Tag Archives: cerevisiae

Aspergillus comparative transcriptional profiling

ResearchBlogging.org

Researchers from Technical University of Denmark published some interesting results from comparing expression across the very distinct Aspergillus species.

Kudos also goes to making it Open Access. I am posting a few key figures below the fold because I can! They grew the fungi in bioreactors fermenting glucose or xylose. After calibrating the growth curves they were able to sample the appropriate time points for comparison of gene expression across these three species. They found a set of genes commonly expressed.

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New Saccharomyces resequencing assembly

SGRP LogoDavid Carter at the Sanger Centre emailed a message that new assemblies of Saccharomyces strain resequencing project have been posted including a new three-way alignment of S. bayanusS.paradoxusS.cerevisiae. This updates the Dec 2007 release.

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Neurospora speciation through experimental evolution

ResearchBlogging.orgDettman, Anderson, and Kohn recently published a paper in BMC Evolutionary Biology on reproductive experimental evolution in two Neurospora crassa populations evolved under different selective conditions. This is a great study that complements work published last year in Nature on experimental evolution in Saccharomyces cerevisiae populations. Neurospora populations were evolved under high salt and low temperature and were started from either high diversity (interspecific crosses, N. crassa vs N. intermedia) or low diversity (intraspecific cross, two N. crassa isolates D143 (Louisiana, USA)and D69 (Ivory Coast)) as described in Figure 1. The experimentally evolved populations were then tested for asexual and sexual fitness (they were taken through complete meiotic cycle throughout the experiment to avoid insure there was selection on the sexual reproduction pathway.

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More updates on Saccharomyces resequencing project at Sanger

I’ve paraphrased an email sent by David Carter to folks interested in Saccharomyces resequencing project.

The latest version of the SGRP data is on the web site and ftp site. This release is somewhat provisional, and motivated more by the fact that we have a paper deadline coming up than by any claim to finality. It should be quite a bit better than what was there before, but doesn’t have a correct treatment of transposons.

You can get the data by starting here:
http://www.sanger.ac.uk/Teams/Team71/durbin/sgrp/datadoc.shtml

There is also a new version of the browser:
http://www.sanger.ac.uk/Teams/Team71/durbin/sgrp/browser.shtml

There are a few new features in the browser which [David] is going to document over the next couple of days.

Major new features of the data are that there should be much better consistency between alignments; Solexa/Illumina data has been incorporated for the strains that had it; and the S. paradoxus alignments are based on a new assembly that created a few weeks ago and which covers about 95% of the genome; a description is at
http://www.sanger.ac.uk/Teams/Team71/durbin/sgrp/spara_assembly.shtml

Whole genome tiling arrays

A recent paper describes the discovery of 9 new introns in Saccharomyces cerevisiae by Ron Davis’s group at Stanford, using high density tiling arrays from Affymetrix. The arrays are designed for both strands allow the detection of transcripts transcribed from both strands. The arrays were also put to work by the Davis and Steinmetz labs to create a high density map of transcription in yeast and for polymorphism mapping from the Kruglyak lab.

PNAS Yeast Transcriptional map

Whole genome tiling arrays have also been employed in other fungi. For example, Anita Sil’s group at UCSF constructed a random tiling array for Histoplasma capsulatum and used it to identify genes responding to reactive nitrogen species. A similar approach was used in Cryptococcus neoformans to investigate temperature regulated genes using random sequencing clones.

As the technology has become cheaper, it may become sensible to use a tiling array to detect transcripts rather than ESTs when attempting to annotate a genome. In the Histoplasma work transcriptional units could be identified from hybridization alone. Some of the algorithms will need some work to correct incorporate this information, and the sensitivity and density of the array will influence this. These techniques can be part of a resequencing approaches or fast genotyping progeny from QTL experiments when the sequence from both parents is known (or at least enough of the polymorphims for the genetic map).

What is superior about the current Affymetrix yeast tiling array is the inclusion of both strands. This allows detection of transcripts from both strands. Several anti-sense transcripts in yeast have been discovered recently including in the IME4 locus through more classical approaches, but perhaps many more await discovery with high resolution transcriptional data from whole genome tiling arrays.