DOI

10.30707/1777915859.023576

Document Type

Senior Thesis

Publication Date

Fall 2025

Committee Chair

Thomas Hammond

Committee Member

Kevin Edwards

Abstract

The selfish genetic element Spore killer-3 (Sk-3) is found in some Neurospora fungi. Sk-3 is considered selfish because it has evolved the capacity to bias its transmission to the next generation through spore killing. The mechanism of spore killing requires at least two genes, a gene that produces a resistance protein (an antidote) and a gene that produces a killer protein (a poison). The Sk-3 genetic element is millions of base pairs long and contains hundreds of genes. Although the antidote gene has been identified, the identity of the poison gene has remained elusive. Previous research has identified a DNA interval (i350) within the Sk-3 element as critical for the spore killing mechanism. Protein coding sequences have yet to be detected within the interval, but it is located only 500 bp from the start codon of a gene called ncu07872. In this thesis, I sought to determine if ncu07872 is required for spore killing. I tested this hypothesis by deleting an interval called i358, which spans ncu07872 but does not overlap with i350. I recovered six candidate i358Δ strains and successfully performed spore killing assays on four of the candidates. All four candidates demonstrated a spore killing phenotype when crossed with standard tester strains, suggesting that ncu07872 is not required for spore killing and, thus, does not encode Sk-3's poison gene. This hypothesis is supported by my genotyping results, which are consistent with deletion of ncu07872 from the genomes of the tested strains. In summary, my research indicates that ncu07872 is not required for spore killing and that the nearby element within i350 that is required for spore killing works independently of ncu07872.

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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