Gene and hormones involved in stress density and immunity response of G6 transgenic mutiara catfish (Clarias gariepinus)

A stocking density difference test (30, 60, and 90 fish/400 L) and gene expression analysis of Clarias gariepinus growth hormone ( CgGH ), thyroid hormone receptor ( THR ), heat shock protein 70 ( HSP70 ), toll-like receptor-1 ( TLR1 ), and immunoglobulin M ( IgM ) using QRT-PCR and ELISA for cortisol ( COR ) and IgM levels were used to assess the immunity of G6 transgenic ( TG ) mutiara catfish that were two months old. TG fish are treated with density treatments A (30 fish/400 L), B (60 fish/400 L), and C (90 fish/400 L), while non-transgenic ( NTG ) fish are treated with A* (30 fish/400 L), B* (60 fish/400 L), and C* (90 fish/400 L) for 60 days of rearing with six replications. The CgGH , THR , HSP70 , TLR1 , and IgM genes were more highly expressed in TG fish with high density (90 fish/400 L) (means 4.75 ± 0.78; 5.09 ± 0.92; 4.76 ± 0.79; 17.79 ± 0.67; 15.22 ± 0.63) than in low density (30 fish/400 L) (means 2.12 ± 0.60; 1.68 ± 0.75; 3.55 ± 0.75; 6.92 ± 0.57; 3.53 ± 0.92) and NTG fish (means 0; 0.89 ± 0.48; 2.12 ± 0.63; 2.40 ± 0.46; 2.00 ± 0.60). CgGH modulates the expression of THR and HSP70 genes and increases the expression of TLR1 and IgM , suggesting that GH –transgenesis may enhance fish immunity to stress in high stocking density. After 60 days of high-density treatment, NTG fish had higher white blood cell counts (means 46.20 ± 1.00 × 10 3 cells/mm 3 ) and COR levels (means 69 ± 1.94 ng/mL) than TG fish (means 36.70 ± 1.01 × 10 3 cells/mm 3 and 38.65 ± 1.43 ng/mL), suggesting that NTG fish are more easily stressed. The function of CgGH in TG fish at the ideal stocking density (60 fish/400 L) can shield the kidneys from glomerular necrosis or renal tubular hypertrophy, as demonstrated in NTG fish, according to kidney histology. Thus, a research goal is to determine how genes and hormones involved in stress and immunity induction relate to fish density in transgenic and non-transgenic fish.