Abstract
Bumble bees exhibit exceptional diversity in their segmental body coloration largely as a result of mimicry. In this study we sought to discover genes involved in this variation through studying a lab-generated mutant in bumble bee Bombus terrestris, in which the typical black coloration of the pleuron, scutellum, and first metasomal tergite is replaced by yellow, a color variant also found in sister lineages to B. terrestris. Utilizing a combination of RAD-Seq and whole-genome re-sequencing, we localized the color-generating variant to a single SNP in the protein-coding sequence of transcription factor cut. This mutation generates an amino acid change that modifies the conformation of a coiled-coil structure outside DNA-binding domains. We found that all sequenced Hymenoptera, including sister lineages, possess the non-mutant allele, indicating different mechanisms are involved in the same color transition in nature. Cut is important for multiple facets of development, yet this mutation generated no noticeable external phenotypic effects outside of setal characteristics. Reproductive capacity was reduced, however, as queens were less likely to mate and produce female offspring, exhibiting behavior similar to that of workers. Our research implicates a novel developmental player in pigmentation, and potentially caste, thus contributing to a better understanding of the evolution of diversity in both of these processes.
Highlights
Understanding the genetic architecture underlying phenotypic diversification has been a long-standing goal of evolutionary biology
In our current research study, we aim to unravel the genomic basis of mutant yellow coloration in B. terrestris
Utilizing a combination of reduced-representation and whole-genome sequencing, we identified the color-controlling locus in the yellow mutant phenotype in B. terrestris to a single non-synonymous SNP in a homeobox transcription factor, cut
Summary
Understanding the genetic architecture underlying phenotypic diversification has been a long-standing goal of evolutionary biology. Discoveries and understanding of the genetic basis of traits relied on fortuitous mutant phenotypes predominantly in Drosophila[1,2] and subsequently in other model organisms (reviewed in Ref.[3]) These studies have contributed myriad insights about the characteristics, chromosomal arrangement, and functional interactions of involved genes but have shed light on the complex genomic mechanisms involved in natural variation[4]. This fortuitous mutant enables assessment of the genetic basis of this trait using laboratory crosses
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