The honeybee, Apis cerana cerana (Ac), is an important pollinator and has adapted to the local ecological environment with relevant coloration. The cuticle coloration of the brown (br) mutant is brown instead of black in wild-type individuals. Therefore, this study aimed to identify and characterize the gene responsible for the br mutation. Genome resequencing with allele segregation measurement using Euclidean distance followed by Lowess regression analysis revealed that the color locus linked to the mutation was located on chromosome 11. A 2-base deletion on exon 4 was identified in the g7628 (yellow) gene after genome assembly and sequence cloning. In addition, the cuticle color of the abdomen of worker bees changed from black to brown when a defect was induced in the yellow gene using short interfering RNA (siRNA); however, the survival rate did not decrease significantly. These results indicate that the yellow gene participated in the body pigmentation, and its defect was responsible for the br mutation. This study promotes the understanding of the molecular basis of body coloration in honeybees, enriching the molecular mechanisms underlying insect pigmentation.

In this study, we report evidence of a novel duplication of Melanocortin receptor 1 (Mc1r) in the cavefish genome. This locus was discovered following the observation of excessive allelic diversity in a ∼820 bp fragment of Mc1r amplified via degenerate PCR from a natural population of Astyanax aeneus fish from Guerrero, Mexico. The cavefish genome reveals the presence of two closely related Mc1r open reading frames separated by a 1.46 kb intergenic region. One open reading frame corresponds to the previously reported Mc1r receptor, and the other open reading frame (duplicate copy) is 975 bp in length, encoding a receptor of 325 amino acids. Sequence similarity analyses position both copies in the syntenic region of the single Mc1r locus in 16 representative craniate genomes spanning bony fish (including Astyanax) to mammals, suggesting we discovered tandem duplicates of this important gene. The two Mc1r copies share ∼89% sequence similarity and, within Astyanax, are more similar to one another compared to other melanocortin family members. Future studies will inform the precise functional significance of the duplicated Mc1r locus and if this novel copy number variant may have adaptive significance for the Astyanax lineage.