Dataset Information

The determinants of gene order conservation in yeasts.

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.

SUBMITTER: Poyatos JF

PROVIDER: S-EPMC2258174 | biostudies-literature | 2007

REPOSITORIES: biostudies-literature

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Publications

The determinants of gene order conservation in yeasts.

Poyatos Juan F JF Hurst Laurence D LD

Genome biology 20070101 11

<h4>Background</h4>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.<h4>Results</h4>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 ...[more]

PMID: 17983469

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Project description:The order of genes in eukaryotes is not entirely random. Studies of gene order conservation are important to understand genome evolution and to reveal mechanisms why certain neighboring genes are more difficult to separate during evolution. Here, genome-wide gene order information was compiled for 64 species, representing a wide variety of eukaryotic phyla. This information is presented in a browser where gene order may be displayed and compared between species. Factors related to non-random gene order in eukaryotes were examined by considering pairs of neighboring genes. The evolutionary conservation of gene pairs was studied with respect to relative transcriptional direction, intergenic distance and functional relationship as inferred by gene ontology. The results show that among gene pairs that are conserved the divergently and co-directionally transcribed genes are much more common than those that are convergently transcribed. Furthermore, highly conserved pairs, in particular those of fungi, are characterized by a short intergenic distance. Finally, gene pairs of metazoa and fungi that are evolutionary conserved and that are divergently transcribed are much more likely to be related by function as compared to poorly conserved gene pairs. One example is the ribosomal protein gene pair L13/S16, which is unusual as it occurs both in fungi and alveolates. A specific functional relationship between these two proteins is also suggested by the fact that they are part of the same operon in both eubacteria and archaea. In conclusion, factors associated with non-random gene order in eukaryotes include relative gene orientation, intergenic distance and functional relationships. It seems likely that certain pairs of genes are conserved because the genes involved have a transcriptional and/or functional relationship. The results also indicate that studies of gene order conservation aid in identifying genes that are related in terms of transcriptional control.

Project description:'Ca. Liberibacter asiaticus,' an insect-vectored, obligate intracellular bacterium associated with citrus-greening disease, also called "HLB," is a member of the Rhizobiales along with nitrogen-fixing microsymbionts Sinorhizobium meliloti and Bradyrhizobium japonicum, plant pathogen Agrobacterium tumefaciens and facultative intracellular mammalian pathogen Bartonella henselae. Comparative analyses of their circular chromosomes identified 514 orthologous genes shared among all five species. Shared among all five species are 50 identical blocks of microsyntenous orthologous genes (MOGs), containing a total of 283 genes. While retaining highly conserved genomic blocks of microsynteny, divergent evolution, horizontal gene transfer and niche specialization have disrupted macrosynteny among the five circular chromosomes compared. Highly conserved microsyntenous gene clusters help define the Rhizobiales, an order previously defined by 16S RNA gene similarity and herein represented by the three families: Bartonellaceae, Bradyrhizobiaceae and Rhizobiaceae. Genes without orthologs in the other four species help define individual species. The circular chromosomes of each of the five Rhizobiales species examined had genes lacking orthologs in the other four species. For example, 63 proteins are encoded by genes of 'Ca. Liberibacter asiaticus' not shared with other members of the Rhizobiales. Of these 63 proteins, 17 have predicted functions related to DNA replication or RNA transcription, and some of these may have roles related to low genomic GC content. An additional 17 proteins have predicted functions relevant to cellular processes, particularly modifications of the cell surface. Seventeen unshared proteins have specific metabolic functions including a pathway to synthesize cholesterol encoded by a seven-gene operon. The remaining 12 proteins encoded by 'Ca. Liberibacter asiaticus' genes not shared with other Rhizobiales are of bacteriophage origin. 'Ca. Liberibacter asiaticus' shares 11 genes with only Sinorhizobium meliloti and 12 genes are shared with only Bartonella henselae.

Dataset Information

The determinants of gene order conservation in yeasts.

Background

Results

Conclusion

Publications

The determinants of gene order conservation in yeasts.

Similar Datasets

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