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Curr Biol

Title:		An unusual tricosatriene is crucial for male fungus gnat attraction and exploitation by sexually deceptive Pterostylis orchids
Author(s):		Hayashi T; Bohman B; Scaffidi A; Peakall R; Flematti GR;
Address:		"Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, ACT 2600, Australia; School of Molecular Sciences, The University of Western Australia, Crawley, WA 6009, Australia. Electronic address: tobias.hayashi@anu.edu.au. Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, ACT 2600, Australia; School of Molecular Sciences, The University of Western Australia, Crawley, WA 6009, Australia; Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Lomma 23422, Sweden. School of Molecular Sciences, The University of Western Australia, Crawley, WA 6009, Australia. Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, ACT 2600, Australia; School of Molecular Sciences, The University of Western Australia, Crawley, WA 6009, Australia"
Journal Title:		Curr Biol
Year:		2021
Volume:		20210325
Issue:		9
Page Number:		1954 - 1961
DOI:		10.1016/j.cub.2021.01.095
ISSN/ISBN:		1879-0445 (Electronic) 0960-9822 (Linking)
Abstract:		"Cross-kingdom mimicry of female insect sex pheromones by sexually deceptive orchids has evolved multiple times.(1) Fungus gnats (Diptera) are predicted to be pollinators of hundreds of sexually deceptive orchids,(2-4) yet unlike orchids that sexually attract bees and wasps (Hymenoptera),(5-11) the chemistry of fungus gnat-pollinated orchids remains unknown. Furthermore, despite the importance of fungus gnats as pollinators, pests, and decomposers of organic material, and evidence for sex pheromones since 1971,(12-17) no structure of any fungus gnat sex pheromone has to date been confirmed. In this study, we found a mixture of five hydrocarbons shared between Pterostylis orbiculata orchids and female Mycomya sp. (Mycetophilidae) fungus gnats, which included three alkanes, a C(23) diene, and a C(23) triene. The triene was an undescribed natural product, which we synthesized and confirmed to be (6Z,9Z)-1,6,9-tricosatriene. Field bioassays with a synthetic blend of the five hydrocarbons elicited attraction and sexual behavior from male gnats. The triene alone elicited attraction and low levels of sexual behavior, but the blend without it was unattractive, suggesting that this compound is a key component of orchid pollinator attraction and the female fungus gnat sex pheromone. In two closely related Pterostylis species, we found related C(23) trienes, but not (6Z,9Z)-1,6,9-tricosatriene. These results suggest that unusual long-chain unsaturated hydrocarbons hold the key to sexual deception in Pterostylis orchids, and are an important step toward deciphering female fungus gnat sex pheromones"
Keywords:		"Animals Bees Flowers Fungi *Orchidaceae Pheromones Pollination *Sex Attractants (6Z, 9Z)-1, 6, 9-tricosatriene Mycetophilidae Orchidaceae Pterostylis chemical mimicry floral volatile fungus gnat semiochemical sex pheromone sexual deception;"
Notes:		"MedlineHayashi, Tobias Bohman, Bjorn Scaffidi, Adrian Peakall, Rod Flematti, Gavin R eng Research Support, Non-U.S. Gov't England 2021/03/27 Curr Biol. 2021 May 10; 31(9):1954-1961.e7. doi: 10.1016/j.cub.2021.01.095. Epub 2021 Mar 25"