Genome quality control: RIP (repeat-induced point mutation) comes to Podospora.

Area of Science:

• Genetics
• Molecular Biology
• Mycology

Background:

• Repeat-induced point mutation (RIP) is a known genomic defense mechanism in *Neurospora crassa*.
• RIP targets duplicated DNA sequences, inducing C-G to T-A mutations, particularly at CpA dinucleotides.
• The occurrence of RIP has been primarily established in *N. crassa*.

Purpose of the Study:

• To investigate the presence and characteristics of RIP-like events in *Podospora anserina*.
• To determine if RIP-like silencing mechanisms extend beyond *N. crassa*.
• To characterize the mutational patterns and genetic alterations associated with this phenomenon in *P. anserina*.

Main Methods:

• Analysis of a *Podospora anserina* strain with a large tandem duplication.
• Sequencing of a 9 kb region within the duplication to identify mutations.
• Comparison of mutation patterns with known RIP mechanisms in *N. crassa*.
• Assessment of DNA methylation levels in the affected regions.

Main Results:

• A significant number of C-G to T-A transitions (106 mutations) were observed in the sequenced region of *P. anserina*.
• Approximately 80% of these mutations occurred at CpA dinucleotides, mirroring RIP specificity.
• The RIP-like event affected at least six genes and extended to single-copy genes within the repeat.
• The process resembled a mild form of RIP, lacking significant C-methylation, unlike in *N. crassa*.

Conclusions:

• Repeat-induced point mutation (RIP), or a light form of it, occurs in *Podospora anserina*.
• This finding demonstrates that RIP-like silencing is not exclusive to *Neurospora crassa*.
• The observed RIP-like event in *P. anserina* is characterized by specific C-G to T-A mutations and reduced C-methylation.