One recommendation that makes the top of the list is an integrated database for fungal genomes, something we’re keenly interested in seeing happen. This sort of centralized repository of functional annotation, literature links, and genome sequences and annotation is critical given the 150+ genomes that are available or on their way. Systematic re-annotation with consistent tools, comparative analyses and gene predictions, and linking gene sequences by homology and ortholog predictions are a critical component to fully utilizing the genomic data that has been produced for the fungi and other organisms.
Scientists at Imperial College London have received almost £350 000 from the Wellcome Trust, the UK’s largest medical research charity, to study Penicillium marneffei, the only Penicillium fungus to cause serious disease in humans. The researchers aim to find out what makes this particular fungus pathogenic.
A paper in Science from Jason Crawford and colleagues explores the function of polyketide synthetases (PKS) in the synthesis of the secondary metabolite and carcinogen aflatoxin. Previous work (nicely reviewed in the fungi by Nancy Keller and colleagues) has shown the the PKS genes have several domains. These domains include acyl carrier protein (ACP), transacylase (SAT), ketosynthase (KS), malonyl-CoA:ACP transacylase (MAT), “product template” PT, Aand thioesterase/Claisen cyclase (TE/CLC). These domains make up PksA, but the specific role of each domain’s in synthesis steps has not been fully worked out. Understanding this process and the specificity of the chemical structures that are created can help in redesign of these enzymes for synthesis of new molecules and drugs.
Then authors cloning and combining the domains from a cDNA template of pksA [accession AY371490] (from Aspergillus parasiticus) into various combinations and then evaluated the synthesized products via HPLC. This deconstruction of a complicated protein and its domains is a great example of functionally mapping the role of each part of the enzyme and integrating with the biochemistry of the synthesized products. The findings of this research also mapped a role for the PT product template domain which could suggest where modifications could be made to tweak the synthesized products by these enzymes.
The following is an announcement to the B.dendrobatidis and fungal community at large from Alan Kuo at JGI. This is the JAM81 strain (Jess Morgan collected from a frog in the California Sierra Nevada). The JEL423 (Joyce Longcore, collected in Panama) strain genome sequence and annotation is available from the Broad Institute.
Please do contact me if you would like to contribute to assigning functions to the annotation. We’re in the last round of analyses for some of the genome work, but if there are particular questions you want to contribute to, we’re open to collaborators and can outline the basis of our work to see how other work can complement it.
The JGI Batrachochytrium annotation portal is now on the public JGI website. As it is public, no password is required.
For those of you who have not yet registered to be an annotator, go to this new link to register.As before, please choose a username that is personal, so that other annotators may be able to recognize it as yours. A derivative of your personal name would be best.
Those of you who are already registered, you do not need to do anything. Your old pre-release username and password are valid on the new public portal too.
As always, please direct all questions and problems to me. Use email or phone: Cheers, Alan.
Some information about the assembly and annotation:
The first annotation of the 127 scaffolds and 24 Mbp of JGI’s 8.74X assembly of the Batrachochytrim dendrobatidis JAM81 genome. We predict 8732 genes, with the following average properties:
Gene length 1825.16 nt
Transcript length 1407.29 nt
Protein length 450.56 aa
Exon frequency 4.29 exons/gene
Exon length 328.37 nt
Intron length 129.18 nt
Gene density 359.1 genes/Mbp scaffold
The genes were found by the following methods:
Total models 8732 (100%)
Jason’s models 3214 (37%)
cDNAs and ESTs 518 (6%)
Similarity to nr 1928 (22%)
ab initio 3072 (35%)
The genes were validated by the following evidence:
start+stop codons 7990 (92%)
EST support 2488 (28%)
nr hit 6787 (78%)
Pfam hit 4329 (50%)
Schmitt, I., Partida-Martinez, L.P., Winkler, R., Voigt, K., Einax, E., DÃ¶lz, F., Telle, S., WÃ¶stemeyer, J., Hertweck, C. (2008). Evolution of host resistance in a toxin-producing bacterialâ€“fungal alliance. The ISME Journal DOI: 10.1038/ismej.2008.19
LEVASSEUR, A. (2008). FOLy: an integrated database for the classification and functional annotation of fungal oxidoreductases potentially involved in the degradation of lignin and related aromatic compounds. Fungal Genetics and Biology DOI: 10.1016/j.fgb.2008.01.004
Shivaji, S., Bhadra, B., Rao, R.S., Pradhan, S. (2008). Rhodotorula himalayensis sp. nov., a novel psychrophilic yeast isolated from Roopkund Lake of the Himalayan mountain ranges, India. Extremophiles DOI: 10.1007/s00792-008-0144-z
Few 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.
