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Curr Biol

Title:		Complex Sexual Deception in an Orchid Is Achieved by Co-opting Two Independent Biosynthetic Pathways for Pollinator Attraction
Author(s):		Xu H; Bohman B; Wong DCJ; Rodriguez-Delgado C; Scaffidi A; Flematti GR; Phillips RD; Pichersky E; Peakall R;
Address:		"Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA. Research School of Biology, The Australian National University, Acton, ACT 2601, Australia; Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia; 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. 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; Kings Park and Botanic Garden, The Botanic Garden and Parks Authority, West Perth, WA 6005, Australia; School of Plant Biology, The University of Western Australia, Crawley, WA 6009, Australia. Research School of Biology, The Australian National University, Acton, ACT 2601, Australia; School of Molecular Sciences, The University of Western Australia, Crawley, WA 6009, Australia. Electronic address: rod.peakall@anu.edu.au"
Journal Title:		Curr Biol
Year:		2017
Volume:		20170615
Issue:		13
Page Number:		1867 - 1877
DOI:		10.1016/j.cub.2017.05.065
ISSN/ISBN:		1879-0445 (Electronic) 0960-9822 (Linking)
Abstract:		"Sexually deceptive orchids lure their specific male pollinators using volatile semiochemicals that mimic female sex pheromones. To date, the semiochemicals known to be involved consist of blends of chemically and biosynthetically related compounds. In contrast, we report that (S)-beta-citronellol and 2-hydroxy-6-methylacetophenone, two biosynthetically distinct compounds, are the active semiochemicals in Caladenia plicata, which is pollinated by male Zeleboria sp. thynnine wasps. They are also sex pheromone components of the female Zeleboria. A 1:4 blend elicits a high rate of attempted copulation ( approximately 70%) in bioassays, equivalent to rates observed at orchid flowers. Whereas beta-citronellol is well known, 2-hydroxy-6-methylacetophenone appears to be previously unknown as a floral volatile. Production of the two compounds is restricted to glandular sepal tips; thus, differential expression analysis of contrasting floral tissue transcriptomes was employed to illuminate the biosynthesis. As expected, production of (S)-beta-citronellol commences with the terpene synthase GES1 catalyzing the irreversible conversion of geranyl diphosphate (GPP) to geraniol. Contrary to prediction, biosynthesis subsequently proceeds in three steps, commencing with the oxidation of geraniol to geranial by alcohol dehydrogenase ADH3, followed by the enantioselective reduction of a double bond in geranial by geranial reductase GER1 to give (S)-beta-citronellal. Finally, ADH3-catalyzed reduction of (S)-beta-citronellal results in (S)-beta-citronellol. In line with previous work on insects showing that 2-hydroxy-6-methylacetophenone is derived from a polyketide pathway, we report a differentially expressed polyketide synthase (PKS) gene candidate. Thus, in this unique example of sexual deception, pollination is achieved by co-opting and regulating two independent biosynthetic pathways of floral volatile compounds. VIDEO ABSTRACT"
Keywords:		Animals Biosynthetic Pathways Orchidaceae/genetics/*physiology Pheromones/*metabolism Plant Proteins/*genetics/metabolism *Pollination Sex Attractants/analysis Volatile Organic Compounds/metabolism Wasps/physiology (S)-beta-citronellol 2-hydroxy-6-methyla;
Notes:		"MedlineXu, Haiyang Bohman, Bjorn Wong, Darren C J Rodriguez-Delgado, Claudia Scaffidi, Adrian Flematti, Gavin R Phillips, Ryan D Pichersky, Eran Peakall, Rod eng England 2017/06/20 Curr Biol. 2017 Jul 10; 27(13):1867-1877.e5. doi: 10.1016/j.cub.2017.05.065. Epub 2017 Jun 15"