Adaptive evolution of multi-copy hatching enzyme genes in Oryzias

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K18593
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Evolutionary biology
• Research Institution: Sophia University
• Principal Investigator: Kawaguchi Mari 上智大学, 理工学部, 准教授 (00612095)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: hatching enzyme / egg envelope

Outline of Final Research Achievements

Embryos are surrounded by egg envelope to protect from physical stress, and then, secrete hatching enzymes HCE and LCE to dissolve the envelope at hatching. In medaka, two isoforms of HCE having high sequence similarity show different optimum salinities for egg envelope digestion. In this study, we tried to figure out the amino acid residues responsible for the different optimal salinity between the two isoforms. We constructed various kinds of mutant recombinant HCEs, and determined their optimal salinity. As the results, we found that the change of optimal salinity was caused by several amino acid residues. We further determined nucleotide sequence of the HCE cluster of 5 fishes from genus Oryzias. Then, the optimal salinity of HCE of each species was examined from their recombinant HCEs. Based on these data, three amino acid residues were suggested to be most important for different optimal salinity of HCE.

Free Research Field

進化生物学

Academic Significance and Societal Importance of the Research Achievements

本研究の特色は、第一に、タンパク質レベルの実験を通して適応進化を論じる点である。本研究は、多重コピー遺伝子の活性の多様性と適応進化との関係について考察するもので、これによって進化生物学の分野に重要な知見を提供できると確信する。第二に、DNAレベルとタンパク質レベルの実証可能な実験系を導入して、マクロな多様化のメカニズムの解明にアプローチしている点である。タンパク質の機能を実際に観察しながら、具体的にどの部位のどのアミノ酸変異が環境への適応や生物の多様化に関わっているのかを詳細に解析しようとする点も、本研究の重要な特色である。