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The determinants of gene order conservation in yeasts

Juan F Poyatos1* and Laurence D Hurst2

Author Affiliations

1 Logic of Genomic Systems Laboratory, Spanish National Biotechnology Centre, Centro Superior de Investigaciones Científicas (CSIC), Darwin 3, Campus de Cantoblanco, Madrid 28049, Spain

2 Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK

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Genome Biology 2007, 8:R233  doi:10.1186/gb-2007-8-11-r233

Published: 5 November 2007

Abstract

Background

Why do some groups of physically linked genes stay linked over long evolutionary periods? Although several factors are associated with the formation of gene clusters in eukaryotic genomes, the particular contribution of each feature to clustering maintenance remains unclear.

Results

We quantify the strength of the proposed factors in a yeast lineage. First we identify the magnitude of each variable to determine linkage conservation by using several comparator species at different distances to Saccharomyces cerevisiae. For adjacent gene pairs, in line with null simulations, intergenic distance acts as the strongest covariate. Which of the other covariates appear important depends on the comparator, although high co-expression is related to synteny conservation commonly, especially in the more distant comparisons, these being expected to reveal strong but relatively rare selection. We also analyze those pairs that are immediate neighbors through all the lineages considered. Current intergene distance is again the best predictor, followed by the local density of essential genes and co-regulation, with co-expression and recombination rate being the weakest predictors. The genome duplication seen in yeast leaves some mark on linkage conservation, as adjacent pairs resolved as single copy in all post-whole genome duplication species are more often found as adjacent in pre-duplication species.

Conclusion

Current intergene distance is consistently the strongest predictor of synteny conservation as expected under a simple null model. Other variables are of lesser importance and their relevance depends both on the species comparison in question and the fate of the duplicates following genome duplication.