Oviductal expression of avidin, avidin-related protein-2, and progesterone receptor in turkey hens in relation to sperm storage: effects of oviduct tissue type, sperm presence, and turkey line.

The sperm storage tubules (SST) of the turkey hen, which are located in the uterovaginal junction (UVJ) of the oviduct, maintain viable sperm for up to 10 wk after a single insemination. The mechanisms of this in vivo sperm storage are poorly understood. Our objective was to evaluate mRNA and protein expression of avidin and 2 avidin-associated factors, avidin-related protein-2 (AVR2) and progesterone receptor, in the oviducts of 2 different lines to determine the extent to which they were sperm responsive and tissue specific. At 38 wk of age, Hybrid Grade Maker and Converter turkey hens were artificially inseminated with diluted semen (AI) or were sham-inseminated with extender alone (SI). Forty-eight hours after insemination, total RNA was extracted from the UVJ epithelium (containing SST) and vaginal epithelium (VGE) of SI and AI hens. Real time-polymerase chain reaction data showed a clear tissue region-specific effect on gene expression in the turkey hen oviduct, with much greater (P < 0.0001) expression in the UVJ compared with VGE region for avidin and AVR2 mRNA in both lines and for progesterone receptor mRNA in the Converter line. In contrast to real-time PCR data, in situ hybridization of SI and AI tissues showed that the presence of sperm increased avidin mRNA in the SST and UVJ surface epithelium in the Converter hens. Immunohistochemistry confirmed the presence of avidin protein in the epithelium of the UVJ in both lines; however, whereas avidin protein was localized in the SST of SI-Grade Maker hens, this protein was not detected in the SST of Converter hens. The upregulation of avidin and AVR2 mRNA within the sperm storage region indicates the involvement of avidin, and perhaps avidin analogs, in the sustained storage of sperm in the SST, possibly through the binding of biotin to avidin. The absence of avidin protein in the SST and VGE of Converter hens in the presence of increased mRNA may indicate a rapid turnover of protein.