Differential Analysis of Tissue Expression of GnRHR2 mRNA in Gaoyou and Jinding Duck Breeds

The objective of this study was to clone the sequence of Duck GnRHR gene and knowledge of its function in reproduction.RT-PCR method was used to clone GnRHR cDNA from duck reproductive tissues,and its expression levels during early laying days and laying fastigium period between Gaoyou and Jinding duck breeds were tested by Real-time PCR.Sequencing and homology analysis showed the cloned duck GnRHR cDNA was about 500bp in length,and it belonged to the avian type II GnRHR isoforms.It was 96% identical to the cGnRHR2 sequence reported in domestic chicken.Compared to Gaoyou duck,the first laying age of Jinding duck predated 30 days,the production exceed 83 eggs.Real-time PCR results indicated expression levels of GnRHR2 increased in pituitary and hypothalamus,but decreased in ovary from early laying days to laying fastigium period.A pronounced breed difference existed,with higher expression levels(P0.05,P0.01) in Gaoyou duck pituitary and hypothalamus.In contrast,higher expression levels(P0.01)occurred in Jinding duck.It suggested that the short-lived higher expression of ovary GnRHR2 gene before early laying days was necessary for the onset of sexual maturation,and the upregulation in pituitary and hypothalamus after early laying days could aid to keep laying fastigium.