title: Repeated Inactivation of the First Committed Enzyme Underlies the Loss of Benzaldehyde Emission after the Selfing Transition in Capsella.
abstract: The enormous species richness of flowering plants is at least partly due to floral diversification driven by interactions between plants and their animal pollinators [1, 2]. Specific pollinator attraction relies on visual and olfactory floral cues [3-5]; floral scent can not only attract pollinators but also attract or repel herbivorous insects [6-8]. However, despite its central role for plant-animal interactions, the genetic control of floral scent production and its evolutionary modification remain incompletely understood [9-13]. Benzenoids are an important class of floral scent compounds that are generated from phenylalanine via several enzymatic pathways [14-17]. Here we address the genetic basis of the loss of floral scent associated with the transition from outbreeding to selfing in the genus Capsella. While the outbreeding C. grandiflora emits benzaldehyde as a major constituent of its floral scent, this has been lost in the selfing C. rubella. We identify the Capsella CNL1 gene encoding cinnamate:CoA ligase as responsible for this variation. Population genetic analysis indicates that CNL1 has been inactivated twice independently in C. rubella via different novel mutations to its coding sequence. Together with a recent study in Petunia [18], this identifies cinnamate:CoA ligase as an evolutionary hotspot for mutations causing the loss of benzenoid scent compounds in association with a shift in the reproductive strategy of Capsella from pollination by insects to self-fertilization.
authors.affiliation: Institute for Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Straße 24-25, 14476 Potsdam-Golm, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Sas
authors.affiliation: Institute of Biology, Dahlem Centre of Plant Sciences (DCPS), Freie Universität Berlin, Haderslebener Straße 9, 12163 Berlin, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Müller
authors.affiliation: Institute for Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Straße 24-25, 14476 Potsdam-Golm, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Kappel
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2, Canada.
authors.forename: Tyler V
authors.initials: TV
authors.lastname: Kent
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2, Canada.
authors.forename: Stephen I
authors.initials: SI
authors.lastname: Wright
authors.affiliation: Institute of Biology, Dahlem Centre of Plant Sciences (DCPS), Freie Universität Berlin, Haderslebener Straße 9, 12163 Berlin, Germany.
authors.forename: Monika
authors.initials: M
authors.lastname: Hilker
authors.affiliation: Institute for Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Straße 24-25, 14476 Potsdam-Golm, Germany. Electronic address: michael.lenhard@uni-potsdam.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Lenhard
mesh_terms: D000818:Animals; D001547:Benzaldehydes / Q000737:chemistry / Q000378:metabolism*; D005075:Biological Evolution; D029687:Capsella / Q000201:enzymology* / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D007178:Inbreeding; D007313:Insecta; D008025:Ligases / Q000235:genetics / Q000378:metabolism*; D009812:Odorants; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D054817:Pollination; D040641:Quantitative Trait Loci
chemical_list: D001547:Benzaldehydes; D010940:Plant Proteins; D008025:Ligases; C032175:benzaldehyde
keywords: Capsella; benzaldehyde; cinnamate:CoA ligase; floral scent; selfing syndrome; shepherd’s purse