RIPing in an asexual fungus

ResearchBlogging.orgA.niger conidiophoreA 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.  

The authors discuss this evidence as to whether or not there is a cryptic sexual state that hasn’t been observed or sex has only been lost for a short time in these fungi (the RIP evidence suggests the transposons were RIPed relatively recently).  The mating genes are still present in the genome of A. niger but whether its actively able to complete a sexual cycle (or enough of it to allow for RIPing) still needs to be investigated.

Braumann, I., Berg, M., Kempken, F. (2008). Repeat induced point mutation in two asexual fungi, Aspergillus niger and Penicillium chrysogenum. Current Genetics DOI: 10.1007/s00294-008-0185-y

4 thoughts on “RIPing in an asexual fungus”

  1. Jason,
    Since Colletotrichum genomes and RIP appear to be in the news this week, there is another recent report of a putatively asexual fungus in which RIP was identified — the plant pathogen Colletotrichum cereale, a close relation of C. graminicola (Evolution of transposon repeat-induced point mutation in the genome of Colletotrichum cereale: Reconciling sex, recombination and homoplasy in an ‘‘asexual” pathogen. (2008) Fungal Genet. Biol. 45(3) 190-206. Crouch, et al). The objective of the C. cereale paper was different, but we found the same general situation here as in A. niger — no evidence of a sexual morph for C. cereale (despite ~5 years of attempted crosses in every conceivable combination), but a distinctive RIP signature was identified — and in a lineage specific manner. And in the same issue of FGB, a paper describing how “Mutations in mating-type genes greatly decrease repeat-induced point mutation process in the fungus Podospora anserina” (Arnaise et al, pp 207-220).

  2. Hi, another article that highlight s the presence of RIP in Ophiotomatoid fungi with a method to visualize quickyly the position of RIP mutations on DNA strands.
     
    Characterization of three DNA transposons in the Dutch elm disease fungi and evidence of repeat-induced point (RIP) mutations. Fungal Genet Biol. 2007 May;44(5):430-43. Epub 2006 Dec 16.
     
     

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