Genetic mechanisms underlying parallel loss of photoperiodism and diversity of seasonal reproduction in sticklebacks

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K07469
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Evolutionary biology
• Research Institution: National Institute of Genetics
• Principal Investigator: Ishikawa Asano 国立遺伝学研究所, ゲノム・進化研究系, 助教 (20722101)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 季節性繁殖 / 日長応答性 / 甲状腺刺激ホルモン

Outline of Final Research Achievements

The timing of reproduction is one of the important life history traits that influence fitness. Some organisms use photoperiods to reproduce during favorable seasons, but others lose such photoperiodism. Compared to the theoretical studies, we know little about the molecular genetic mechanisms underlying variations in the timing of reproduction. To answer these questions, we use the threespine stickleback fish as a model. Ancestral marine ecotypes generally show seasonal reproduction, whereas derived freshwater ecotypes exhibit great diversity in both the timing and duration of reproduction. Transcriptome analysis showed that TSHb2 exhibits photoperiodic change in marine ecotypes, but not in multiple freshwater populations. TALEN-induced knockdown experiments demonstrated that TSHb2 has a pleiotropic role in suppressing gonadotropic hormone expression, sex steroid hormone secretion, gonad development and body growth under short days, which may underlie their long and early reproduction.

Free Research Field

進化生物学

Academic Significance and Societal Importance of the Research Achievements

甲状腺刺激ホルモンは、イトヨ以外の魚や鳥、哺乳類でも季節性繁殖の制御をおこなっていることが知られてきています。このため、イトヨ以外の他の生物でも、季節性繁殖の進化の鍵を担っていることが考えられます。この遺伝子を制御することにより、より長い期間繁殖する家畜種や養殖種の作成なども可能かもしれません。