skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Studying A Spore Killing Gene in Neurospora crassa
Some isolates of the fungus Neurospora crassa possess a chromosomal factor that causes spore killing, leading to death of ascospores. It has been shown that these chromosomal factors are genetic elements called spore killers. For example, if a cross is performed between a parent with an Sk-S (sensitive) allele and a parent with an Sk-K (killer) allele, the cross will produce half viable offspring and half inviable offspring, where the inviable half has been killed by spore killing. This phenomenon can be explained by meiotic drive, wherein a selfish gene disrupts the randomness of sexual transmission, favoring its own success. In this study, I focus on a Neurospora Spore killer known as Sk-3. Sk-3 is thought to possess both a killer element and a resistance element. The resistance element is rsk, a gene that keeps ascospores alive and viable when in the presence of the killer element. However, the mechanism by which the killer element kills ascospores is unknown. A major obstacle to studying the killing mechanism is that the identity of the Sk-3 killer element itself has remained elusive. My goal is to help identify the Sk-3 killer element. Preliminary results by others have narrowed the search to the left arm of Chromosome III. These results have also shown that deletion of a 1.3 kb DNA interval, called v350, causes loss of spore killing. This suggests that a regulatory element, or a hidden gene, may overlap with the v350 interval. To help determine why v350 deletion correlates with loss of spore killing, I investigated a related DNA interval, called v384. My results suggest that v384, like v350, is required for spore killing.  more » « less
Award ID(s):
2005295
PAR ID:
10649509
Author(s) / Creator(s):
Publisher / Repository:
ISU ReD: Research and eData
Date Published:
Subject(s) / Keyword(s):
Senior Thesis
Format(s):
Medium: X
Institution:
Illinois State University
Sponsoring Org:
National Science Foundation
More Like this
  1. (, ISU ReD: Research and eData)
    In Neurospora fungi, the ascospores formed during reproduction will most often be black and viable. Occasionally, these ascospores will end up inviable and white or yellow. The discovery of a selfish genetic element called Spore killer (Sk) in 1979 gave researchers insight into a mechanism that causes some Neurospora crosses to produce a consistent ratio of 4 black, viable ascospores and 4 inviable, white ascospores. In these 4:4 splits, the Spore killer genetic element causes the death of exactly half of the ascospores. There are now three known spore killers in Neurospora: Sk-1, Sk-2, and Sk-3. This thesis examines the role of a DNA element within Sk-3. In an Sk-3 × Sk-3-sensitive (Sk-S) cross, Sk-3 genes are transmitted to the four black, viable ascospores, and, through a poorly understood mechanism, the Sk-3 genes kill ascospores that fail to inherit these genes. The Sk-3 genes reside on Chromosome III, but the exact locations of all critical genes are unknown. Preliminary results suggest that a DNA interval called v350 may harbor a critical Sk-3 gene. For example, deletion of the v350 interval eliminates Sk-3 spore killing. Here, I explore the deletion of an additional DNA interval located within v350. Specifically, I tested the role of DNA interval v376 on Sk-3 spore killing. The research presented here should help determine why v350, and perhaps v376, are required for spore killing by Neurospora Sk-3. 
    more » « less
  2. (, ISU ReD)
    Neurospora fungi are found around the world. The species N. crassa is a popular model for use in genetics research. N. crassa produces sexual spores, called ascospores, during mating between strains of opposite mating types. N. crassa also produces spore sacs called asci, and each ascus typically contains eight viable ascospores. However, some Neurospora fungi carry selfish genetic elements called Spore killers, and when a strain carrying a Spore killer mates with a spore killing-susceptible strain, asci contain four black viable ascospores and four white inviable ascospores. In this project, I investigated a Spore killer called Sk-3. To act as a selfish genetic element, Sk-3 is thought to require at least two genes, a poison gene and an antidote gene. The Sk-3 antidote gene (rsk) has been identified, but the poison gene has not. The purpose of this study is to help identify the location of the poison gene. To do this, I deleted two DNA intervals (i383 and i394) from a location of the Neurospora genome that may harbor the poison gene. My results indicate that deletion of i383 eliminates spore killing while deletion of i394 has no effect on spore killing. The possibility that i394 overlaps with the poison gene is discussed. 
    more » « less
  3. (, ISU ReD: Research and eData)
    Meiotic drive is a non-Mendelian inheritance phenomenon where selfish genetic elements change gene transmission in their own favor. This phenomenon occurs in the fungus Neurospora crassa during spore killing. When a strain carrying a spore killer genetic element is crossed with a non-spore killing wild type strain, the cross will produce half viable and half inviable offspring. The N. crassa Sk-3 spore killer is found on Chromosome III. Sk-3 is one of the most studied meiotic drive elements in Neurospora fungi and it is thought to require a killer gene and a resistance gene for spore killing. While the killer gene has not been identified, recent work has isolated a mutation (rfk-2UV) that disrupts spore killing. Although this mutation has been mapped to Chromosome III, its exact location is not known. In this work, I investigate the role of one DNA interval in Sk-3-based spore killing. This DNA interval, referred to as v373, is thought to reside within or near rfk-2UV. My results will contribute to future efforts to identify the Sk-3 killer gene. 
    more » « less
  4. (, ISU ReD: Research and eData)
    Neurospora crassa is a fungus that serves as a model organism for genetic research. N. crassa Spore killer-3 (Sk-3) is a genetic element transmitted to offspring through spore killing. Sk-3 is located on Chromosome III and it is thought to require two genes for spore killing. These two genes are the poison gene, for killing, and the antidote gene, for resistance to killing. While the Sk-3 resistance gene has been identified (rsk), the Sk-3 killer gene has not. The primary goal of this study is to help identify the killer gene by investigating the role of a DNA interval called v377 in spore killing. To determine if this interval is required for spore killing, a DNA deletion vector (Vector v377) was constructed and used to replace the v377 interval with a hygromycin resistance gene in strain RDGR170.3. My results demonstrate that v377 is required for spore killing. The possibility that v377 is within a gene required for spore killing, or a regulatory element that controls spore killing, is discussed. 
    more » « less
  5. (, ISU ReD: Research and eData)
    Meiotic drive describes a process in which selfish alleles are recovered in more than half of a progeny generation. It is a type of gene drive and it has been discovered in strains of Neurospora, a filamentous fungus, through its spore killing mechanism. One of the most studied meiotic drive elements within N. crassa is Spore killer-3 (Sk-3). Previous studies have indicated that there is a genomic region within Sk-3 that encodes resistance to spore killing and another that encodes an element that is required for spore killing. Sk-3’s resistance gene, rsk, has been identified. However, the exact region that mediates Sk-3’s spore killing mechanism is currently unknown. In a previous study, it was found that a mutation called rfk-2UV disrupts spore killing by Sk-3. To better understand the region of Chromosome III in which rfk-2UV is located (its exact location is unknown), I constructed a deletion vector to replace a DNA interval (v374) with a hygromycin resistance gene marker (hph). Transformants were crossed to produce offspring, and offspring were tested to determine if they possess the ability to kill ascospores. These findings will contribute to future efforts to determine the molecular nature of rfk-2UV and why this mutation disrupts the ability of Sk-3 to kill spores. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email