Genome quality control: RIP (repeat-induced point mutation) comes to Podospora.
RIP (repeat-induced point mutation) is a silencing process discovered in Neurospora crassa and so far clearly established only in this species as a currently occurring process. RIP acts premeiotically on duplicated sequences, resulting in C-G to T-A mutations, with a striking preference for CpA/TpG dinucleotides. In Podospora anserina, an RIP-like event was observed after several rounds of sexual reproduction in a strain with a 40 kb tandem duplication resulting from homologous integration of a cosmid in the mating-type region. The 9 kb sequenced show 106 C-G to T-A transitions, with 80% of the replaced cytosines located in CpA dinucleotides. This led to the alteration of at least six genes, two of which were unidentified. This RIP-like event extended to single-copy genes between the two members of the repeat. The overall data show that the silencing process is strikingly similar to a light form of RIP, unaccompanied by C-methylation. Interestingly, the N. crassa zeta-eta sequence, which acts as a potent de novo C-methylation RIP signal in this species, is weakly methylated when introduced into P. anserina. These results demonstrate that RIP, at least in light forms, can occur beyond N. crassa.
Graïa
F
F
Institut de Génétique et Microbiologie, UMR-CNRS 8621, Batiment 400, Université Paris-Sud, 91405 Orsay cedex, France.
Lespinet
O
O
Rimbault
B
B
Dequard-Chablat
M
M
Coppin
E
E
Picard
M
M
D001203:Ascomycota / Q000235:genetics*; D019175:DNA Methylation; D016681:Genome, Fungal; D010641:Phenotype; D017354:Point Mutation; D020080:Tandem Repeat Sequences