title: Diversifying selection of the anthocyanin biosynthetic downstream gene UFGT accelerates floral diversity of island Scutellaria species.
abstract: Adaptive divergence, which usually explains rapid diversification within island species, might involve the positive selection of genes. Anthocyanin biosynthetic pathway (ABP) genes are important for floral diversity, and are related to stress resistance and pollination, which could be responsible for species diversification. Previous studies have shown that upstream genes of ABP are subject to selective constraints and have a slow evolutionary rate, while the constraints on downstream genes are lower.
  
  
  
  In this study, we confirmed these earlier observations of heterogeneous evolutionary rate in upstream gene CHS and the downstream gene UFGT, both of which were expressed in Scutellaria sp. inflorescence buds. We found a higher evolutionary rate and positive selection for UFGT. The codons under positive selection corresponded to the diversified regions, and the presence or absence of an α-helix might produce conformation changes in the Rossmann-like fold structure. The significantly high evolutionary rates for UFGT genes in Taiwanese lineages suggested rapid accumulation of amino acid mutations in island species. The results showed positive selection in closely related species and explained the high diversification of floral patterns in these recently diverged species. In contrast, non-synonymous mutation rate decreases in long-term divergent species could reduce mutational load and prevent the accumulation of deleterious mutations.
  
  
  
  Together with the positive selection of transcription factors for ABP genes described in a previous study, these results confirmed that positive selection takes place at a translational level and suggested that the high divergence of ABP genes is related to the floral diversity in island Scutellaria species.
authors.affiliation: Department of Life Science, National Taiwan Normal University, No. 88, Ting-Chow Rd, Sec 4, Taipei, Taiwan, 11677, Republic of China.
authors.forename: Bing-Hong
authors.initials: BH
authors.lastname: Huang
authors.affiliation: Department of Biological Science and Technology, National Pingtung University of Science and Technology, No. 1, Shuefu Road, Pingtung, Taiwan, 91201, Republic of China.
authors.forename: Yi-Wen
authors.initials: YW
authors.lastname: Chen
authors.affiliation: Department of Life Science, National Taiwan Normal University, No. 88, Ting-Chow Rd, Sec 4, Taipei, Taiwan, 11677, Republic of China.
authors.forename: Chia-Lung
authors.initials: CL
authors.lastname: Huang
authors.affiliation: The Key Laboratory for Silviculture and Conservation of Ministry of Education, College of Forestry, Beijing Forestry University, No.35, Tsinghua East Road, Beijing, 100083, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Gao
authors.affiliation: Department of Life Science, National Taiwan Normal University, No. 88, Ting-Chow Rd, Sec 4, Taipei, Taiwan, 11677, Republic of China. pcliao@ntnu.edu.tw.
authors.forename: Pei-Chun
authors.identifier: 0000-0003-1733-5504
authors.initials: PC
authors.lastname: Liao
mesh_terms: D000872:Anthocyanins / Q000096:biosynthesis*; D053898:Biosynthetic Pathways; D019143:Evolution, Molecular; D035264:Flowers / Q000378:metabolism; D017343:Genes, Plant; D010802:Phylogeny; D031363:Scutellaria / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D013624:Taiwan; D014157:Transcription Factors / Q000235:genetics
chemical_list: D000872:Anthocyanins; D014157:Transcription Factors
keywords: Anthocyanin biosynthetic pathway; CHS; Floral diversity; Island species; Positive selection; UFGT