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. 2002 Jun;12(6):962-8.
doi: 10.1101/gr.87702.

Essential genes are more evolutionarily conserved than are nonessential genes in bacteria

I King Jordan  1 , Igor B Rogozin, Yuri I Wolf, Eugene V Koonin
Affiliations

Essential genes are more evolutionarily conserved than are nonessential genes in bacteria

I King Jordan et al. Genome Res. 2002 Jun.

Abstract

The "knockout-rate" prediction holds that essential genes should be more evolutionarily conserved than are nonessential genes. This is because negative (purifying) selection acting on essential genes is expected to be more stringent than that for nonessential genes, which are more functionally dispensable and/or redundant. However, a recent survey of evolutionary distances between Saccharomyces cerevisiae and Caenorhabditis elegans proteins did not reveal any difference between the rates of evolution for essential and nonessential genes. An analysis of mouse and rat orthologous genes also found that essential and nonessential genes evolved at similar rates when genes thought to evolve under directional selection were excluded from the analysis. In the present study, we combine genomic sequence data with experimental knockout data to compare the rates of evolution and the levels of selection for essential versus nonessential bacterial genes. In contrast to the results obtained for eukaryotic genes, essential bacterial genes appear to be more conserved than are nonessential genes over both relatively short (microevolutionary) and longer (macroevolutionary) time scales.

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Figures

Figure 1
Figure 1
Bootstrap test of the average rates of synonymous (Ks), nonsynonymoys (Ka), and Ka/Ks for essential and nonessential Escherichia coli genes. Frequency distributions for the average values of Ka, Ks, and Ka/Ks for 1000 bootstrap replicates are shown.
Figure 2
Figure 2
Average phyletic distribution parameter values for essential (E) and nonessential (NE) genes in the three bacterial species surveyed. Average values (±SE) are shown above the bars. For the definition of the phyletic distribution parameter (PDP), see Methods.
See this image and copyright information in PMC

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