Tag Archives: sequence

Dermatophyte genome sequences

The first of several dermatophyte fungal genomes, Microsporum gypseum, has been released at the Broad’s Dermatophyte site.  Two Tricophyton species and another Microsporum genome should follow soon. These dermatophyte fungi are Onygenales (Ascomycota) fungi (like Coccidioides and Histoplasma), although their placement in the phylogenies shown in the whitepaper and related review paper is a bit ambiguous. I’m sure that can be improved with a few more gene sequences gleaned from the genomes.

The 23 Mb M. gypseum genome is a bit smaller than the sizes of C. immitis (28 Mb), H. capsulatum (32 Mb), or Paracoccidioides brasiliensis (29 Mb).  While no annotation is currently available for the M. gypseum genome, this genome will help in establishing what genes were ancestral in the Onygenales and comparing patterns of gene family gains and losses in fungi that specialize on animal hosts.

Some more comparison across different kinds of dermatophyte fungi that are very distantly related like dandruff causing fungus Malasezzia globosa (Basidiomycota) will be really interesting as well.

Thanks Joe H and FGI folks for passing along announcement and to the Broad/FGI folks for the work to make this sequence available.

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.