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Ann Bot

Title:		Duplication and selection in beta-ketoacyl-ACP synthase gene lineages in the sexually deceptive Chiloglottis (Orchidaceace)
Author(s):		Wong DCJ; Amarasinghe R; Falara V; Pichersky E; Peakall R;
Address:		"Ecology and Evolution, Research School of Biology, The Australian National University, Acton, Australia. Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA"
Journal Title:		Ann Bot
Year:		2019
Volume:		123
Issue:		6
Page Number:		1053 - 1066
DOI:		10.1093/aob/mcz013
ISSN/ISBN:		1095-8290 (Electronic) 0305-7364 (Print) 0305-7364 (Linking)
Abstract:		"BACKGROUND AND AIMS: The processes of gene duplication, followed by divergence and selection, probably underpin the evolution of floral volatiles crucial to plant-insect interactions. The Australian sexually deceptive Chiloglottis orchids use a class of 2,5-dialkylcyclohexan-1,3-dione volatiles or 'chiloglottones' to attract specific male wasp pollinators. Here, we explore the expression and evolution of fatty acid pathway genes implicated in chiloglottone biosynthesis. METHODS: Both Chiloglottis seminuda and C. trapeziformis produce chiloglottone 1, but only the phylogenetically distinct C. seminuda produces this volatile from both the labellum callus and glandular sepal tips. Transcriptome sequencing and tissue-specific contrasts of the active and non-active floral tissues was performed. The effects of the fatty acid synthase inhibitor cerulenin on chiloglottone production were tested. Patterns of selection and gene evolution were investigated for fatty acid pathway genes. KEY RESULTS: Tissue-specific differential expression of fatty acid pathway transcripts was evident between active and non-active floral tissues. Cerulenin significantly inhibits chiloglottone 1 production in the active tissues of C. seminuda. Phylogenetic analysis of plant beta-ketoacyl synthase I (KASI), a protein involved in fatty acid biosynthesis, revealed two distinct clades, one of which is unique to the Orchidaceae (KASI-2B). Selection analysis indicated a strong signal of positive selection at the split of KASI-2B followed by relaxed purifying selection in the Chiloglottis clade. CONCLUSIONS: By capitalizing on a phylogenetically distinct Chiloglottis from earlier studies, we show that the transcriptional and biochemical dynamics linked to chiloglottone biosynthesis in active tissues are conserved across Chiloglottis. A combination of tissue-specific expression and relaxed purifying selection operating at specific fatty acid pathway genes may hold the key to the evolution of chiloglottones"
Keywords:		*3-Oxoacyl-(Acyl-Carrier-Protein) Synthase Animals Australia Flowers Male *Orchidaceae Phylogeny Pollination Chiloglottis chiloglottone evolution fatty acid gene duplication selection sexual deception transcriptome;
Notes:		"MedlineWong, Darren C J Amarasinghe, Ranamalie Falara, Vasiliki Pichersky, Eran Peakall, Rod eng Research Support, Non-U.S. Gov't England 2019/02/23 Ann Bot. 2019 Jun 24; 123(6):1053-1066. doi: 10.1093/aob/mcz013"