Abstract:

This study was designed to explore characteristics of genetics, mechanism of occurrence and disappearance of poultry piRNAs, and accumulate basic materials for research about birds small RNA-binding protein and practical application. 19 pilRNAs sized 23-39 nt were discovered by constructing cDNA library of small RNAs, TA cloning and sequencing in chicken testicular tissue. According to size, homology and secondary structure, 3 different sequences were selected for analyzing temporal and spatial expression of pilRNAs by using Q-PCR technology in different tissues at different growth and development stages of Rugao chicken and Recessive White Feather chicken. The result showed that, consistent with other species, distribution of pilRNA-encoding sequences in the chicken genome was found to be asymmetrical on chromosomes, meanwhile, displayed a preference for intergenic regions across genome. Unlike the secondary structure of miRNAs, pilRNAs were predicted an unique stem-loop secondary structure. Chicken pilRNAs were not only abundant in germline tissue, but also abundant in other tissues, and expression at mRNA level was influenced mainly by different pilRNAs, breeds and gender. The expression level of gga-piR-1 was the lowest in all tissues of two breeds and reached the consistent trend at week 12, while gga-piR-4 showed moderate expression levels. gga-piR-5 revealed the highest and moderate levels in all tissues of the male Rugao chicken and Recessive White Feather chicken, respectively and they were up to peak at week 8 for the male Rugao chicken, whereas it expressed moderately in female of both breeds. Therefore, the difference of the secondary structures between pilRNAs and miRNAs indicate that the difference in splicing and processing mechanisms of two small RNAs, pilRNAs may not only be confined to development and maintenance for germline tissue, but also play important roles in somatic tissues and different pilRNAs may be involved in different regulatory function in the complex biological processes.