Biosynthesis of pollinator-attractive hydrocarbons by deceptive orchids

• Applicant: Professor Dr. Philipp Schlüter
• Subject Area: Plant Biochemistry and Biophysics ; Evolution and Systematics of Plants and Fungi ; Ecology and Biodiversity of Plants and Ecosystems ; Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 491673799

Alkene biosynthesis is an evolutionary novelty that underlies the highly specific pollinator attraction in sexually deceptive Ophrys orchids and thereby facilitates their rapid speciation. Here, alkenes of different chain-lengths and double-bond positions provide the species-specific signals controlling pollinator interaction. This provides a powerful example illustrating how the interplay between ecology, biochemistry and genetics can drive angiosperm species diversification, a pivotal process shaping the face of our planet. Unlike saturated alkanes, unsaturated alkenes are hydrocarbons rarely found in plant cuticles and their synthesis derives from an evolutionarily ancient pathway that underwent evolutionary change to enable production of unsaturated compounds. Alkene biosynthesis involves desaturation, elongation and decarbonylation of very-long-chain fatty acid precursors. Whilst genetic changes affecting desaturation, and hence alkene double-bonds, are reasonably well understood, we lack a detailed understanding of how changes at the elongation step, whether regulatory or enzymatic, affect alkene chain-length. Neither do we have an understanding of which evolutionary changes first enabled the synthesis of unsaturated in addition to saturated hydrocarbons in this plant group, although we may speculate that gene duplication and enzyme evolution of an aldehyde decarbonylase may have played a role. With this project, we intend to fill some pertinent gaps in our understanding by► (i) systematically evaluating fatty acid substrate specificity and catalytic potential of Ophrys ketoacyl-CoA synthase (KCS) homologues acting in elongation,► (ii) characterising the differences in substrate specificity among recently duplicated aldehyde decarbonylase (AD) enzymes,► (iii) identifying candidate regulators for gene expression of alkene biosynthetic enzymes, particularly KCS and AD genes.Addressing these questions at a biochemical level is necessary to understand both how metabolic pathways evolve and how the environment can exert selection upon biosynthetic processes and thereby lead to the generation of plant biodiversity.

• DFG Programme: Research Grants