A highly divergent gene cluster in honey bees encodes a novel silk family

Genome Res. 2006 Nov;16(11):1414-21. doi: 10.1101/gr.5052606. Epub 2006 Oct 25.

Abstract

The pupal cocoon of the domesticated silk moth Bombyx mori is the best known and most extensively studied insect silk. It is not widely known that Apis mellifera larvae also produce silk. We have used a combination of genomic and proteomic techniques to identify four honey bee fiber genes (AmelFibroin1-4) and two silk-associated genes (AmelSA1 and 2). The four fiber genes are small, comprise a single exon each, and are clustered on a short genomic region where the open reading frames are GC-rich amid low GC intergenic regions. The genes encode similar proteins that are highly helical and predicted to form unusually tight coiled coils. Despite the similarity in size, structure, and composition of the encoded proteins, the genes have low primary sequence identity. We propose that the four fiber genes have arisen from gene duplication events but have subsequently diverged significantly. The silk-associated genes encode proteins likely to act as a glue (AmelSA1) and involved in silk processing (AmelSA2). Although the silks of honey bees and silkmoths both originate in larval labial glands, the silk proteins are completely different in their primary, secondary, and tertiary structures as well as the genomic arrangement of the genes encoding them. This implies independent evolutionary origins for these functionally related proteins.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Composition
  • Bees / genetics*
  • Bombyx / genetics
  • DNA / chemistry
  • DNA / genetics
  • Evolution, Molecular
  • Genes, Insect*
  • Genetic Variation
  • Insect Proteins / genetics*
  • Molecular Sequence Data
  • Multigene Family*
  • Sequence Homology, Amino Acid
  • Silk / genetics*
  • Species Specificity

Substances

  • Insect Proteins
  • Silk
  • DNA