Molecular analysis of the endosymbionts of tsetse flies: 16S rDNA locus and over-expression of a chaperonin

Insect Mol Biol. 1995 Feb;4(1):23-9. doi: 10.1111/j.1365-2583.1995.tb00004.x.


Based on 16S rDNA sequence comparison, intracellular mycetome-associated endosymbionts (P-endosymbionts) of tsetse flies (Diptera: Glossinidae) form a distinct lineage within the gamma-3 subdivision of proteobacteria, related to the free-living bacterium Escherichia coli, midgut S-endosymbionts of various insects including tsetse flies, and to the P-endosymbiont lineage of aphids, Buchnera aphidicola. Gene organization and expression of several loci in intracellular microorganisms have revealed differences from free-living bacteria. This study analyses two of these characteristics in tsetse endosymbionts; the copy number and gene organization of rDNA operations and the nature of the abundant protein(s) synthesized by these microorganisms. Results indicate that Glossina morsitans morsitans S-endosymbionts have multiple (seven) rDNA operons coding for 16S (rrs) followed by 23S (rrl) gene sequences, whereas tsetse P-endosymbionts have a single, similarly organized rDNA operon. In tsetse mycetocytes in vitro, P-endosymbionts synthesize a predominant protein of 60 kDa in size (p60) which by Western blot analysis shows immunological cross-reactivity with the abundant 63 kDa (p63) protein of B. aphidicola. p63 (also referred to as symbionin) has been characterized as a molecular chaperone, structurally and functionally similar to the groEL protein of E. coli. Under in vitro conditions, tsetse S-endosymbionts synthesize high levels of a similarly-sized protein that cross-reacts with p63 chaperonin. Antisera against the tsetse p60 protein also recognizes p63 protein of B. aphidicola, suggesting that the abundant tsetse endosymbiont protein is a chaperonin.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bacterial Proteins / metabolism
  • Base Sequence
  • Chaperonins / biosynthesis*
  • DNA, Bacterial / genetics*
  • Gene Expression Regulation, Bacterial
  • Genes, Bacterial
  • Gram-Negative Bacteria / classification*
  • Gram-Negative Bacteria / genetics
  • Molecular Sequence Data
  • RNA, Bacterial / genetics
  • RNA, Ribosomal, 16S / genetics*
  • Symbiosis*
  • Tsetse Flies / microbiology*


  • Bacterial Proteins
  • DNA, Bacterial
  • RNA, Bacterial
  • RNA, Ribosomal, 16S
  • Chaperonins