Evolution of proteins involved in the final steps of juvenile hormone synthesis

Juvenile hormone (JH), a sesquiterpenoid produced by the insect corpus allatum gland (CA), is a key regulator of insect metamorphosis, reproduction, caste differentiation, and polyphenism. The first part of JH biosynthesis occurs via the universal eukaryotic mevalonate pathway. The final steps involve epoxidation and methylation. However, the sequence of these steps might not be conserved among all insects and Crustacea. Therefore, we used available genomic and transcriptomic data and identified JH acid methyltransferase (JHAMT), analyzed their genomic duplications in selected model organisms, and reconstructed their phylogeny. We have further reconstructed phylogeny of FAMeT proteins and show that evolution of this protein group is more complicated than originally appreciated. The analysis delineates important milestones in the evolution of several JH biosynthetic enzymes in arthropods, reviews major literature data on the last steps of JH synthesis, and defines questions and some hypotheses worth pursuing experimentally.