Tag Archives: genome sequencing

Microsporidia genomes on the way

New genomes from Microsporidia are on the way from the Broad Institute and other groups, and will be a boon to those working on these fascinating creatures. Microsporidia are obligate intracellular parasites of eukaryotic cells and many can cause serious disease in humans. Some parasitize worms and insects too. The evolutionary placement of these species in the fungi is still debated with recent evidence placing them as derived members of the Mucormycotina based on shared synteny (conserved gene order), in particular around the mating type locus.  There is still some debate as to where this group belongs in the Fungal kingdom, with their highly derived characteristics and long branches they are still make them hard to place.  The synteny-based evidence was another way to find a phylogenetic placement for them but it would be helpful to have additional support in the form of additional shared derived characteristics that group Mucormycotina and Microsporidia. There is hope that increased number of genome sequences and phylogenomic approaches can help resolve the placement and more further understand the evolution of the group.

For data analysis, a new genome database for comparing these genomes is online called MicrosporidiaDB. This project has begun incorporating the available genomes and providing a data mining interface that extends from the EuPathDB project.

I’ll have the truffles and huitlacoche

Black TruffleA couple of papers should have captured your attention lately in the realm of fungal genomics.

One is the publication of the genome of the black truffle Tuber melanosporum. This appears as an advanced publication at Nature (OA by virtue of Nature’s agreement on genome papers) along with a NYT writeup and is a tasty exploration of the genome of an ascomycete ectomycorrhizal (ECM) fungus. There are several gems in there including the differences in transposable element content, content of gene families related to carbohydrate metabolism. This genome helps open the doorway for exploring the several independent origins of ECM in both ascomycete and basidiomycete fungi.

I’ll also point out there is some work on the analysis of mating type locus found in this genome has applied aspects suggesting that inoculation of roots with both mating types may increase truffle yields in truffle farms. Evidence for sexual reproduction is also discovered from this genome analysis based on the sexual cycle genes present and the structure of the MAT locus.  Much like what was revealed in the genome analysis of the previously ‘asexual’ species Aspergillus fumigatus (and later reconstitution of a sexual cycle), the Tuber genome has the potential for mating and is a heterothallic (outcrossing) fungus based on its mating type locus -just like many other filamentous Ascomycete species.

A second paper I encourage you take a look at (those with a Science subscription) is from Virginia Walbot’s lab on the formation of tumors by U. maydis in Maize. These tumors end up destroying the corn but can produce a delicious (to some) dish that is huitlacooche. The idea that the fungus is co-opting the host system by secreting proteins that acted in the same way as native proteins and that it has a tissue or organ specific repertoire was one that her lab has been pursuing. U. maydis can grow inside corn without detection and  the formation of tumors seems to be a manipulation of the plant as much as it is the pathogen directly taking resources from the plant.  It reminds me a bit of the production of secondary metabolites that can control plant growth like gibberellins produced by fungi.  This kind of manipulation and also ability to evade detection suggests a pretty specific set of controls that prevent the fungus from doing the wrong thing at the wrong time (to avoid detection). So they set out to see if there are a set of organ specific genes that the fungus uses during infection that would suggest a very host-specific strategy by this corn smut.

In this paper the authors evaluate the role of fungal genes specifically expressed in infection of different organs and also the role of secreted proteins in colonization of the organs.  In what is impressive and elegant work, the authors show through the use of microarrays and genetics that there is plant tissue specific gene expression of U. maydis – so infections in leaves express a different set of genes than those in seedlings.  Genetic and phenotypic evaluation of fungal strains with knockouts of sets of the predicted secreted proteins was able to confirm a role for specific secreted proteins that previously may have not had any discernible phenotype. They infect strains with knockouts of sets of genes that encode secreted proteins and compare the virulence when these strains infect individual organs of the maize host.  They showed there is significantly different virulence in the various tissues for a some of the mutants suggesting an organ-specific role for virulence of secreted proteins. They also go on to show that some of this organ specific infection requires organ-specific gene expression by evaluating maize mutants and the ability of the fungus to infect different organs.

Future work will hopefully followup to see what these secreted proteins are manipulating in the host and how they either enable virulence by protecting the pathogen, avoiding detection by turning of host responses, or co-opting host gene networks in some other way.

Martin F, Kohler A, Murat C, Balestrini R, Coutinho PM, Jaillon O, Montanini B, Morin E, Noel B, Percudani R, Porcel B, Rubini A, Amicucci A, Amselem J, Anthouard V, Arcioni S, Artiguenave F, Aury JM, Ballario P, Bolchi A, Brenna A, Brun A, Buée M, Cantarel B, Chevalier G, Couloux A, Da Silva C, Denoeud F, Duplessis S, Ghignone S, Hilselberger B, Iotti M, Marçais B, Mello A, Miranda M, Pacioni G, Quesneville H, Riccioni C, Ruotolo R, Splivallo R, Stocchi V, Tisserant E, Viscomi AR, Zambonelli A, Zampieri E, Henrissat B, Lebrun MH, Paolocci F, Bonfante P, Ottonello S, & Wincker P (2010). Périgord black truffle genome uncovers evolutionary origins and mechanisms of symbiosis. Nature PMID: 20348908

