Operon Formation is Driven by Co-Regulation and Not by Horizontal Gene Transfer
Although operons are often subject to horizontal gene transfer (HGT), non-HGT genes are particularly likely to be in operons. To resolve this apparent discrepancy and to determine whether HGT is involved in operon formation, we examined the evolutionary history of the genes and operons in Escherichia coli K12. We show that genes that have homologs in distantly related bacteria but not in close relatives of E. coli (indicating HGTi) form new operons at about the same rates as native genes. Furthermore, genes in new operons are no more likely than other genes to have phylogenetic trees that are inconsistent with the species tree. In contrast, essential genes and ubiquitous genes without paralogs (genes believed to undergo HGT rarely) often form new operons. We conclude that HGT is not associated with operon formation, but instead promotes the prevalence of pre-existing operons. To explain operon formation, we propose that new operons reduce the amount of regulatory information required to specify optimal expression patterns. Consistent with this hypothesis, operons have greater amounts of conserved regulatory sequences than do individually transcribed genes.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director. Office of Science. Office of Biological and Environmental Research, Genomics to Life Program; Howard Hughes Medical Institute
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 843009
- Report Number(s):
- LBNL-57448; R&D Project: VGTLAA; TRN: US200516%%1232
- Resource Relation:
- Other Information: Journal Publication Date: 06/2005
- Country of Publication:
- United States
- Language:
- English
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