Abstract
Nutritional and medicinal benefits have been attributed to the consumption of tissues from the black-boned chickens in oriental countries. Lueyang black-boned chicken is one of the native chicken breeds. However, some birds may instead have white or lighter skin, which directly causes economic losses every year. Previous studies of pigmentation have focused on a number of genes that may play important roles in coat color regulation. Illumina2000 sequencing technology was used to catalog the global gene expression profiles in the skin of the Lueyang chicken with white versus black skin. A total of 18,608 unigenes were assembled from the reads obtained from the skin of the white and black chickens. A total of 649 known genes were differentially expressed in the black versus white chickens, with 314 genes that were up regulated and 335 genes that were down-regulated, and a total of 162 novel genes were differentially expressed in the black versus white chickens, consisting of 73 genes that were up-regulated (including 4 highly expressed genes that were expressed exclusively in the skin of the black chickens) and 89 genes that were down-regulated. There were also a total of 8 known coat-color genes expressed in previous studies (ASIP, TYR, KIT, TYRP1, OCA2, KITLG, MITF and MC1R). In this study, 4 of which showed greater expression in the black chickens, and several were up-regulated, such as KIT, ASIP, TYR and OCA2. To our surprise, KITLG, MITF and MC1R showed no significant difference in expression between the black- and white-skinned chickens, and the expression of TYRP1 was not detected in either skin color. The expression of ASIP, TYR, KIT, TYRP1, OCA2, KITLG, MITF and MC1R was validated by real-time quantitative polymerase chain reaction (qPCR), and the results of the qPCR were consistent with the RNA-seq. This study provides several candidate genes that may be associated with the development of black versus white skin. More importantly, the fact that the MC1R gene showed no significant difference in expression between the black and white chickens is of particular interest for future studies that aim to elucidate its functional role in the regulation of skin color.
Highlights
The skin color of chickens is an important economic trait
Information regarding the primers of Melanocortin-1 receptor (MC1R), TYR, KIT, agouti signaling protein (ASIP), TYRP1, Oculocutaneous albinism type 2 (OCA2), KITLG, MITF used for the quantitative polymerase chain reaction (qPCR) can be found in Table 1. β-actin was used as housekeeping gene
The results indicated that there were no significant differences in the expression of MC1R, KITLG and MITF between the black and white skin samples (Fig 4), but the expression of TYR, KIT, OCA2 and ASIP was significant (P value < = 0.05); the results of the qPCR were consistent with the RNA-seq
Summary
The skin color of chickens is an important economic trait. There are three skin colors found in chickens: white, yellow and black. Skin color is the most direct marker whether the bird is black-bone chicken or not. The Lueyang black-boned chicken is one of the native chicken breeds of Lueyang County in the Shaanxi Province of China. This bird is typically composed of eight characteristic black parts: feathers, wing tips, beak, cockscomb, skin, bones, legs and claws. Some birds may instead have white or lighter skin, which directly affects the selective breeding of the Lueyang chicken population and causes economic losses every year. The presence of pigmented skin among Lueyang chickens is significantly tied to their economic value and the speed of breeding
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