Molecular analysis of the endosymbionts of tsetse flies: 16S rDNA locus and over-expression of a chaperonin.
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.
Aksoy
S
S
Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D018833:Chaperonins / Q000096:biosynthesis*; D004269:DNA, Bacterial / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006090:Gram-Negative Bacteria / Q000145:classification* / Q000235:genetics; D008969:Molecular Sequence Data; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D013559:Symbiosis; D014370:Tsetse Flies / Q000382:microbiology*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D018833:Chaperonins