Real-time quantitative (PCR) applications to quantify and the expression profiles of heat shock protein (HSP70) genes in Nile tilapia, Oreochromis niloticus (L.) and Oreochromis mossambicus (P.)

Abstract

Quantitative real-time PCR (qRT-PCR) has already been used to study the expression profiles of heat 
shock protein (Hsp) genes in Nile tilapia, Oreochromis niloticus (Lineaus, 1752) and Oreochromis 
mossambicu (Peter, 1983). Young fish were exposed to heat stress for 5.5 h followed by qRT-PCR of 
Hsp70 mRNA, using tubulin (tub) as a reference gene and flourogenic dyes. Expression of Hsp70 mRNA 
peaked at 1 h of heat stress and decreased at 5.5 h. This method proved to be a very sensitive 
technique in quantifying Hsp70 transcripts in 6.70 ng of total DNA from the two tilapia species. A 
standard curve was prepared, for both tilapia fishes showed almost uniform results throughout the 
experiment. The threshold PCR cycle (Ct), at which RT -PCR products from DNA standards 
accumulated to a critical level, was determined for samples in the range of 2 × 104 to 2 × 1010 
molecules/ l. From conclusion of this study, it is shown that when the tilapia fish muscles are subjected 
to stress, with the help of abiotic factors- temperatures, whether above or below optimum condition 
within a stipulated period of time in a peculiar way, will lead to the production of the Hsp70 protein