The Hyphal Tip

In a letter to the editor to the journal Nature, regarding the recently discovered/induced sexual stage in Aspergillus fumigatus, David Hawksworth argues that using the separate names for sexual (teleomorph) and asexual (anamorph) stages is confusing and unnecessary in this context.  The name Neosartorya fumigata is given to the sexual stage which was produced from two [...]

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Shepard Fairley has gotten alot of notice lately for his Obama art that has been replicated pretty much everywhere. In homage to his earlier street art we’ll discuss the growing Aspergillus genome posse.

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A manuscript at Nature AOP details the success of the Dyer lab and collaborators in encouraging [[Aspergillus fumigatus]] to complete the sexual cycle under observable (e.g. laboratory) conditions. The authors are the teleomorph (sexual or perfect) stage [[Neosartorya fumigata]] for a fungus that had been previously only had an observed anamorphic stage. A. fumigatus can reproduce asexually forming structures called [[conidiophores]] which produce asexual spores called [[conidiospores]] (or mitospores as they are produced via mitosis) define the anamorph or imperfect stage, but no sexual structures such as [[cleistothecia]] that produce the packaged sexual products as [[ascospores]]. See a presentation by David Geiser (archived at the Aspergillus website) for more detail on some of the morphological and phylogenetic characters that unify the group of Eurotiales fungi.

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A quick post of some recent comparative genomics papers on our desk that are worth a look.

Khaldi N, Wolfe KH (2008) Elusive Origins of the Extra Genes in Aspergillus oryzae. PLoS ONE 3(8): e3036. doi:10.1371/journal.pone.0003036. This was a cool but somewhat controversal [...]

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The [[Trichoderma reesei]] genome paper was recently published in Nature Biotechnology from Diego Martinez at [[LANL]] with collaborators at [[JGI]], [[LBNL]], and others. This fungus was chosen for sequencing because it was found on canvas tents eating the cotton material suggesting it may be a good candidate for degrading cellulose plant material as part of cellulosic ethanol production.

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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).

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Another asexual species of fungi also has evidence for the meiosis-specific process of Repeat Induced Point-mutations (RIP).

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Bret has a mold farm of Aspergillus fumigatus in Flight of the Conchords

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A paper in Current Genetics describes the discovery of Repeat Induced Polymorphism (RIP) in two Euriotiales fungi.  RIP has been extensively studied in Neurospora crassa and has been identified in other Sordariomycete fungi Magnaporthe, Fusiarium. This is not the first Aspergillus species to have RIP described as it was demonstrated in the biotech workhorse Aspergillus oryzae.  However, I think this study is the first to describe RIP in a putatively asexual fungus.  The evidence for RIP is only found in transposon sequences in the Aspergillus and Penicillium.  A really interesting aspect of this discovery is RIP is thought to only occur during sexual stage, but a sexual state has never been observed for these fungi.  

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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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