Study On Selection Pressure Of Four Color Related Genes And Gowth Combining Effects Of The Two Patterns In Oujiang Color Common Carp

Oujiang Color Common Carp( Cyprinus carpio var. color), with more than 1200-year-old breeding history, mainly has 5 kinds of basic body color patterns, namely “whole red”, “whole red with big black spots”, “whole red with small black spots”, “whole white” and “whole white with big black spots”. Since 1999, the carp has been conducted many generations of artificial breeding, forming the relatively stable body color and obvious genetic differences, which has been in long-term natural selection and short-term high-strength artificial selection.To understand selection(including natural and artificial selection) pressure on body color related genes and the differences, in this study, the breeding lines of Oujiang color common carp were used to analysis the selective pressure on the key gene(Tyr), the important genes(Tyrp1 and Dct) and the regulated gene(Sox10) of melanin synthesis pathway, and discuss the selective pressure differences between the carp with black spot and the carp without black spot.Then, the carps without black spot(“whole red” and “whole white”) were used to discuss the combination effects and breeding performance between different body color.More details are presented as follows: 1 Selection pressure analysis on the key gene(Tyr) of melanin synthesis pathway in Oujiang Color Common CarpIn this study, the total of the fifth generations of Oujiang color common carp(F5) were used to observe the variation and selection pressure sensitivity of tyrosinase(TYR) gene among the five exons in this gene and among the five body color patterns in this fish. The results showed: the nucleotide variation rate and the number of their positive selection sites in exon 1 and exon 5 were higher than those of the other three exons, indicating these two exons were moreeasily subjected to selective pressure. The ratios(ω) of dN / dS of the five exons were all less than 1(0.10-0.67), which demonstrated there were purifying selection conducted in tyrosinase gene. Similarly, the ratio(ω=0.12-0.23) illustrated there were also purifying selection in the five body color patterns of Oujiang color common carp. The amino acid site analysis of selection pressure using the Codeml models(M2a and M8) in the software PAML indicated that there were more positive selection sites in the fish without black spots than the fish with black spots, although there were no significant difference(P>0.05). Furthermore, some amino acid sites were also found with more easily positive selection than the other acids in tyrosinase gene. The results primarily showed that, tyrosinase gene was conservative in evolutionary process and mainly subjected to purifying selection in Oujiang color common carp, and no significant selection pressure on this gene were found under artificial selection on this fish. 2 Selection pressure analysis on the eumelanin biosynthesis related genes(Tyrp1 and Dct) in Oujiang Color Common CarpIn this study, the breeding lines of Oujiang color common carp(F8) were used to observe the expression differences, the sequence genetic variations, and selective pressure differences of eumelanin biosynthesis pathway genes(Tyrp1 and Dct). The results showed: Tyrp1(including Tyrp1 a and Tyrp1b) only expressed in tissues containing melanin(such as eyes, the black skin in “whole red with big black spots”), and no expression were found in tissues without melanin(such as the red skin in “whole red” and “whole red with big black spots”); There were no significant differences in sequence genetic variations between the fish with black spots and the fish without black spots, and mainly subjected to purifying selection(ω=0.20-0.80). The amino acid site analysis of selection pressure using the Codeml models(M2a and M8) in the software PAML indicated that there were no significant positive selection sites of Tyrp1 in the fish, but different from Tyrp1, Dct gene were detected significant positive selection sites in the fish.Generally, the eumelanin biosynthesis pathway genes were conservative and mainly subjected to purifying selection. The artificial breeding has effected the evolution of different color patterns of Oujiang color common carp, while caused the difference among the driven effects of eumelanin synthesis pathway genes. 3 Selection pressure analysis on the regulated gene(Sox10) of melanin synthesis pathway in Oujiang Color Common CarpIn this study, the breeding lines of Oujiang color common carp(F8) were used to discuss the sequence differences and selective pressure differences of melanin synthesis pathway regulated gene(Sox10). The results showed: there was a non synonymous mutation site of SNP in the 41 st amino acid site in the coding region of the gene between the fish with black spots and the fish without black spots, that was to say, the amino acid of this site was Phe in the fish with black spots, while Ser in the fish without black spots; besides, the genetic diversity index in the fish with black spots was higher than the fish without black spots. The amino acid site analysis of selection pressure using the Codeml models(M2a and M8) in the software PAML indicated that there were differences among the detected positive selection sites between the fish with black spots and the fish without black spots, but with no significant differences, which indicated the divern effects to regulated gene was not obvious. 4 Studies on growth combination effects in “whole red” and “whole white”color patterns of Cyprinus carpio var. color.In this study, the breeding lines of “whole red” and “whole white”color patterns of Oujiang color common carp(F8) were used in analyzing the combination effect, such as mean value, CV, GCA,SCA and heterosis of each growth traits of the one year old and two-year old stage in F1 hybrids through complete diallel cross(containing 4 combinations). The results showed: as improving the genetic purity of breeding lines, artificial selection could benefit the complete set line breeding. Using the high purity body color “whole red” and “whole white”color patterns of Oujiang color common carp to carry out the complete set of breeding, could achieve good combination effect; “whole red” and “whole white” combination, especially the combination of “whole white” ♀דwhole red”♂could be used as a good combination for breeding.To sum up, the genes of melanin synthesis pathway are conservative, mainly by purifying selection. Under the effect of artificial selection, hybridizing the high purity body color“whole red” and “whole white”color patterns of Oujiang color common carp hybridization can achieve good combination effects.