Impact of Temperature Upon Expression Levels of Thrr, Gnrhr, and Fshr Leading to Gonadal Maturation of G5 Transgenicmutiara Strain Female Catfish (Clarias Gariepinus)

Abstract

This study aims to determine the impact of temperature upon the relative expression ratio of thyroid hormone receptor (THRr), gonadotrophin-releasing hormone receptor (GnRHr), follicle stimulating hormone receptor (FSHr) and ꞵ-actin genes as internal control expression in transgenic G5 mutiara female catfish and non-transgenic catfish using real-time PCR. In addition, the expression of growth hormone (GH) and estradiol (E2) levels which both induced gonadal growth was further observed. The temperature treatment (A: 22°C; B: 26°C; C: 30°C for transgenic fish; and A*: 22°C; B*: 26°C; C*: 30°C for non-transgenic fish) were designed with 6 replicates (n = 6) during a 60-day rearing period. A warm temperature (26°C) was the optimum temperature that induced THRr, GnRHr, FSHr gene expressions (means, 3.40 ± 0.69, 4.23 ± 0.62, 7.25 ± 0.43 respectively) and induced higher GH (means, 6.13 ± 0.78 ng/ml) and E2 (means 5.78 ± 1.05 ng/ml) levels leading to an increase in transgenic ovary weight (means, 59.90 ± 2.20 g) in transgenic fish higher than non-transgenic. Meanwhile, low temperature (22°C) and high temperature (30°C) caused a decrease in the expression levels of THRr, GnRHr, FSHr for transgenic fish and for non-transgenic fish. The presence of CgGH in G5 transgenic catfish was able to maintain adequate GH levels and has the potential to stimulate the growth of female gonads at high temperatures (30°C).