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The tyrosinase (TYR) and melanocortin 1 receptor (MC1R) genes have been accepted as major genes involved in the plumage pigmentation of chickens. The co-segregation of plumage coloration and sequence polymorphism in TYR and MC1R genes were investigated using an intercross between black and white plumage color types of the Dongxiang blue-shelled chicken. Profiles of plumage color changing and genes expression levels of TYR and MC1R were observed from hatch to 112 d of age using quantitative real-time reverse transcription-PCR. Intercrossed offspring were classified by phenotypes of plumage colors. The phenotypes of black and amber chicks with genotypes of E̱C̱ exhibited a black feather pattern, whereas white, gray, and buff chicks with genotypes of E̱cc and eecc belonged to the white feather pattern. Although TYR in cooperation with MC1R determined the coloration feather patterns, the different phenotypes did not correspond completely with the genotypes. During the period studied, plumage phenotype changed dramatically, and the buff and gray down were gradually replaced by whiteness feathers. Real-time reverse transcriptionPCR studies showed that 1) expression levels of TYR declined dramatically with age, and expression at hatch was highest (P < 0.01) during the ages studied; 2) expression level of MC1R was higher at 28 d than at younger and older ages; and 3) expression of TYR in chickens carrying E/E and E/e alleles on MC1R loci were higher than those carrying e/e alleles from hatch to 28 d. [ABSTRACT FROM AUTHOR]

Toll-like receptors (TLR) are trans-membrane sensors recognizing invading microbes. Toll-like receptors play a central role in initiating immune responses against several pathogens. In this study, we investigated the response of TLR and downstream genes to Marek's disease virus (MDV) infection. Forty 1-d-old chicks were randomly divided into 2 groups, with 20 chicks infected with MDV and 20 chicks mock-infected. Four chickens were euthanized respectively from infected and age-matched noninfected groups at 4, 7, 14, 21. and 28 d postinfection (dpi). Bursas, spleens, and thymuses were removed. The differential expression of TLR genes, including TLR3, TLR5, TLR7, TLR15, and TLR21, and downstream genes of TLR 7, including MyD88, TRAF3, TRAF6, IFNA, IFNB, and IL6, in lymphoid tissues of MDV-infected and noninfected chickens was determined by real-time PCR. The results showed that the change of TLR genes was different in 3 lymphoid tissues. Expression of TLR7 and MyD88 was upregulated at 14 dpi and downregulated at 28 dpi in MDV-infected compared with noninfected spleens. The TRAF6 and IFNB were upregulated, and TRAF3, IFNA, and IL6 genes showed increasing trends in MDVinfected compared with noninfected spleens at 14 dpi. The expression of TLR3 and TLR 15 genes was downregulated in MDV-infected compared with noninfected spleens at 28 dpi. The results indicated that TLR7 and its downstream genes were a response to MDV infection at 14 dpi. However, the function of TLR was impaired when the infection entered the tumor transformation phase. In bursas, TLR3 and TLR 15 genes were upregulated at 7 and 4 dpi, respectively. It indicated that TLR3 and TLR 15 might be involved in response to MDV infection in bursa at early phases. However, no differential expression of TLR genes was observed between MDV-infected and noninfected thymuses, which indicated that the thymus had little response to MDV infection mediated by TLR. [ABSTRACT FROM AUTHOR]