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Organization and structure of tRNA genes in Spiroplasma melliferum
M J Rogers1, A A Steinmetz, R T Walker
1Institut de Biologie Moleculaire et Cellulaire du CNRS, Strasbourg, France.
Abstract:
To investigate the organization of tRNA genes in the honeybee pathogen, Spiroplasma melliferum (previously referred to as Spiroplasma sp. BC3), total labeled tRNA from S. melliferum was used as a hybridization probe to an EcoRI digest of the genomic DNA. The results show two, or possibly three, strongly hybridizing bands. Comparing the pattern obtained to that of Bacillus subtilis DNA suggests either that the S. melliferum tRNA genes are more extensively clustered or, more likely, that the S. melliferum genome does not encode a full complement of tRNA genes, as has been suggested for other Mollicutes. We screened a library of EcoRI fragments of S. melliferum DNA cloned in pBR322 with total radioactive tRNA as a probe and selected one of the tRNA gene clusters. Subsequent sequence analysis of a portion of the clone showed 10 tRNA genes probably comprising a single operon. Comparison of sequence with a tRNA gene cluster from Mycoplasma mycoides and a portion of a cluster from B. subtilis showed an identical order of tRNA genes and the isoacceptors encoded. Such a striking comparison in gram-positive eubacteria suggests an important function for regulation and co-transcription of these tRNA genes.
Insights
Spiroplasma melliferum tRNA gene organization was investigated, revealing clustered genes potentially indicating an incomplete set. This organization mirrors that in other gram-positive bacteria, suggesting conserved co-transcription functions.
Area of Science:
- Microbiology
- Genomics
- Molecular Biology
Background:
- Spiroplasma melliferum is a honeybee pathogen.
- The organization of transfer RNA (tRNA) genes in Spiroplasma species is not well understood.
- Previous studies suggest Mollicutes may not encode a full complement of tRNA genes.
Purpose of the Study:
- To investigate the organization and structure of tRNA genes in Spiroplasma melliferum.
- To compare the tRNA gene organization with other bacterial species.
Main Methods:
- Hybridization of labeled S. melliferum tRNA to EcoRI-digested genomic DNA.
- Screening of an S. melliferum DNA library cloned in pBR322 using tRNA as a probe.
- Sequence analysis of selected tRNA gene clusters.
Main Results:
- Hybridization revealed two or three strongly hybridizing bands, suggesting clustered tRNA genes.
- Sequence analysis identified a cluster of 10 tRNA genes, likely forming a single operon.
- The order of tRNA genes and encoded isoacceptors was identical to that found in Mycoplasma mycoides and Bacillus subtilis.
Conclusions:
- S. melliferum tRNA genes are extensively clustered, possibly indicating an incomplete tRNA gene set.
- The conserved organization of tRNA genes suggests functional importance for regulation and co-transcription in gram-positive eubacteria.