title: Opsins have evolved under the permanent heterozygote model: insights from phylotranscriptomics of Odonata.
abstract: Gene duplication plays a central role in adaptation to novel environments by providing new genetic material for functional divergence and evolution of biological complexity. Several evolutionary models have been proposed for gene duplication to explain how new gene copies are preserved by natural selection, but these models have rarely been tested using empirical data. Opsin proteins, when combined with a chromophore, form a photopigment that is responsible for the absorption of light, the first step in the phototransduction cascade. Adaptive gene duplications have occurred many times within the animal opsins' gene family, leading to novel wavelength sensitivities. Consequently, opsins are an attractive choice for the study of gene duplication evolutionary models. Odonata (dragonflies and damselflies) have the largest opsin repertoire of any insect currently known. Additionally, there is tremendous variation in opsin copy number between species, particularly in the long-wavelength-sensitive (LWS) class. Using comprehensive phylotranscriptomic and statistical approaches, we tested various evolutionary models of gene duplication. Our results suggest that both the blue-sensitive (BS) and LWS opsin classes were subjected to strong positive selection that greatly weakens after multiple duplication events, a pattern that is consistent with the permanent heterozygote model. Due to the immense interspecific variation and duplicability potential of opsin genes among odonates, they represent a unique model system to test hypotheses regarding opsin gene duplication and diversification at the molecular level.
authors.affiliation: Department of Biology, Brigham Young University, Provo, UT, 84602, USA.
authors.forename: Anton
authors.initials: A
authors.lastname: Suvorov
authors.affiliation: Department of Biology, Brigham Young University, Provo, UT, 84602, USA.
authors.forename: Nicholas O
authors.initials: NO
authors.lastname: Jensen
authors.affiliation: Department of Biology, Brigham Young University, Provo, UT, 84602, USA.
authors.forename: Camilla R
authors.initials: CR
authors.lastname: Sharkey
authors.affiliation: Computer Science Department, Brigham Young University, Provo, UT, 84602, USA.
authors.forename: M Stanley
authors.initials: MS
authors.lastname: Fujimoto
authors.affiliation: Computer Science Department, Brigham Young University, Provo, UT, 84602, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Bodily
authors.affiliation: Department of Biology, Brigham Young University, Provo, UT, 84602, USA.
authors.forename: Haley M Cahill
authors.initials: HM
authors.lastname: Wightman
authors.affiliation: Department of Biology, Utah Valley University, Orem, UT, 84058, USA.
authors.forename: T Heath
authors.initials: TH
authors.lastname: Ogden
authors.affiliation: Computer Science Department, Brigham Young University, Provo, UT, 84602, USA.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Clement
authors.affiliation: Department of Biology, Brigham Young University, Provo, UT, 84602, USA.
authors.forename: Seth M
authors.initials: SM
authors.lastname: Bybee
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D020440:Gene Duplication; D017344:Genes, Insect; D006579:Heterozygote; D063191:Odonata / Q000235:genetics*; D055355:Opsins / Q000235:genetics*; D010802:Phylogeny
chemical_list: D055355:Opsins
keywords: Bayesian model; gene duplications; insect vision; positive selection