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Comparative transcriptomics across the prokaryotic tree of life.

ABSTRACT: Whole-transcriptome sequencing studies from recent years revealed an unexpected complexity in transcriptomes of bacteria and archaea, including abundant non-coding RNAs, cis-antisense transcription and regulatory untranslated regions (UTRs). Understanding the functional relevance of the plethora of non-coding RNAs in a given organism is challenging, especially since some of these RNAs were attributed to 'transcriptional noise'. To allow the search for conserved transcriptomic elements we produced comparative transcriptome maps for multiple species across the microbial tree of life. These transcriptome maps are detailed in annotations, comparable by gene families, and BLAST-searchable by user provided sequences. Our transcriptome collection includes 18 model organisms spanning 10 phyla/subphyla of bacteria and archaea that were sequenced using standardized RNA-seq methods. The utility of the comparative approach, as implemented in our web server, is demonstrated by highlighting genes with exceptionally long 5'UTRs across species, which correspond to many known riboswitches and further suggest novel putative regulatory elements. Our study provides a standardized reference transcriptome to major clinically and environmentally important microbial phyla. The viewer is available at http://exploration.weizmann.ac.il/TCOL, setting a framework for comparative studies of the microbial non-coding genome.

SUBMITTER: Cohen O

PROVIDER: S-EPMC4987935 | biostudies-literature | 2016 Jul

REPOSITORIES: biostudies-literature

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Comparative transcriptomics across the prokaryotic tree of life.

Cohen Ofir O Doron Shany S Wurtzel Omri O Dar Daniel D Edelheit Sarit S Karunker Iris I Mick Eran E Sorek Rotem R

Nucleic acids research 20160506 W1

Whole-transcriptome sequencing studies from recent years revealed an unexpected complexity in transcriptomes of bacteria and archaea, including abundant non-coding RNAs, cis-antisense transcription and regulatory untranslated regions (UTRs). Understanding the functional relevance of the plethora of non-coding RNAs in a given organism is challenging, especially since some of these RNAs were attributed to 'transcriptional noise'. To allow the search for conserved transcriptomic elements we produce ...[more]

PMID: 27154273

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Project description:Microorganisms dominate all ecosystems on Earth and play a key role in the turnover of organic matter. By producing enzymes, they degrade complex carbohydrates, facilitating the recycling of nutrients and controlling the carbon cycle. Despite their importance, our knowledge regarding microbial carbohydrate utilization has been limited to genome-sequenced taxa and thus heavily biased to specific groups and environments. Here, we used the Genomes from Earth's Microbiomes (GEM) catalog to describe the carbohydrate utilization potential in >7000 bacterial and archaeal taxa originating from a range of terrestrial, marine and host-associated habitats. We show that the production of carbohydrate-active enzymes (CAZymes) is phylogenetically conserved and varies significantly among microbial phyla. High numbers of carbohydrate-active enzymes were recorded in phyla known for their versatile use of carbohydrates, such as Firmicutes, Fibrobacterota, and Armatimonadota, but also phyla without cultured representatives whose carbohydrate utilization potential was so far unknown, such as KSB1, Hydrogenedentota, Sumerlaeota, and UBP3. Carbohydrate utilization potential reflected the specificity of various habitats: the richest complements of CAZymes were observed in MAGs of plant microbiomes, indicating the structural complexity of plant biopolymers. IMPORTANCE This study expanded our knowledge of the phylogenetic distribution of carbohydrate-active enzymes across prokaryotic tree of life, including new phyla where the carbohydrate-active enzymes composition have not been described until now and demonstrated the potential for carbohydrate utilization of numerous yet uncultured phyla. Profiles of carbohydrate-active enzymes are largely habitat-specific and reflect local carbohydrate availability by selecting taxa with appropriate complements of these enzymes. This information should aid in the prediction of functions in microbiomes of known taxonomic composition and helps to identify key components of habitat-specific carbohydrate pools. In addition, these findings have a high relevance for the understanding of carbohydrate utilization and carbon cycling in the environment, the process that is closely link to the carbon storage potential of Earth habitats and the production of greenhouse gasses.

Project description:BACKGROUND: Barley and particularly wheat are two grass species of immense agricultural importance. In spite of polyploidization events within the latter, studies have shown that genotypically and phenotypically these species are very closely related and, indeed, fertile hybrids can be created by interbreeding. The advent of two genome-scale Affymetrix GeneChips now allows studies of the comparison of their transcriptomes. RESULTS: We have used the Wheat GeneChip to create a "gene expression atlas" for the wheat transcriptome (cv. Chinese Spring). For this, we chose mRNA from a range of tissues and developmental stages closely mirroring a comparable study carried out for barley (cv. Morex) using the Barley1 GeneChip. This, together with large-scale clustering of the probesets from the two GeneChips into "homologous groups", has allowed us to perform a genomic-scale comparative study of expression patterns in these two species. We explore the influence of the polyploidy of wheat on the results obtained with the Wheat GeneChip and quantify the correlation between conservation in gene sequence and gene expression in wheat and barley. In addition, we show how the conservation of expression patterns can be used to elucidate, probeset by probeset, the reliability of the Wheat GeneChip. CONCLUSION: While there are many differences in expression on the level of individual genes and tissues, we demonstrate that the wheat and barley transcriptomes appear highly correlated. This finding is significant not only because given small evolutionary distance between the two species it is widely expected, but also because it demonstrates that it is possible to use the two GeneChips for comparative studies. This is the case even though their probeset composition reflects rather different design principles as well as, of course, the present incomplete knowledge of the gene content of the two species. We also show that, in general, the Wheat GeneChip is not able to distinguish contributions from individual homoeologs. Furthermore, the comparison between the two species leads us to conclude that the conservation of both gene sequence as well as gene expression is positively correlated with absolute expression levels, presumably reflecting increased selection pressure on genes coding for proteins present at high levels. In addition, the results indicate the presence of a correlation between sequence and expression conservation within the Triticeae.

Dataset Information

Comparative transcriptomics across the prokaryotic tree of life.

Publications

Comparative transcriptomics across the prokaryotic tree of life.

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