Yatung Subu, Trivedi Amit Kumar
Department of Zoology, Mizoram University, Aizawl, India.
J Neuroendocrinol. 2025 Jun;37(6):e13478. doi: 10.1111/jne.13478. Epub 2024 Dec 11.
The population responds to environmental variability largely determined by the dynamic interactions between fitness components within- and among-individual variation in the expression of the environmentally sensitive phenotype. The study was conducted on daily and seasonal changes in the expression of steroidogenic gene markers and corresponding seasonal changes in the physiological characters in adult male tree sparrows. Two experiments were performed. In experiment one, birds (n = 5/time points) were sampled during the breeding season at 6-time points, i.e., ZT1, ZT5, ZT9, ZT13, ZT17, and ZT21 [Zeitgeber time (ZT) 0 = sun rise time at the respective time of the year], and daily variation in expression of steroidogenic markers was observed in hypothalamus and testes tissues. In experiment two, birds (n = 5/month) were sampled every month at mid-day for a year. Body mass, bill color, testes size, and molt in feathers were recorded. The hypothalamus and testes tissues were used for gene expression studies. Blood plasma cholesterol and testosterone levels were measured. Higher testicular volumes were recorded from March to May, whereas maximum molt was observed during the post-breeding phase. Plasma cholesterol levels were highest before the breeding phase. Higher testosterone levels corresponded with the breeding phase. Higher expressions of thyroid-stimulating hormone subunit beta (tshβ), type 2 deiodinase (dio2), and gonadotropin-releasing hormone (gnrh) during the breeding phase and higher expression of type 3 deiodinase (dio3) and gonadotropin-inhibitory hormone (gnih) were observed during the non-breeding phase. The steroidogenic transcripts showed seasonal changes in their expression in the hypothalamic and testicular tissue and were upregulated either during the pre-breeding or breeding phase. The study reveals that mRNA levels of steroidogenic enzymes exhibit daily rhythmicity both in the hypothalamus and testis tissues. Further, steroidogenic transcripts show seasonal variations that correspond to the annual reproductive cycle of the tree sparrow (Passer montanus).
种群对环境变化的响应很大程度上取决于环境敏感表型表达中个体内和个体间适应度成分之间的动态相互作用。该研究针对成年雄性树麻雀类固醇生成基因标记物表达的每日和季节性变化以及生理特征的相应季节性变化展开。进行了两项实验。在实验一中，在繁殖季节的6个时间点（即ZT1、ZT5、ZT9、ZT13、ZT17和ZT21 [授时时间（ZT）0 = 一年中相应时间的日出时间]）对鸟类（每个时间点n = 5只）进行采样，观察下丘脑和睾丸组织中类固醇生成标记物表达的每日变化。在实验二中，一年中每月中午对鸟类（每月n = 5只）进行采样。记录体重、喙的颜色、睾丸大小和羽毛换羽情况。下丘脑和睾丸组织用于基因表达研究。测量血浆胆固醇和睾酮水平。3月至5月记录到较高的睾丸体积，而在繁殖后期观察到最大换羽量。繁殖期前血浆胆固醇水平最高。较高的睾酮水平与繁殖期相对应。在繁殖期观察到促甲状腺激素β亚基（tshβ）、2型脱碘酶（dio2）和促性腺激素释放激素（gnrh）的较高表达，在非繁殖期观察到3型脱碘酶（dio3）和促性腺激素抑制激素（gnih）的较高表达。类固醇生成转录本在下丘脑和睾丸组织中的表达呈现季节性变化，并且在繁殖前期或繁殖期上调。该研究表明，类固醇生成酶的mRNA水平在下丘脑和睾丸组织中均表现出每日节律性。此外，类固醇生成转录本显示出与树麻雀（Passer montanus）年度繁殖周期相对应的季节性变化。
