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Comparative Genomics Reveals Thousands of Novel Chemosensory Genes and Massive Changes in Chemoreceptor Repertories across Chelicerates.

ABSTRACT: Chemoreception is a widespread biological function that is essential for the survival, reproduction, and social communication of animals. Though the molecular mechanisms underlying chemoreception are relatively well known in insects, they are poorly studied in the other major arthropod lineages. Current availability of a number of chelicerate genomes constitutes a great opportunity to better characterize gene families involved in this important function in a lineage that emerged and colonized land independently of insects. At the same time, that offers new opportunities and challenges for the study of this interesting animal branch in many translational research areas. Here, we have performed a comprehensive comparative genomics study that explicitly considers the high fragmentation of available draft genomes and that for the first time included complete genome data that cover most of the chelicerate diversity. Our exhaustive searches exposed thousands of previously uncharacterized chemosensory sequences, most of them encoding members of the gustatory and ionotropic receptor families. The phylogenetic and gene turnover analyses of these sequences indicated that the whole-genome duplication events proposed for this subphylum would not explain the differences in the number of chemoreceptors observed across species. A constant and prolonged gene birth and death process, altered by episodic bursts of gene duplication yielding lineage-specific expansions, has contributed significantly to the extant chemosensory diversity in this group of animals. This study also provides valuable insights into the origin and functional diversification of other relevant chemosensory gene families different from receptors, such as odorant-binding proteins and other related molecules.

SUBMITTER: Vizueta J

PROVIDER: S-EPMC5952958 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Comparative Genomics Reveals Thousands of Novel Chemosensory Genes and Massive Changes in Chemoreceptor Repertories across Chelicerates.

Vizueta Joel J Rozas Julio J Sánchez-Gracia Alejandro A

Genome biology and evolution 20180401 5

Chemoreception is a widespread biological function that is essential for the survival, reproduction, and social communication of animals. Though the molecular mechanisms underlying chemoreception are relatively well known in insects, they are poorly studied in the other major arthropod lineages. Current availability of a number of chelicerate genomes constitutes a great opportunity to better characterize gene families involved in this important function in a lineage that emerged and colonized la ...[more]

PMID: 29788250

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Project description:BACKGROUND:Geobacter species are delta-Proteobacteria and are often the predominant species in a variety of sedimentary environments where Fe(III) reduction is important. Their ability to remediate contaminated environments and produce electricity makes them attractive for further study. Cell motility, biofilm formation, and type IV pili all appear important for the growth of Geobacter in changing environments and for electricity production. Recent studies in other bacteria have demonstrated that signaling pathways homologous to the paradigm established for Escherichia coli chemotaxis can regulate type IV pili-dependent motility, the synthesis of flagella and type IV pili, the production of extracellular matrix material, and biofilm formation. The classification of these pathways by comparative genomics improves the ability to understand how Geobacter thrives in natural environments and better their use in microbial fuel cells. RESULTS:The genomes of G. sulfurreducens, G. metallireducens, and G. uraniireducens contain multiple (approximately 70) homologs of chemotaxis genes arranged in several major clusters (six, seven, and seven, respectively). Unlike the single gene cluster of E. coli, the Geobacter clusters are not all located near the flagellar genes. The probable functions of some Geobacter clusters are assignable by homology to known pathways; others appear to be unique to the Geobacter sp. and contain genes of unknown function. We identified large numbers of methyl-accepting chemotaxis protein (MCP) homologs that have diverse sensing domain architectures and generate a potential for sensing a great variety of environmental signals. We discuss mechanisms for class-specific segregation of the MCPs in the cell membrane, which serve to maintain pathway specificity and diminish crosstalk. Finally, the regulation of gene expression in Geobacter differs from E. coli. The sequences of predicted promoter elements suggest that the alternative sigma factors sigma28 and sigma54 play a role in regulating the Geobacter chemotaxis gene expression. CONCLUSION:The numerous chemoreceptors and chemotaxis-like gene clusters of Geobacter appear to be responsible for a diverse set of signaling functions in addition to chemotaxis, including gene regulation and biofilm formation, through functionally and spatially distinct signaling pathways.

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Dataset Information

Comparative Genomics Reveals Thousands of Novel Chemosensory Genes and Massive Changes in Chemoreceptor Repertories across Chelicerates.

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Comparative Genomics Reveals Thousands of Novel Chemosensory Genes and Massive Changes in Chemoreceptor Repertories across Chelicerates.

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