DOI

10.30707/1784042475.274785

Document Type

Senior Thesis

Publication Date

Spring 2026

Committee Chair

Thomas Hammond

Committee Member

Fernanda Duque

Abstract

Neurospora crassa is a useful model organism for genetic research due to its haploid life cycle and its ability to produce large numbers of sexual spores called ascospores. The haploid ascospores form within asci, which typically contain eight ascospores at maturity. However, selfish genetic elements known as meiotic gene drivers have been discovered in Neurospora fungi, and some of these alter the number of viable ascospores that form in each ascus. There are two known meiotic gene drivers in N. crassa: Spore killer-2 (Sk-2) and Spore killer-3 (Sk-3). Spore killing occurs when a killer strain mates with a sensitive strain, resulting in the abortion of offspring that do not inherit the killer’s genetic coding. In these crosses, the viable ascospores, which bear the killer genes, are black, while the aborted, inviable ascospores, which lack the killer gene, are white. Offspring inheriting the killer gene also inherit a gene that provides resistance to the killer. This resistance gene makes an antidote to the killer, allowing these offspring to survive. The goals of this study are to 1) refine the location of a gene that controls killing by the Sk-3 spore killer and 2) to investigate how DNA interval deletions near this killer gene impact its function. Towards this goal, I investigated how the deletion of one DNA interval, referred to as i402, affects spore killing in crosses where a genomic defense process called Meiotic Silencing by Unpaired DNA (MSUD) is active and in crosses where MSUD is inactive. MSUD is a genetic mechanism that silences homologous DNA lacking a paired gene during meiosis, and it is thought to protect N. crassa from selfish genetic elements like Sk-3; thus, this thesis should help identify the gene required for killing and help determine how Sk-3 has evolved despite the existence of a defense mechanism that is supposed to prevent its evolution.

Funding Source

This work was supported by the National Science Foundation (Award Number 200595, Elucidating the mechanism of meiotic drive by mRNA editing-mediated spore killing in Neurospora fungi).

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