Dataset Information

Large scale and significant expression from pseudogenes in Sodalis glossinidius - a facultative endosymbiont C4PR_LIV

ABSTRACT: The majority of bacterial genomes have high coding efficiencies, but there are an few genomes of the intracellular bacteria that have low gene density. The genome of the endosymbiont Sodalis glossinidius contains almost 50% pseudogenes containing mutations that putatively silence them at the genomic level. We have applied multiple omic strategies: combining single molecule DNA-sequencing and annotation; stranded RNA-sequencing and proteome analysis to better understand the transcriptional and translational landscape of Sodalis pseudogenes, and potential mechanisms for their control. Between 53% and 74% of the Sodalis transcriptome remains active in cell-free culture. Mean sense transcription from Coding Domain Sequences (CDS) is four-times greater than that from pseudogenes. Core-genome analysis of six Illumina sequenced Sodalis isolates from different host Glossina species shows pseudogenes make up ~40% of the 2,729 genes in the core genome, suggesting are stable and/or Sodalis is a recent introduction across the Glossina genus as a facultative symbiont. These data further shed light on the importance of transcriptional and translational control in deciphering host-microbe interactions, and demonstrate that pseudogenes are more complex than a simple degrading DNA sequence. For this reason, we show that combining genomics, transcriptomics and proteomics represents an important resource for studying prokaryotic genomes with a view to elucidating evolutionary adaptation to novel environmental niches.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Sodalis Glossinidius

SUBMITTER: Philip Brownridge

LAB HEAD: Robert Beynon

PROVIDER: PXD007068 | Pride | 2020-05-26

REPOSITORIES: Pride

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Large-scale and significant expression from pseudogenes in <i>Sodalis glossinidius</i> - a facultative bacterial endosymbiont.

Goodhead Ian I Blow Frances F Brownridge Philip P Hughes Margaret M Kenny John J Krishna Ritesh R McLean Lynn L Pongchaikul Pisut P Beynon Rob R Darby Alistair C AC

Microbial genomics 20200101 1

The majority of bacterial genomes have high coding efficiencies, but there are some genomes of intracellular bacteria that have low gene density. The genome of the endosymbiont <i>Sodalis glossinidius</i> contains almost 50 % pseudogenes containing mutations that putatively silence them at the genomic level. We have applied multiple 'omic' strategies, combining Illumina and Pacific Biosciences Single-Molecule Real-Time DNA sequencing and annotation, stranded RNA sequencing and proteome analysis ...[more]

PMID: 31922467

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Project description:Approximately half of M. lepraeâ??s transcriptome consists of inactive gene products. This has an impact on overall energy and resource consumption without potential benefit to this organism. However, multiple translational â??silencingâ?? mechanisms are present, reducing additional energy and resource expenditure required for protein production from these transcripts. The Mycobacterium leprae genome has less than 50% coding capacity and 1,133 pseudogenes. Preliminary evidence suggests that some pseudogenes are expressed. Therefore, defining pseudogene transcriptional and translational potentials should increase our understanding of their impact on M. leprae physiology. To address this, M. leprae was purified from the granulomatous hind footpad tissue of four individual nu/nu nude mice six months post-infection. M. leprae whole genome DNA microarrays representing the 1,614 annotated ORFs and 1,133 identified pseudogenes, were obtained from the Leprosy Research Support and Maintenance of an Armadillo Colony Post-Genome Era, Part I: Leprosy Research Support Contract (NO1 AI-25469) at Colorado State University. To validate 20% of genes positive by microarray analysis, RT-PCR was performed. Results of this study Gene expression analysis identified transcripts from 49% of all M. leprae genes including 57% of all ORFs and 43% of all pseudogenes in the genome. Pseudogenes were randomly distributed throughout the chromosome. Factors resulting in pseudogene transcription included: 1) co-orientation of transcribed pseudogenes with transcribed ORFs within or exclusive of operon-like structures; 2) the paucity of intrinsic stem-loop transcriptional terminators between transcribed ORFs and downstream pseudogenes; and 3) predicted pseudogene promoters. Mechanisms for translational silencing of pseudogene transcripts included the lack of both translational start codons and strong Shine-Dalgarno sequences. Transcribed pseudogenes also contained multiple in-frame stop codons and high Ka/Ks ratios, compared to that of homologs in M. tuberculosis and ORFs in M. leprae. A pseudogene transcript containing an active promoter, strong SD site, a start codon, but containing two in frame stop codons yielded a protein product when expressed in E. coli. Approximately half of M. leprae's transcriptome consists of inactive gene products consuming energy and resources without potential benefit to M. leprae. Presently it is unclear what additional detrimental affect(s) this large number of inactive mRNAs has on the functional capability of this organism. Translation of these pseudogenes may play an important role in overall energy consumption and resultant pathophysiological characteristics of M. leprae. However, this study also demonstrated that multiple translational silencing mechanisms are present, reducing additional energy and resource expenditure required for protein production from the vast majority of these transcripts. The overall design of this study was to identify the transcriptome of M. leprae in the granulomatous tissue of the mouse hind foot pad 6 months post infection.

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