scholarly journals Identification of a genetic element required for spore killing in Neurospora

2018 ◽  
Author(s):  
Nicholas A. Rhoades ◽  
Austin M. Harvey ◽  
Dilini A. Samarajeewa ◽  
Jesper Svedberg ◽  
Aykhan Yusifov ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Meiotic Drive ◽  
Present Evidence ◽  
Partial Duplication ◽  
Genome Defense ◽  
Right Border ◽  
A Genome ◽  
Spore Killing ◽  
The Right ◽  
Spore Killer

ABSTRACTMeiotic drive elements like Spore killer-2 (Sk-2) in Neurospora are transmitted through sexual reproduction to the next generation in a biased manner. Sk-2 achieves this biased transmission through spore killing. Here, we identify rfk-1 as a gene required for the spore killing mechanism. The rfk-1 gene is associated with a 1,481 bp DNA interval (called AH36) near the right border of the 30 cM Sk-2 element, and its deletion eliminates the ability of Sk-2 to kill spores. The rfk-1 gene also appears to be sufficient for spore killing because its insertion into a non-Sk-2 isolate disrupts sexual reproduction after the initiation of meiosis. Although the complete rfk-1 transcript has yet to be defined, our data indicate that rfk-1 encodes a protein of at least 39 amino acids and that rfk-1 has evolved from a partial duplication of gene ncu07086. We also present evidence that rfk-1’s location near the right border of Sk-2 is critical for the success of spore killing. Increasing the distance of rfk-1 from the right border of Sk-2 causes it to be inactivated by a genome defense process called meiotic silencing by unpaired DNA (MSUD), adding to accumulating evidence that MSUD exists, at least in part, to protect genomes from meiotic drive.

scholarly journals An introgressed gene causes meiotic drive in Neurospora sitophila

2021 ◽  
Vol 118 (17) ◽  
pp. e2026605118
Author(s):  
Jesper Svedberg ◽  
Aaron A. Vogan ◽  
Nicholas A. Rhoades ◽  
Dilini Sarmarajeewa ◽  
David J. Jacobson ◽  
...  
Keyword(s):  
Natural Populations ◽  
Meiotic Drive ◽  
Reading Frame ◽  
Origin And Evolution ◽  
Filamentous Ascomycete ◽  
Genome Defense ◽  
Genome Wide ◽  
A Genome ◽  
Spore Killing ◽  
Spore Killer

Meiotic drive elements cause their own preferential transmission following meiosis. In fungi, this phenomenon takes the shape of spore killing, and in the filamentous ascomycete Neurospora sitophila, the Sk-1 spore killer element is found in many natural populations. In this study, we identify the gene responsible for spore killing in Sk-1 by generating both long- and short-read genomic data and by using these data to perform a genome-wide association test. We name this gene Spk-1. Through molecular dissection, we show that a single 405-nt-long open reading frame generates a product that both acts as a poison capable of killing sibling spores and as an antidote that rescues spores that produce it. By phylogenetic analysis, we demonstrate that the gene has likely been introgressed from the closely related species Neurospora hispaniola, and we identify three subclades of N. sitophila, one where Sk-1 is fixed, another where Sk-1 is absent, and a third where both killer and sensitive strain are found. Finally, we show that spore killing can be suppressed through an RNA interference-based genome defense pathway known as meiotic silencing by unpaired DNA. Spk-1 is not related to other known meiotic drive genes, and similar sequences are only found within Neurospora. These results shed light on the diversity of genes capable of causing meiotic drive, their origin and evolution, and their interaction with the host genome.

scholarly journals Combinations of Spok genes create multiple meiotic drivers in Podospora

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Aaron A Vogan ◽  
S Lorena Ament-Velásquez ◽  
Alexandra Granger-Farbos ◽  
Jesper Svedberg ◽  
Eric Bastiaans ◽  
...  
Keyword(s):  
Gene Family ◽  
Sexual Reproduction ◽  
Phylogenetic Analyses ◽  
Natural Populations ◽  
Meiotic Drive ◽  
Kinase Domain ◽  
Podospora Anserina ◽  
Spore Killing ◽  
Different Strains ◽  
Spore Killer

