Repeat induced point mutation in two asexual fungi, Aspergillus niger and Penicillium chrysogenum.
Repeat induced point mutation (RIP) is a gene silencing mechanism present in fungal genomes. During RIP, duplicated sequences are efficiently and irreversibly mutated by transitions from C:G to T:A. For the first time, we have identified traces of RIP in transposable elements of Aspergillus niger and Penicillium chrysogenum, two biotechnologically relevant fungi. We found that RIP in P. chrysogenum has affected a large set of sequences, which also contain other mutations. On the other hand, RIP in A. niger is limited to only few sequences, but literally all mutations are RIP-like. Surprisingly, RIP occurred only in transposon sequences that have disrupted open reading frames in A. niger, a phenomenon not yet reported for other fungi. In both fungal species, we identified two sequences with strong sequence similarity to Neurospora crassa RID. RID is a putative DNA methyltransferase and the only known enzyme involved in the RIP process. Our findings suggest that both A. niger and P. chrysogenum either had a sexual past or have a sexual potential. These findings have important implications for future strain development of these fungi.
Braumann
Ilka
I
Abteilung Botanik mit Schwerpunkt Genetik und Molekularbiologie, Botanisches Institut und Botanischer Garten, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel, Germany.
van den Berg
Marco
M
Kempken
Frank
F
D000595:Amino Acid Sequence; D001234:Aspergillus niger / Q000235:genetics*; D001483:Base Sequence; D015254:DNA Modification Methylases / Q000235:genetics; D004251:DNA Transposable Elements / Q000502:physiology*; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010408:Penicillium chrysogenum / Q000235:genetics*; D010802:Phylogeny; D017354:Point Mutation / Q000502:physiology; D012100:Reproduction, Asexual / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid
D004251:DNA Transposable Elements; D015254:DNA Modification Methylases