Ancient origin and conserved gene function in terpene pheromone evolution of stink bugs and hemipteran insects

Authors: REBHOLZ, ZARLEY - Virginia Tech; LANCASTER, JASON - Virginia Tech; LAROSE, HAILEY - Virginia Tech; Khrimian, Ashot; LUCK, KATRIN - Max Planck Institute Of Chemical Ecology; Sparks, Michael; GENDREAU, KERRY - Virginia Tech; SHEWADE, LEENA - Sri International; KÖLLNER, TOBIAS - Max Planck Institute Of Chemical Ecology; Weber, Donald; Gundersen-Rindal, Dawn; O'MAILLE, PAUL - Sri International; MOROZOV, ALEXANDRE - Rutgers University; THOLL, DOROTHEA - Virginia Tech

Submitted to: Insect Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2022
Publication Date: 12/14/2022
Citation: Rebholz, Z., Lancaster, J., Larose, H., Khrimian, A., Luck, K., Sparks, M., Gendreau, K., Shewade, L., Köllner, T., Weber, D.C., Gundersen, D.E., O'Maille, P., Morozov, A., Tholl, D. 2022. Ancient origin and conserved gene function in terpene pheromone evolution of stink bugs and hemipteran insects. Insect Biochemistry and Molecular Biology. https://doi.org/10.1016/j.ibmb.2022.103879.
DOI: https://doi.org/10.1016/j.ibmb.2022.103879

Interpretive Summary: Small molecules synthesized by specialized metabolic pathways are used by insects for communication and defense. The origin of molecules involved in these pathways is poorly understood. Insects use specialized metabolites of molecules called terpenes as pheromones and defense compounds. It is becoming apparent that insects can synthesize these metabolites using enzymes with terpene synthase (TPS) activity, which are derived from other enzymes of the core terpene metabolic pathway. Microbes and plants maintain large families of well-characterized TPS genes, but in insects these appear to be smaller and are much less well understood. We show that the brown marmorated stink bug (Halyomorpha halys) and harlequin bug (Murgantia histrionica) maintain certain gene families with genes of conserved sequence and TPS function to make identical molecules as pheromone precursors. The same gene function is conserved in the southern green stink bug (Nezara viridula). Stink bug TPS enzymes are ancient and evolved over 100 million years ago and diverged in hemipteran TPS genes by ancient gene duplication and this event occurred independently from a similar evolution of TPS genes in beetles. Our study provides evidence for an ancient emergence of TPS genes in stink bugs and other hemipteran insects. Stink bugs rely on small gene families and conserved TPS gene function for terpene pheromone biosynthesis. This information will be used by scientists and those interested in pheromones of stink bugs for monitoring or biocontrol.

Technical Abstract: Background: Animals use diverse arrays of small molecules for communication and defense. These molecules are synthesized by specialized metabolic pathways; however, the origin of enzymes involved in these pathways is often poorly understood. Many insects release specialized metabolites of the large class of terpenes as pheromones and defense compounds in intra- and interspecific interactions. For instance, stink bugs (Pentatomidae) in the insect order Hemiptera emit structurally related sesquiterpenes as sex or aggregation pheromones. There is growing evidence that insects including stink bugs can make terpene specialized metabolites de novo by enzymes with terpene synthase (TPS) activity, which are evolutionary derived from isoprenyl diphosphate synthase (IDS) enzymes such as farnesyl diphosphate synthase (FPPS) of the core terpene metabolic pathway. In contrast to microbes and plants, which maintain large families of well-characterized TPS genes, the degree of diversification and the evolutionary trajectory of TPS genes in insects is largely unknown. Results: Here we show that stink bugs of different geographical origin and tribes, the brown marmorated stink bug (Halyomorpha halys) and the harlequin bug (Murgantia histrionica) maintain small FPPS-derived gene families with genes of conserved sequence and TPS function to make identical sesquiterpenes (sesquipiperitol) as precursors of their bisabolane-type pheromones. The same gene function is conserved in the southern green stink bug (Nezara viridula) independent of its role in pheromone biosynthesis. Stink bug TPS enzymes emerged under positive selection in two paralogous clades prior to the onset of pentatomid evolution approximately more than 100 million years ago coinciding with the evolution of flowering plants. Structural changes of TPS proteins from canonical FPPS proteins include modifications of residues presumably required for prenyl diphosphate substrate binding. Gene mining and phylogenetic analysis provide evidence for the evolution of non-canonical IDS (FPPS)-derived genes in several other hemipteran lineages in correlation with the presence of terpene pheromones or defense compounds. Phylogenetic and gene structural comparisons show that these IDS-type genes diverged from canonical hemipteran FPPS genes by ancient gene duplication and this event occurred independently from a similar emergence of TPS genes in beetles (Coleoptera). Conclusion: Our study provides evidence for an ancient emergence of FPPS-derived genes in stink bugs and other hemipteran insects under presumed selection for terpene mediated chemical interactions. Stink bugs rely on small gene families and conserved TPS gene function in terpene pheromone biosynthesis. Our findings further suggest differences in TPS gene diversification in insects and plants in conjunction with different modes of gene functionalization in chemical interactions.