| Title: | Structure-Activity Studies of Semiochemicals from the Spider Orchid Caladenia plicata for Sexual Deception |
| Author(s): | Bohman B; Karton A; Flematti GR; Scaffidi A; Peakall R; |
| Address: | "School of Molecular Sciences, The University of Western Australia, Crawley, WA, 6009, Australia. bjorn.bohman@uwa.edu.au. Research School of Biology, The Australian National University, Acton, ACT 2601, Australia. bjorn.bohman@uwa.edu.au. Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia. bjorn.bohman@uwa.edu.au. School of Molecular Sciences, The University of Western Australia, Crawley, WA, 6009, Australia. Research School of Biology, The Australian National University, Acton, ACT 2601, Australia" |
| DOI: | 10.1007/s10886-018-0946-0 |
| ISSN/ISBN: | 1573-1561 (Electronic) 0098-0331 (Linking) |
| Abstract: | "Sexually deceptive orchids attract specific pollinators by mimicking insect sex pheromones. Normally this mimicry is very specific and identical compounds have been identified from orchids and matching females of the pollinators. In this study, we conduct a detailed structure-activity investigation on isomers of the semiochemicals involved in the sexual attraction of the male pollinator of the spider orchid Caladenia plicata. This orchid employs an unusual blend of two biosynthetically unrelated compounds, (S)-beta-citronellol and 2-hydroxy-6-methylacetophenone, to lure its Zeleboria sp. thynnine wasp pollinator. We show that the blend is barely attractive when (S)-beta-citronellol is substituted with its enantiomer, (R)-beta-citronellol. Furthermore, none of the nine-possible alternative hydroxy-methylacetophenone regioisomers of the natural semiochemical are active when substituted for the natural 2-hydroxy-6-methylacetophenone. Our results were surprising given the structural similarity between the active compound and some of the analogues tested, and results from previous studies in other sexually deceptive orchid/wasp systems where substitution with analogues was possible. Interestingly, high-level ab initio and density functional theory calculations of the hydroxy-methylacetophenones revealed that the active natural isomer, 2-hydroxy-6-methylacetophenone, has the strongest intramolecular hydrogen bond of all regioisomers, which at least in part may explain the specific activity" |
| Keywords: | "Acetophenones/chemistry/metabolism Acyclic Monoterpenes Animals Biological Mimicry Female Isomerism Male Monoterpenes/chemistry/metabolism Orchidaceae/chemistry/*physiology Pheromones/chemistry/*metabolism *Pollination Sexual Behavior, Animal Spiders/*phy;" |
| Notes: | "MedlineBohman, Bjorn Karton, Amir Flematti, Gavin R Scaffidi, Adrian Peakall, Rod eng DE160101313/the Australian Research Council/ FT110100304/the Australian Research Council/ LP130100162/the Australian Research Council/ DP150102762/the Australian Research Council/ 2018/03/20 J Chem Ecol. 2018 May; 44(5):436-443. doi: 10.1007/s10886-018-0946-0. Epub 2018 Mar 17" |
