Natural allelic variations of xenobiotic-metabolizing enzymes affect sexual dimorphism in Oryzias latipes.
Sexual dimorphisms, which are phenotypic differences between males and females, are driven by sexual selection. Interestingly, sexually selected traits show geographical variations within species despite strong directional selective pressures. This paradox has eluded many evolutionary biologists for some time, and several models have been proposed (e.g. 'indicator model' and 'trade-off model'). However, disentangling which of these theories explains empirical patterns remains difficult, because genetic polymorphisms that cause variation in sexual differences are still unknown. In this study, we show that polymorphisms in cytochrome P450 (CYP) 1B1, which encodes a xenobiotic-metabolizing enzyme, are associated with geographical differences in sexual dimorphism in the anal fin morphology of medaka fish (Oryzias latipes). Biochemical assays and genetic cross experiments show that high- and low-activity CYP1B1 alleles enhanced and declined sex differences in anal fin shapes, respectively. Behavioural and phylogenetic analyses suggest maintenance of the high-activity allele by sexual selection, whereas the low-activity allele possibly has experienced positive selection due to by-product effects of CYP1B1 in inferred ancestral populations. The present data can elucidate evolutionary mechanisms behind genetic variations in sexual dimorphism and indicate trade-off interactions between two distinct mechanisms acting on the two alleles with pleiotropic effects of xenobiotic-metabolizing enzymes.
Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan.
Takafumi
T
Katsumura
Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan.
Shoji
S
Oda
Risk Analysis Research Center, The Institute of Statistical Mathematics, Tachikawa, Tokyo, Japan.
Shigeki
S
Nakagome
Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan.
Tsunehiko
T
Hanihara
Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan.
Hiroshi
H
Kataoka
Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan.
Hiroshi
H
Mitani
Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan.
Shoji
S
Kawamura
Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan hiroki_oota@med.kitasato-u.ac.jp.
Hiroki
H
Oota
D000483:Alleles; D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D005260:Female; D029941:Fish Proteins / Q000235:genetics*; D005843:Geography; D008297:Male; D008969:Molecular Sequence Data; D009990:Oryzias / Q000033:anatomy & histology / Q000235:genetics* / Q000378:metabolism; D011110:Polymorphism, Genetic; D012727:Sex Characteristics; D012726:Sexual Behavior, Animal
D029941:Fish Proteins; D003577:Cytochrome P-450 Enzyme System
cytochrome P450; genetic polymorphisms; sexual dimorphism; sexual selection