Genomic mapping and comparative genomics of candidate loci
regions
The candidate loci that we identified were located in intronic regions
of the following genes. The loci 602-G/C is in one of the introns of the
gene FAM135A (DUF676 domain-containing protein), a relatively
unknown domain with GO-slim terms annotation related to cellular
metabolic processes with putative lipase activity and QTLs associated
with regulation of fat intramuscular deposition in chickens and cattle
breeds (Poleti et al., 2018; Yuan et al., 2022). This section of our
contig 602 is apparently orthologous to a similar region on theGallus gallus chromosome 3, and a region conserved across other
bird taxa. The loci 3657-C/T was found within the gene
formimidoyltransferase cyclodeaminase (FTCD ) and flanked by a
feather β-keratin (BISK1) and collagen alpha-2(chain VI)
(ColA62 ) (Fig. 2). The FTCD is a single copy gene coding
for a key component of the folate metabolism (Wernimont et al., 2011).
It also expresses a bifunctional enzyme involved in starvation-induce
responses by downregulating the mTORC1 pathway towards the maintenance
of homeostasis under low resource conditions (Zhang et al., 2021). While
this region is also in synteny among other bird taxa (with theColA62 + FTCD clustering in the same orientation), theBISK1 is a relatively recently discovered copy of a β-keratin
identified primarily in chicken but present also in blue and great tit
genomes (Fig. 2). The novelty falls on BISK1 , a recently
identified β-keratin found to be expressed only in cells defining
pennaceous barbules in the contour feathers of chickens (Kowata et al.,
2014).