An NCBP3-Domain Protein Mediates Meiotic Silencing by Unpaired DNA

A DEAD-box RNA helicase mediates meiotic silencing by unpaired DNA

During the sexual phase of Neurospora crassa, unpaired genes are subject to a silencing mechanism known as meiotic silencing by unpaired DNA (MSUD). MSUD targets the transcripts of an unpaired gene and utilizes typical RNA interference factors for its process. Using a reverse genetic screen, we have identified a meiotic silencing gene called sad-9, which encodes a DEAD-box RNA helicase. While not essential for vegetative growth, SAD-9 plays a crucial role in both sexual development and MSUD. Our results suggest that SAD-9, with the help of the SAD-2 scaffold protein, recruits the SMS-2 Argonaute to the perinuclear region, the center of MSUD activity.

Gene drive by Fusarium SKC1 is dependent on its competing allele

The Fusarium verticillioides SKC1 gene driver is transmitted to offspring in a biased manner through spore killing. The mechanism that allows SKC1 to kill non-SKC1 offspring while sparing others is poorly understood. Here we report that gene drive by SKC1 is dependent on SKC1's competing allele. We propose that SKC1's competing allele influences the ability of a genome defense process to detect SKC1, and we provide evidence that this genome defense process is meiotic silencing by unpaired DNA (MSUD). Our findings suggest that the successful deployment of gene drivers to control pathogenic fungi will require researchers to consider how competing alleles influence the ability of gene drivers to be detected by genome defense processes.

Involvement of RNA granule proteins in meiotic silencing by unpaired DNA

In Neurospora crassa, expression from an unpaired gene is suppressed by a mechanism known as meiotic silencing by unpaired DNA (MSUD). MSUD utilizes common RNA interference (RNAi) factors to silence target mRNAs. Here, we report that Neurospora CAR-1 and CGH-1, homologs of two Caenorhabditis elegans RNA granule components, are involved in MSUD. These fungal proteins are found in the perinuclear region and P-bodies, much like their worm counterparts. They interact with components of the meiotic silencing complex (MSC), including the SMS-2 Argonaute. This is the first time MSUD has been linked to RNA granule proteins.