited to the regulatory and functional analysis of horns in two beetle species, so it does not establish the same mechanism for horn diversification across the wider genus or for other condition-responsive traits. Its central finding is an association between regulatory evolution and trait diversification, supported by functional evidence for two bone morphogenetic protein pathway proteins.

Subject of Research: Comparative analysis of regulatory evolution and BMP signaling in horn diversification in Onthophagus beetles.

Article Title: The role of gene regulatory evolution in weapon diversification: Insights from comparative genomics, chromatin profiling, and functional analyses of BMP signaling in horned beetles

Article References: Davidson, P. L., Manley, I. G., & Moczek, A. P. (2026). The role of gene regulatory evolution in weapon diversification: Insights from comparative genomics, chromatin profiling, and functional analyses of BMP signaling in horned beetles. PLOS Genetics, 22(10), e1012338. https://doi.org/10.1371/journal.pgen.1012338

Image Credits: AI Generated

DOI: 10.1371/journal.pgen.1012338

Keywords: Onthophagus beetles, horn diversification, cis-regulatory evolution, chromatin accessibility, BMP signaling, comparative genomics, developmental pathways, sexual selection, role, gene, regulatory, evolution