Skibbe DS, Doehlemann G, Fernandes J, & Walbot V (2010). Maize tumors caused by Ustilago maydis require organ-specific genes in host and pathogen. Science (New York, N.Y.), 328 (5974), 89-92 PMID: 20360107

Sequencing wine spoilage yeast

There is an article in Wine Spectator (Seen on the JGI feed) on sequencing the wine spoilage yeast bruxellensis (correct name is now Dekkera bruxellensis) which adds the not-so-excellent taste of “sweaty horse” to wines.  There is already some survey sequencing done by Ken Wolfe and Jurge Piskur’s groups so a full genome sequencing project will help work out how this yeast is able to out compete Saccharomyces and cause dramatic wine spoilage.  This is also relevant on the bio-fuel side since this yeast can also taint an ethanol bio-reactor.  It is an interesting ecology inside the wine bottle and this competition for resources can lead to bad tasting wine. The competition presumably originated in some form in the rotting fruit where these yeasts compete for space and use different approaches in their niche including the fermentation process which produces the revered ethanol by-product and helps establish a chemical-warfare driven landgrab.  The ethanol also helps prevent and of course this has implications for the Drosophila (Sophophora) flies that land there and eat yeast. They needed a good way to overcome the ethanol like the well studied Adh gene.

Schizophyllum genome portal live at JGI

In preparation for Asilomar, JGI is releasing lots of the genome sequencing project portals. The Schizophyllum commune Genome Portal is now publicly available. Go get your white-rot gene investigation on! (Though please respect the community rules for 1st rights to publication of the genome-wide analyses).

Lichen genome projects and the power shift prompted by next-gen sequencing

Genome Technology highlights the very cool thing about next-gen sequencing – it puts the power in the hands of the researchers to explore genome sequence and doesn’t limit them to projects only funded through sequencing centers. The Genome Technology piece highlights work at Duke to sequence the genome Cladonia grayi, a lichenized fungus, with 454 technology at Duke’s Institute for Genome Sciences and Policy through their next-gen sequencing program. This is the way of the future where sequencing core facilities will be able to generate sequence only having to wait in the queue at the own university rather than through community sequencing project or sequencing center proposal queues.

This isn’t the only lichen being sequenced. Xanthoria parietina is also in the queue at JGI, but has taken a while to get going because of some logistical problems getting the DNA (and any problems are amplified because it takes a long time to get new material since lichens grow very slow).

The transfer of the power for researchers to be able to quick exploratory whole-genome sequencing with next-gen and eventually, high quality genome sequences from next-gen sequencing is predicted to transform how this kind of science gets done. It means we’ll probably just sequence a mutant strain instead of trying to map the mutation – this is happening already in anecdotal stories in worms and in our work in mushrooms. N.B. this is done after a mutagenized strain has been cleaned up a bit to insure we’re looking for one or only a few mutations based on some crosses – but that is part of standard genetic approaches anyways.

This fast,cheap,whole-genome-sequencing is also the stuff of personal genomics, but for basic research it will also mean that a first pass exploring gene repertoire of an organism will be a multi-week instead of multi-year project. I just hope we’re training enough people who can efficiently extract the information from all this data with solid bioinformatics, computational, data-oriented programming, and statistical skills to support all the labs that will want to take this approach. You’ll need a life-vest to swim in the big data pool for a while until more tools are developed that can be deployed by non-experts.

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

Yes, Ecology can improve Genomics

Blogging on Peer-Reviewed ResearchFew organisms are as well understood at the genetic level as Saccharomyces cerevisiae. Given that there are more yeast geneticists than yeast genes and exemplary resources for the community (largely a result of their size), this comes as no surprise. What is curious is the large number of yeast genes for which we’ve been unable to characterize. Of the ~6000 genes currently identified in the yeast genome, 1253 have no verified function (for the uninclined, this is roughly 21% of the yeast proteome). Egads! If we can’t figure this out in yeast, what hope do we have in non-model organisms?Lourdes Peña-Castillo and Timothy R. Hughes discuss this curious observation and its cause in their report in Genetics.

Continue reading Yes, Ecology can improve Genomics

Fusarium graminearum genome published

The genome of the wheat and cereal pathogen Fusarium graminearum was published in Science this week in an article entitled “The Fusarium graminearum Genome Reveals a Link Between Localized Polymorphism and Pathogen Specializationtion”. The project was a collaboration of many different Fusarium research groups. The genome sequencing was spearheaded by the Broad Institute at Harvard and MIT and is part of a larger project to sequence several different species of Fusarium. The group sequenced a second strain in order to identify polymorphisms.

Some of the key findings

  • The presence of Repeat Induced point-mutation (RIP) has likely limited the amount of repetitive and duplicated sequences in the genome
  • Most of the genes unique to F. graminearum (and thus not present in 4 other Fusarium spp genomes) are found in the telomeres
  • Between the sequenced strains SNP density ranged from 0 to 17.5 polymorphisms per kb.
  • Some of the genes expressed uniquely during plant infection (408 total) include known virulence factors and many plant cell-wall degrading enzymes.
  • The genes showing some of the highest SNP diversity tended to be unique to Fusarium and often unique to F. graminearum