Biology subjects

Whelan, F. J.

Publications and source records attributed to Whelan, F. J..

3 recordsLinked to original sources

bioRxiv2021

Gene-gene relationships in an Escherichia coli accessory genome are linked to function and mobility

The pangenome contains all genes encoded by a species, with the core genome present in all strains and the accessory genome in only a subset. Coincident gene relationships are expected within the accessory genome, where the presence or absence of one gene is influenced by the presence or absence of another. Here, we analysed the accessory genome of an Escherichia coli pangenome consisting of 400 genomes from 20 sequence types to identify genes that display significant co-occurrence or avoidance patterns with one another. We present a complex network of genes that are either found together or that avoid one another more often than would be expected by chance, and show that these relationships vary by lineage. We demonstrate that genes co-occur by function, and that several highly connected gene relationships are linked to mobile genetic elements. We find that genes are more likely to co-occur with, rather than avoid, another gene, suggesting that cooperation is more common than conflict in the accessory genome. This work furthers our understanding of the dynamic nature of prokaryote pangenomes and implicates both function and mobility as drivers of gene relationships. Data summaryAll Supplementary Data files and the Python scripts used in the analyses are available at doi.org/10.17639/nott.7103. Impact statementThe pangenome of a species encompasses the core genes encoded by all genomes, as well as the accessory genes found in only a subset. Much remains to be understood about the relationships and interactions between accessory genes; in particular, what drives pairs of genes to appear together in the same genome, or what prevents them from being in the same genome together, more often than expected by chance. How these co-occurrence and avoidance relationships develop, and what effect they have on the dynamics and evolution of the pangenome as a whole, is largely unknown. Here, we present a springboard for understanding prokaryote pangenome evolution by uncovering significant gene relationships in a model Escherichia coli pangenome. We identify mobile genetic elements and the sharing of common function as possible driving forces behind the co-occurrence of accessory genes. Furthermore, this work offers an extensive dataset from which gene relationships could be identified for any gene of interest in this E. coli accessory genome, providing a rich resource for the community.

evolutionary biology↗

bioRxiv2020

Evidence for selection in a prokaryote pangenome

A pangenome is the complete set of genes (core and accessory) present in a phylogenetic clade. We hypothesize that a pangenomes accessory gene content is structured and maintained by selection. To test this hypothesis, we interrogated the genomes of 40 Pseudomonas genomes for statistically significant coincident (i.e. co-occurring/avoiding) gene patterns. We found that 86.7% of common accessory genes are involved in [≥]1 coincident relationship. Further, genes that co-occur and/or avoid each other - but are not vertically or horizontally co-inherited - are more likely to share Gene Ontology categories, are more likely to be simultaneously transcribed, and are more likely to produce interacting proteins, than would be expected by chance. These results are not due to coincident genes being adjacent to one another on the chromosome. Together, these findings suggest that the accessory genome is structured into interacting sets of genes co-selected to function together within a given strain. Given the simi larity of the Pseudomonas pangenome with open pangenomes of other prokaryotic species, we speculate that these results are generalizable.

microbiology↗

bioRxiv2019

Coinfinder: Detecting Significant Associations and Dissociations in Pangenomes

2.The accessory genes of prokaryote and eukaryote pangenomes accumulate by horizontal gene transfer, differential gene loss, and the effects of selection and drift. We have developed Coinfinder, a software program that assesses whether sets of homologous genes (gene families) in pangenomes associate or dissociate with each other (i.e. are "coincident") more often than would be expected by chance. Coinfinder employs a user-supplied phylogenetic tree in order to assess the lineage-dependence (i.e. the phylogenetic distribution) of each accessory gene, allowing Coinfinder to focus on coincident gene pairs whose joint presence is not simply because they happened to appear in the same clade, but rather that they tend to appear together more often than expected across the phylogeny. Coinfinder is implemented in C++, Python3, and R and is freely available under the GPU license from https://github.com/fwhelan/coinfinder. 3. Impact statementCoinfinder identifies genes that co-occur (associate) or avoid (dissociate) with each other across the accessory genomes of a pangenome of interest. Genes that associate or dissociate more often than expected by chance, suggests that those genes have a connection (attraction or repulsion) that is interesting to explore. Identification of these groups of genes will further the fields understanding of the importance of accessory genes. Coinfinder is a freely available, open-source software which can identify gene patterns locally on a personal computer in a matter of hours. 4. Data summaryO_LICoinfinder is freely available at https://github.com/fwhelan/coinfinder. C_LIO_LIA list of the Identifiers of the genomes used within as well as all input/output files are available at https://github.com/fwhelan/coinfinder-manuscript. C_LI The authors confirm all supporting data, code and protocols have been provided within the article or through supplementary data files.

microbiology↗