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PLoS Genet

Title:		The genetic basis of pollinator adaptation in a sexually deceptive orchid
Author(s):		Xu S; Schluter PM; Grossniklaus U; Schiestl FP;
Address:		"Institute of Systematic Botany and Zurich-Basel Plant Science Center, University of Zurich, Zurich, Switzerland. sxu@ice.mpg.de"
Journal Title:		PLoS Genet
Year:		2012
Volume:		20120816
Issue:		8
Page Number:		e1002889 -
DOI:		10.1371/journal.pgen.1002889
ISSN/ISBN:		1553-7404 (Electronic) 1553-7390 (Print) 1553-7390 (Linking)
Abstract:		"In plants, pollinator adaptation is considered to be a major driving force for floral diversification and speciation. However, the genetic basis of pollinator adaptation is poorly understood. The orchid genus Ophrys mimics its pollinators' mating signals and is pollinated by male insects during mating attempts. In many species of this genus, chemical mimicry of the pollinators' pheromones, especially of alkenes with different double-bond positions, plays a key role for specific pollinator attraction. Thus, different alkenes produced in different species are probably a consequence of pollinator adaptation. In this study, we identify genes that are likely involved in alkene biosynthesis, encoding stearoyl-acyl carrier protein (ACP) desaturases (SAD), in three closely related Ophrys species, O. garganica, O. sphegodes, and O. exaltata. Combining floral odor and gene expression analyses, two SAD homologs (SAD1/2) showed significant association with the production of (Z)-9- and (Z)-12-alkenes that were abundant in O. garganica and O. sphegodes, supporting previous biochemical data. In contrast, two other newly identified homologs (SAD5/6) were significantly associated with (Z)-7-alkenes that were highly abundant only in O. exaltata. Both molecular evolutionary analyses and pollinator preference tests suggest that the alkenes associated with SAD1/2 and SAD5/6 are under pollinator-mediated divergent selection among species. The expression patterns of these genes in F(1) hybrids indicate that species-specific expression differences in SAD1/2 are likely due to cis-regulation, while changes in SAD5/6 are likely due to trans-regulation. Taken together, we report a genetic mechanism for pollinator-mediated divergent selection that drives adaptive changes in floral alkene biosynthesis involved in reproductive isolation among Ophrys species"
Keywords:		"*Adaptation, Physiological Alkenes/isolation & purification Animals Biological Evolution Flowers/classification/*physiology Gene Expression Hybridization, Genetic Insecta/physiology Isoenzymes/genetics/metabolism Male Mixed Function Oxygenases/*genetics/m;"
Notes:		"MedlineXu, Shuqing Schluter, Philipp M Grossniklaus, Ueli Schiestl, Florian P eng Research Support, Non-U.S. Gov't 2012/08/24 PLoS Genet. 2012; 8(8):e1002889. doi: 10.1371/journal.pgen.1002889. Epub 2012 Aug 16"