title: Positive selection sites in tertiary structure of Leguminosae chalcone isomerase 1.
abstract: Isoflavonoids and the related synthesis enzyme, chalcone isomerase 1 (CHI1), are unique in the Leguminosae, with diverse biological functions. Among the Leguminosae, the soybean is an important oil, protein crop, and model plant. In this study, we aimed to detect the generation pattern of Leguminosae CHI1. Genome-wide sequence analysis of CHI in 3 Leguminosae and 3 other closely related model plants was performed; the expression levels of soybean chalcone isomerases were also analyzed. By comparing positively selected sites and their protein structures, we retrieved the evolution patterns for Leguminosae CHI1. A total of 28 CHI and 7 FAP3 (CHI4) genes were identified and separated into 4 clades: CHI1, CHI2, CHI3, and FAP3. Soybean genes belonging to the same chalcone isomerase subfamily had similar expression patterns. CHI1, the unique chalcone isomerase subfamily in Leguminosae, showed signs of significant positive selection as well as special expression characteristics, indicating an accelerated evolution throughout its divergence. Eight sites were identified as undergoing positive selection with high confidence. When mapped onto the tertiary structure of CHI1, these 8 sites were observed surrounding the enzyme substrate only; some of them connected to the catalytic core of CHI. Thus, we inferred that the generation of Leguminosae CHI1 is dependent on the positively selected amino acids surrounding its catalytic substrate. In other words, the evolution of CHI1 was driven by specific selection or processing conditions within the substrate.
authors: Jiujiang Laboratory for Seed Quality of Soybean National Center for Soybean Improvement, Research Center for Soybean, College of Life Science, Jiujiang University, Jiangxi Province, China.
authors: R K
authors: RK
authors: Wang
authors: Jiujiang Laboratory for Seed Quality of Soybean National Center for Soybean Improvement, Research Center for Soybean, College of Life Science, Jiujiang University, Jiangxi Province, China.
authors: S F
authors: SF
authors: Zhan
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Soybean Research Institute, National Center for Soybean Improvement, Nanjing Agricultural University, Jiangsu Province, China.
authors: T J
authors: TJ
authors: Zhao
authors: Jiujiang Laboratory for Seed Quality of Soybean National Center for Soybean Improvement, Research Center for Soybean, College of Life Science, Jiujiang University, Jiangxi Province, China.
authors: X L
authors: XL
authors: Zhou
authors: Jiujiang Laboratory for Seed Quality of Soybean National Center for Soybean Improvement, Research Center for Soybean, College of Life Science, Jiujiang University, Jiangxi Province, China soybeanw@163.com.
authors: C E
authors: CE
authors: Wang
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D019143:Evolution, Molecular; D018745:Genome, Plant; D019753:Intramolecular Lyases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012641:Selection, Genetic; D013025:Glycine max / Q000145:classification / Q000201:enzymology* / Q000235:genetics*
chemical_list: D010940:Plant Proteins; D019753:Intramolecular Lyases; C019865:chalcone isomerase