title: Gain and Loss of Floral Scent Production through Changes in Structural Genes during Pollinator-Mediated Speciation.
abstract: The interactions of plants with their pollinators are thought to be a driving force in the evolution of angiosperms. Adaptation to a new pollinator involves coordinated changes in multiple floral traits controlled by multiple genes. Surprisingly, such complex genetic shifts have happened numerous times during evolution. Here we report on the genetic basis of the changes in one such trait, floral scent emission, in the genus Petunia (Solanaceae). The increase in the quantity and complexity of the volatiles during the shift from bee to hawkmoth pollination was due to de novo expression of the genes encoding benzoic acid/salicylic acid carboxyl methyltransferase (BSMT) and benzoyl-CoA:benzylalcohol/2-phenylethanol benzoyltransferase (BPBT) together with moderately increased transcript levels for most enzymes of the phenylpropanoid/benzenoid pathway. Loss of cinnamate-CoA ligase (CNL) function as well as a reduction in the expression of the MYB transcription factor ODO1 explain the loss of scent during the transition from moth to hummingbird pollination. The CNL gene in the hummingbird-adapted species is inactive due to a stop codon, but also appears to have undergone further degradation over time. Therefore, we propose that loss of scent happened relatively early in the transition toward hummingbird pollination, and probably preceded the loss of UV-absorbing flavonols. The discovery that CNL is also involved in the loss of scent during the transition from outcrossing to selfing in Capsella (Brassicaceae) (see the accompanying paper) raises interesting questions about the possible causes of deep evolutionary conservation of the targets of evolutionary change.
authors.affiliation: Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland.
authors.forename: Avichai
authors.initials: A
authors.lastname: Amrad
authors.affiliation: Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland.
authors.forename: Michel
authors.initials: M
authors.lastname: Moser
authors.affiliation: Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland.
authors.forename: Therese
authors.initials: T
authors.lastname: Mandel
authors.affiliation: Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, the Netherlands.
authors.forename: Michel
authors.initials: M
authors.lastname: de Vries
authors.affiliation: Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, the Netherlands.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Schuurink
authors.affiliation: Laboratory of Molecular Evolution, Department of Genetics, Universidade Federal do Rio Grande do Sul, P.O. Box 15053, Avenida Bento Goncalves, 9500 Porto Alegre, Brazil.
authors.forename: Loreta
authors.initials: L
authors.lastname: Freitas
authors.affiliation: Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland. Electronic address: cris.kuhlemeier@ips.unibe.ch.
authors.forename: Cris
authors.initials: C
authors.lastname: Kuhlemeier
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics; D035264:Flowers / Q000235:genetics* / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D049810:Genetic Speciation; D005838:Genotype; D009036:Moths / Q000502:physiology; D009812:Odorants; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D054817:Pollination / Q000502:physiology*; D020641:Polymorphism, Single Nucleotide; D040641:Quantitative Trait Loci
chemical_list: D010940:Plant Proteins
keywords: Petunia; benzenoids; floral volatile; pollination syndrome; speciation; speciation genes