Doyle A, Cowan M E, Migaud H, Wright P J, Davie A
Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, UK; Marine Scotland Science, 375 Victoria Road, Aberdeen AB11 9DB, UK.
Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, UK.
Comp Biochem Physiol A Mol Integr Physiol. 2021 Oct;260:111000. doi: 10.1016/j.cbpa.2021.111000. Epub 2021 Jun 2.
Evidence from mammals and aves alludes to a possibly conserved seasonal photoperiod induced neuroendocrine cascade which stimulates subsequent sexual maturation however our understanding of this mechanism in teleosts is lacking. Unlike all teleosts studied to date, the Atlantic cod (Gadus morhua) is a short day breeder with the reduction in day-length from the summer solstice stimulating gametogenesis. Cod specific orthologues of eya3, tshβ and dio2 were identified and their expression was monitored in the brain and pituitary of cod held under either stimulated or inhibited photoperiod conditions. While no differential expression was apparent in brain dio2 & tshβ and pituitary tshβ, there was significant temporal variation in expression of pituitary eya3 under the SNP treatment, with expression level elevating in association with active gametogenesis. Under the LL treatment, sexual maturation was inhibited and there was a corresponding suppression of eya3 expression. In a second study the impact of size/energetic status on the initiation of sexual maturation was investigated. In the feed restricted population maturation was significantly suppressed (5% sexually mature) compared to the ab libitum fed stock (95% sexually mature) with there being a concomitant significant suppression in pituitary eya3 expression. Overall, these results suggest that pituitary eya3 has the potential to act as an integrator of both environmental and energetic regulation of sexual maturation of cod. Being the first account of eya3 induction in a short day breeding teleost, the conserved association with stimulation of reproduction and not seasonal state indicates that the upstream drivers which initiate the pathway differ among vertebrates according to their breeding strategies, but the pathway itself and its role in the reproductive cascade appears to be conserved across the vertebrate clade.
来自哺乳动物和鸟类的证据表明，可能存在一种保守的季节性光周期诱导神经内分泌级联反应，该反应会刺激随后的性成熟，然而我们对硬骨鱼中这种机制的了解却很匮乏。与迄今为止研究的所有硬骨鱼不同，大西洋鳕鱼（Gadus morhua）是一种短日照繁殖鱼类，从夏至开始日长缩短会刺激配子发生。已鉴定出eya3、tshβ和dio2的鳕鱼特异性直系同源物，并在处于刺激或抑制光周期条件下的鳕鱼的脑和垂体中监测它们的表达。虽然脑dio2和tshβ以及垂体tshβ中没有明显的差异表达，但在SNP处理下垂体eya3的表达存在显著的时间变化，其表达水平随着活跃的配子发生而升高。在长日照处理下，性成熟受到抑制，eya3的表达也相应受到抑制。在第二项研究中，研究了大小/能量状态对性成熟起始的影响。与自由摄食的群体（95%性成熟）相比，限食群体的成熟受到显著抑制（5%性成熟），同时垂体eya3的表达也受到显著抑制。总体而言，这些结果表明垂体eya3有可能作为鳕鱼性成熟的环境和能量调节的整合因子。作为首次在短日照繁殖硬骨鱼中诱导eya3的报道，其与繁殖刺激而非季节性状态的保守关联表明，根据繁殖策略，启动该途径的上游驱动因素在脊椎动物中有所不同，但该途径本身及其在生殖级联反应中的作用似乎在整个脊椎动物类群中是保守的。
