Expression and comparison of growth gene (IGF-1) in native and non-native rainbow trout (Oncorhynchus mykiss) in three different sizes

Fish growth is regulated by many environmental and physiological factors and is shaped by the genetic background of each organism. Insulin-like growth factor I (IGF-I) plays an important role in various biological processes of fish. This study aimed to examine the rate of expression of IGF-I mRNA growth gene at different stages of growth in local and imported rainbow trout in Iran.

Hence, local and imported trout fish in three sizes of small, medium and large, with a total mean weight and size of 453.66±244.34 gr and 32.25±6.78 cm, respectively, were obtained from the fish breeding center in Guilan province (Rasht). First, 20 mg samples of the liver tissue of the fish were obtained under sterile conditions after anesthesia from both local and imported breeds. RNA extraction and cDNA synthesis were performed according to the RT-PCR standard method in the Genetics Research Laboratory of Tonekabon Azad University.

The results showed that the expression of IGF-I gene was significantly different between local and imported breeds so that the highest and lowest gene levels were in the small size of imported breed and medium size of local breed, respectively (P<0.05). However, there was no significant relationship between the amount of gene expression and weight and length of fish (P˃0.05), while IGF-I expression showed a decreasing trend with an increase in the fish size.

These findings suggest that the IGF-I gene may play a key role in the growth and development of rainbow trout.