Genetic and Molecular Dissection of Meiotic Silencing by Unpaired DNA

An extra DNA segment often indicates the presence of a virus or some other foreign DNA. Accordingly, organisms normally maintain defense systems to silence (turn off) the gene expression from this potential intruder. In the model fungus Neurospora crassa (an orange bread mold), a defense system operates during the sexual cycle to minimize the production from an unpaired gene.

It is called Meiotic Silencing by Unpaired DNA (MSUD), and it utilizes an RNA-based gene silencing system to single out its targets. The goal of this project is to better understand the mechanism behind the MSUD pathway. Since DNA segments lacking a pairing partner are also targeted in worms, mice, and humans, this project will shed light on how DNA pairing could affect gene regulation in a variety of organisms.

The investigators will recruit and train undergraduates through different campus student success programs. Research activities from this project will be used to develop lesson modules for lab tours and outreach visits to a local elementary school. Efforts will also be made to promote scientific literacy, interdisciplinary partnership, and STEM (Science, Technology, Engineering, and Mathematics) education.

In many organisms, robust genome surveillance mechanisms are used to keep transposons and other selfish elements from spreading. One example is the MSUD pathway, which is first described in the filamentous fungus N. crassa. In this pathway, an unpaired gene generates a silencing signal (in the form of small interfering RNAs), which subsequently turns off the expression of this unpaired DNA as well as any other copies in the genome.

MSUD utilizes Argonaute and other common RNA interference (RNAi) proteins to suppress the expression of its targets. Using the tools they have developed (e.g., silencing mutants, cellular markers, gene placement systems, and various assays), the investigators will characterize the phenotypes of silencing-deficient mutants and investigate the interactions and specific roles of MSUD components.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.