Acharjee A, Chaube R, Joy K P
Department of Zoology, Banaras Hindu University, Varanasi, 211005, Uttar Pradesh, India.
J Fish Biol. 2017 Jun;90(6):2289-2311. doi: 10.1111/jfb.13305. Epub 2017 Apr 9.
Differential effects of photoperiod and temperature on the temporal modulation of gonadotrophin subunit genes (glycoprotein α, gpα), follicle-stimulating hormone β (fshβ) and luteinizing hormone β (lhβ) expression were investigated in the stinging catfish Heteropneustes fossilis. Female H. fossilis were exposed to varying photoperiod and temperature conditions for 14 and 28 days in the early preparatory phase of the annual reproductive cycle. Gonadotrophin subunit gene expression, gonado-somatic index (I ), ovarian histology and plasma steroid hormone levels were evaluated. The exposure of H. fossilis to long photoperiod (LP) of 16 h light or high temperature (HT) at 28 ± 2° C (mean ± s.e.), alone or in combination, resulted in significant increases in gpα, fshβ and lhβ messenger (m)RNA levels, I , plasma oestradiol-17β (E ), testosterone (T) and progesterone (P ) levels. The ovaries were filled with advanced yolky oocytes. On the other hand, the short photoperiod (SP) of 8 h light exposure decreased the transcript levels with higher inhibition in the normal temperature (NT) group at 18 ± 2° C (mean ± s.e.) than the HT group at 28 ± 2° C. Furthermore, the inhibition reached the highest level in total darkness (TD) of 24 h light deprivation under NT conditions at 18 ± 2° C. Consequently, the SP and TD treatments inhibited the I , plasma E and T levels and ovarian development. The exposure to high temperature at 28 ± 2° C also modified the short photoperiod effect by elevating plasma E level. The plasma T level changed only mildly while the plasma P level showed the greatest fluctuations; the level reached the nadir in the SP + HT group but increased in the SP + NT group on day 28. A two-way ANOVA of the data showed differential effects of photoperiod and temperature; photoperiod produced a highly significant effect on fshβ expression while temperature had a highly significant effect both on lhβ and gpα levels. Thus, the differential expression of the gpα by the environmental variables ensures temporal synchronization of ovarian development and spawning.
研究了光周期和温度对鲇形目鲇科鱼类（Heteropneustes fossilis）促性腺激素亚基基因（糖蛋白α，gpα）、促卵泡激素β（fshβ）和促黄体生成素β（lhβ）表达的时间调节的差异影响。在年度繁殖周期的早期准备阶段，将雌性H. fossilis暴露于不同的光周期和温度条件下14天和28天。评估促性腺激素亚基基因表达、性腺-体指数（I）、卵巢组织学和血浆类固醇激素水平。将H. fossilis单独或联合暴露于16小时光照的长光周期（LP）或28±2°C（平均值±标准误）的高温（HT）下，导致gpα、fshβ和lhβ信使（m）RNA水平、I、血浆雌二醇-17β（E）、睾酮（T）和孕酮（P）水平显著升高。卵巢充满了晚期卵黄卵母细胞。另一方面，8小时光照的短光周期（SP）降低了转录水平，在18±2°C（平均值±标准误）的常温（NT）组中比28±2°C的HT组受到更高的抑制。此外，在18±2°C的NT条件下，24小时光照剥夺的完全黑暗（TD）中抑制达到最高水平。因此，SP和TD处理抑制了I、血浆E和T水平以及卵巢发育。暴露于28±2°C的高温也通过提高血浆E水平改变了短光周期效应。血浆T水平仅轻微变化，而血浆P水平波动最大；在第28天，该水平在SP+HT组中达到最低点，但在SP+NT组中升高。对数据进行的双向方差分析显示光周期和温度的差异影响；光周期对fshβ表达产生高度显著影响，而温度对lhβ和gpα水平均产生高度显著影响。因此，环境变量对gpα的差异表达确保了卵巢发育和产卵的时间同步。
