Abstract
In the present study, polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and restriction fragment length polymorphism (RFLP) methods were compared to analyze the polymorphism of growth hormone receptor (GHR) gene in French, Iranian and Danish strains of Oncorhynchus mykiss. A monomorphic SSCP pattern of AA genotype in the French and Iranian strains and a dimorphic AA and AB genotype in the Danish strain were observed in 3' non-coding regions of GHR gene. In the Danish strain, the AB genotype polymorphism of the GHR gene with its very low frequency (5%) has no effect on the production trait. While, RFLP-Dde1 showed no polymorphism with genetic variation in the location of GHR. Moreover, comparing the condition factors (K) of three different rainbow trout strains showed a significant correlation between the French (1.312 ± 0.13), Iranian (1.245 ± 0.17) and Danish strains (0.763 ± 0.1), respectively (p<0.05). In particular, the French strain obtained a higher K compared to the two others. The length-weight relationship is shown by the following equations W= 0.013 × L2.921, W= 0.012 ×L3.023 and W= 0.007 × L3.176 for French, Iranian and Danish strains, respectively. With the mean (b= 2.921), the studied French strain exhibited a negative allometric growth b<3 while the Iranian (b=3.023) and the Danish (b=3.176) showed positive allometric growths. Regardless of the underlying mechanism(s) responsible for the different relationships, the results of this study suggested that the AA and AB genotypes polymorphism of the GHR gene are not associated with condition factor and environmental variables can influence condition factor and length-weight relationship of rainbow trout strains in this study.
Highlights
Hormones, growth factors, and other regulatory proteins associated with the so-called “somatotropic axis” are candidate markers for quantitative trait in farm animals [1]
188 bp of Growth hormone receptor (GHR) was amplified from nucleotide 285 to nucleotide 473 through the use of PCR-Single-Stranded Conformation Polymorphism (SSCP) method (Figure 1)
RFLPDde1 showed no polymorphism with genetic variation in the location of GHR (Table 1)
Summary
Growth factors, and other regulatory proteins associated with the so-called “somatotropic axis” are candidate markers for quantitative trait in farm animals [1]. GHR mediates the biological actions of GH on target cells by transducing the GH stimulating signal across the cell membrane and subsequently inducing the transcription of many genes, including IGF-I [5]. There are few studies on GHR in fish, in Atlantic salmon GHR appears to play a similar role within the somatotropic axis as in humans and its differential expression is what mediates the cellular response to GH plasma levels, and in particular the production of IGF [6]. Significant associations have been observed between GHR gene polymorphism and growth rates by PCR restriction fragment polymorphism (RFLP) marker (using four restriction enzymes) in 353 individual Cyprinus carpio fish [10]
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