A recent paper “Targeted gene deletion in Candida parapsilosis demonstrates the role of secreted lipase in virulence”, from the Nosanchuk lab at Yeshiva University, shows the role of secreted lipases in virulence of this pathogen. C. parapsilosis is second only to the evolutionarily closely related commensal Candida albicans as worldwide cause of invasive candidiasis. This paper demonstrates a knockout system using selectable marker which confers resistance to the drug Nourseothricin. The authors sought to delete the adjacent and convergently-transcribed lipase genes CpLIP1 and CpLIP2 and characterize the phenotype of the lipase deficient mutants as blood-borne C. parapsilosis infections are in a lipid rich environment.
Through a series of experiments testing growth in rich media, media with olive-oil, and in infection models they showed that the importance of lipase activity. The knockout strain was unable to grow efficiently on YNB media+olive oil indicating that these two genes are the only ones capable of lipase activity. The murine infection experiments indicated that the knockout could be cleared in 4 days while the WT and reconstituted were cleared in 7. The authors acknowledge some limitations in the infection model in that it does not fully recapitulate an invasive candidiasis because mice were infected intravenously so the role of endothelial cell invasion was tested in vivo.
The improving genetic tools for targeted disruption of loci in additional species is permitting experiments that get at the heart of what makes some fungi pathogenic. With the genome sequence of many of the relatives of the pathogens we can systematically dissect what genetic differences have a role in virulence. It will be interesting to reconstruct whether the ancestor of many of these Candida spp always had the potential for virulence or if it co-evolved with its human or other mammalian commensal lifestyle.
I’ve never worked with Magnaporthe grisea, the fungus responsible for rice blast, one of the most devastating crop diseases, but I do know that its life cycle is complicated and that knocking out roughly 61% of the genes in the genome and evaluating the mutant phenotype to infer gene function is not trivial. In their recent letter to Nature, Jeon et al did what many of us have dreamed of doing in our fungus of interest: manipulate every gene to find those that contribute to a phenotype of interest.
In their study, the authors looked for pathogenecity genes. Interestingly, the defects in appressorium formation and condiation had the strongest correlation with defects pathogenicity, suggesting that these two developmental stages are crucial for virulence. Ultimately, the authors identify 203 loci involved in pathogenecity, the majority of which have no homologous hits in the sequence databases and have no clear enriched GO functions. Impressively, this constitutes the largest, unbiased list of pathogenecity genes identified for a single species (though so of us, I’m sure, may have a problem with the term “unbiased”).
If you’d like to play with their data, the authors have made it available in their ATMT Database.
A paper by Martin Aslett and Val Wood indicate that the fission yeast community is approaching 100% coverage of a GO annotation for every gene in the S. pombe genome. Only Ashbya gossypii has a smaller genome in the fungi (see a recent paper on Ashbya annotation database) and doesn’t yet have complete GO coverage. This is quite remarkable and a great dataset for studies in S. pombe and all fungi.
My quick predictions of genes a closely related species, S. japonicus, has more than twice as many genes as S. pombe (but be over-prediction by ab initio predictors). Taken in comparison to many other fungi, S. pombe represents a streamlined and reduced genome which probably occured indepdently from reduction in the Hemiascomycetes.
In a recent Microbiology Mini-Review, Meriel Jones catalogs both the potential benefits and problems that arise from fungal genome sequencing. Using the nine genomes (being) sequenced from the Aspergillus clade, Jones addresses several issues tied to a singular theme: if we are to unlock the potential that fungal genome sequencing holds, both academically and entrepreneurially, then a more robust infrastructure that enables comparative and functional annotation of genomes must be established.
Fortunately, like any good awareness advocate, Jones points us in the direction of e-Fungi, a UK based virtual project aimed at setting up such an infrastructure. Anyone can navigate this database to either compare the stored genomic information or evaluate any fungus of interest in the light of the e-Fungi genomic data. The data appears to be precomputed, similar to IMG from JGI, so there are inherent limitations on the data that one can obtain. However, tools such as these put important data in the hands of expert mycologists that can turn the information into something biologically meaningful.
As Jones points out, this is just the beginning. If fungal genomes are to live up to their promise, they must engage more than just experts at reading genomes.