SNP detection of GnRH-1 gene
PCR amplification products of GnRH-1 gene in China yellow quail, Beijing white quail and Korean quail were shown in Fig 1. Clearly, the amplification fragments of GnRH-1 gene gave high-definition bright bands near 900bp, which conformed to the target size of 906bp. Totally 14 SNP mutation sites of GnRH-1 gene were detected in three egg quail species, which were C71T, C108T, C168T, C178T, A184G, C206T, A209C, C215T, A252G, A279T, C281T, C293G, C339T and C458T respectively (Fig 2).
GnRH-1 polymorphism of quail, they detected 6 mutation sites, including C108T, C168T, C178T, A184G, C206T and C215T, only C108T was silent mutation without causing change to corresponding amino acid (Pu, 2016). In this study, 8 additional mutation sites were detected, which were C71T, A209C, A252G, A279T, C281T, C293G, C339T and C458T, demonstrating that GnRH-1 gene had rich polymorphism in 3 egg quail species.
Association analysis between GnRH gene and carcass traits
It could be seen from Table 1 that body weight, dressed carcass weight, whole net carcass weight and liver weight of AA and AC genotypes of A209C were significantly higher than those of CC genotype (
P<0.05), while no significant differences were observed between AA and AC genotypes in term of the indexes above (
P>0.05). Moreover, dressing percentage of AA genotype of A209C was significantly higher than that of AC and CC genotype (
P<0.05), but no significant difference was observed between AC and CC genotypes (
P>0.05). For C215T, breast muscle weight (whole) of CT genotype was far higher than that of TT genotype (
P<0.05), but breast muscle weights (whole) of CT and TT genotypes were similar with that of CC genotype (
P>0.05). For A279T, breast muscle weights (whole) of TT was far higher than that of AT genotype (
P<0.05). For C281T, Liver weight of CC genotype was far higher than that of TT genotype (
P<0.05), but no significant difference was observed between CC, TT and CT genotypes (
P>0.05). For C281T, dressing percentage of CC genotype was significantly higher than those of CT and TT genotype (
P<0.05), but no significant difference was observed between CT and TT genotypes (
P>0.05). For C339T, liver weight of TT genotype was far higher than that of CC genotype (
P<0.05), but CT genotype showed no significant difference with TT and CC genotypes (
P>0.05). For C339T, dressing percentage of TT genotype was far higher than those of CC and CT genotypes (
P<0.05), but no significant difference was observed between CC and CT genotypes (
P>0.05).
The association between GnRH receptor gene polymorphism and testicular parameters, and found that GnRH receptor gene was significantly correlated with testicular length (TL) (
P<0.05)
(Iyer et al., 2019). The kisspeptin (KiSS)/GnRH1 system was expressed in horse Leydig cells and modulated their endocrine activity
(Petrucci et al., 2020). That VAL-opsin not only affected activity of the HPG axis but also acted on the pituitary gland to directly stimulate a new sexual maturation pathway that promoted the secretion of GTHs independent of GnRH in goldfish
(Choi et al., 2020). There existed a remarkable association between the SNPs of GnRH and sperm quality traits of Chinese water buffalo
(Wang et al., 2020). A highly significant association between G840327C of GnRH-I gene and age at first egg (AFE) in a Chinese chicken population (
P<0.01) (Xu
et al., 2011a). For mutation site T68G of GnRH gene detected in Rongjiang little sweet sheep, lambing number of GG genotype was far higher than those of the rest two genotypes (
P<0.05)
(Li et al., 2016). That 3 SNPs of GnRH gene influenced laying start age of Erlangshan chicken significantly and SNP5 played an important role in body weight at beginning of laying
(Hu et al., 2015). All These studies showed that GnRH gene could regulate the production performance of poultry. In this study, five SNPs including A209C, C215T, A279T, C281T and C293G of GnRH-1 gene were significantly correlated with the breast muscle weight (whole), liver weight, dressing percentage, body weight, dressed carcass weight and whole net carcassweight of quail (
P<0.05), which supported the studies mentioned above.