Characteristics of Reversion to Early Feathering Phenotype in the Late Feathering Line of Nagoya Breed Chickens

摘要

It has been found that female progeny with the early feathering (EF) phenotype rarely emerge in late feathering (LF) strains of chickens. However, few detailed studies on the incidence of reversion have been reported. The present study was conducted to examine the incidence of reversion across three generations (G7-G9) in an LF line of the Nagoya breed and to investigate the characteristics of DNA structures of the revertant EF females. A total of five EF revertant females were observed (G7: 3 out of 376, G8: 1 out of 383, G9: 1 out of 411), and the incidences observed in G7, G8, and G9 were 0.80, 0.26, and 0.24%, respectively. Results of two PCR and one RFLP-PCR analyses indicated that there were two types of EF revertants in the Nagoya breed (3 birds were Type I and 2 birds were Type II), and that the reversion to the EF phenotype might be accompanied by the loss of either an OR (occupied repeat) or a UR- K region (unoccupied repeat on the K locus), which were homologous DNA regions produced by insertion of an avian endogenous virus gene ( ev 21) and duplication. Moreover, phenotypes of full-sib and half-sib sisters of the EF revertants confirmed that the sires of the EF revertants have never harbored excision of either OR or UR- K at the ev 21- K complex locus on one of two Z chromosomes, suggesting that the reversion event occurred in spermatogenesis.