Abstract
ABSTRACT Homeobox B9 (HOXB9) gene has been demonstrated to be associated with melanogenesis in chicken plumage by high-throughput RNA sequencing. In this study, we cloned and characterised HOXB9 in black-boned chickens. Two alternative splice variants (HOXB9-1 and HOXB9-2) were identified in chicken feather bulbs. Expression analysis of HOXB9 in 11 different chicken tissues by RT-PCR indicated that the two transcripts were only expressed in the kidney, abdominal fat, feather bulbs, skin, and small intestine. No HOXB9-1 or HOXB9-2 transcripts were detected in the breast muscle or the ovary. The two HOXB9 variants were expressed at significantly different levels in black feather bulbs and white feather bulbs (p<0.01), and in black skin compared with white skin (p<0.01). The results indicate that HOXB9-1 and HOXB9-2 may be involved in melanin formation in the plumage and skin. The expression of HOXB9-2 was higher in white than in black muscles (p<0.05), HOXB9-2 may play a role in muscle melanogenesis. Our results suggest that HOXB9, which is partially regulated by alternative splicing, may be involved in the process of melanogenesis in the black-boned chicken.
Highlights
Black-boned chickens demonstrate intense pigmentation of their tissues, including the skin, muscle, feathers, claws, gonads, periosteum, and mesentery (Faraco et al, 2001; Dorshorst et al, 2011; Yu et al, 2017)
Two PCR products of different lengths were obtained from black feather bulbs (Figure 2), suggesting that the chicken Homeobox B9 (HOXB9) gene may have two alternative splice variants, HOXB9-1 (GenBank accession number: MH048960) and HOXB9-2 (GenBank accession number: MH048961)
The highest expression levels of HOXB9-1 and HOXB9-2 were detected in the kidney, abdominal fat, feather bulbs, skin, and small intestine
Summary
Black-boned chickens demonstrate intense pigmentation (hyperpigmentation or fibromelanosis) of their tissues, including the skin, muscle, feathers, claws, gonads, periosteum, and mesentery (Faraco et al, 2001; Dorshorst et al, 2011; Yu et al, 2017). Skin, and muscle pigmentation phenotypes are important economic traits in black-boned chicken production, as chickens with black feathers, skin, and muscles are generally considered to have superior nutritional and medicinal properties (Tian et al, 2007). Melanin-based pigmentation is a major component of chicken feather, skin, and muscle colouration that is often under strong genetic control (Bourgeois et al, 2016). More than 150 body colour-associated genes have been found to play wellknown roles in pigmentation (Cieslak et al, 2011). Further exploration of other candidate genes using different techniques may be required to elucidate the complex molecular mechanisms of melanin pigmentation
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