Meiotic drive is the preferential transmission of a particular allele during sexual reproduction. The phenomenon is observed as spore killing in multiple fungi. In natural populations of Podospora anserina, seven spore killer types (Psks) have been identified through classical genetic analyses. Here we show that the Spok gene family underlies the Psks. The combination of Spok genes at different chromosomal locations defines the spore killer types and creates a killing hierarchy within a population. We identify two novel Spok homologs located within a large (74–167 kbp) region (the Spok block) that resides in different chromosomal locations in different strains. We confirm that the SPOK protein performs both killing and resistance functions and show that these activities are dependent on distinct domains, a predicted nuclease and kinase domain. Genomic and phylogenetic analyses across ascomycetes suggest that the Spok genes disperse through cross-species transfer, and evolve by duplication and diversification within lineages.

scholarly journals An introgressed gene causes meiotic drive in Neurospora sitophila

2020 ◽  
Author(s):  
Jesper Svedberg ◽  
Aaron A. Vogan ◽  
Nicholas A. Rhoades ◽  
Dilini Sarmarajeewa ◽  
David J. Jacobson ◽  
...  
Keyword(s):  
Rna Interference ◽  
Natural Populations ◽  
Meiotic Drive ◽  
Host Genome ◽  
Origin And Evolution ◽  
Filamentous Ascomycete ◽  
Selfish Genes ◽  
A Genome ◽  
Spore Killing ◽  
Spore Killer

AbstractMeiotic drive elements cause their own preferential transmission following meiosis. In fungi this phenomenon takes the shape of spore killing, and in the filamentous ascomycete Neurospora sitophila, the Sk-1 spore killer element is found in many natural populations. In this study, we identify the gene responsible for spore killing in Sk-1 by generating both long and short-read genomic data and by using these data to perform a genome wide association test. Through molecular dissection, we show that a single 405 nucleotide long open reading frame generates a product that both acts as a poison capable of killing sibling spores and as an antidote that rescues spores that produce it. By phylogenetic analysis, we demonstrate that the gene is likely to have been introgressed from the closely related species N. hispaniola, and we identify three subclades of N. sitophila, one where Sk-1 is fixed, another where Sk-1 is absent, and a third where both killer and sensitive strain are found. Finally, we show that spore killing can be suppressed through an RNA interference based genome defense pathway known as meiotic silencing by unpaired DNA. Spk-1 is not related to other known meiotic drive genes, and similar sequences are only found within Neurospora. These results shed new light on the diversity of genes capable of causing meiotic drive, their origin and evolution and their interaction with the host genome.Significance StatementIn order to survive, most organisms have to deal with parasites. Such parasites can be other organisms, or sometimes, selfish genes found within the host genome itself. While much is known about parasitic organisms, the interaction with their hosts and their ability to spread within and between species, much less is known about selfish genes. We here identify a novel selfish “spore killer” gene in the fungus Neurospora sitophila. The gene appears to have evolved within the genus, but has entered the species through hybridization and introgression. We also show that the host can counteract the gene through RNA interference. These results shed new light on the diversity of selfish genes in terms of origin, evolution and host interactions.

scholarly journals RNA editing controls meiotic drive by a Neurospora Spore killer

2021 ◽  
Author(s):  
Nicholas A. Rhoades ◽  
Thomas M. Hammond
Keyword(s):  
Amino Acid ◽  
Rna Editing ◽  
Stop Codon ◽  
Meiotic Drive ◽  
Transmission Mechanism ◽  
Mrna Editing ◽  
Vegetative Tissue ◽  
Spore Killing ◽  
Protein Variants ◽  
Spore Killer

ABSTRACTNeurospora Sk-2 is a complex meiotic drive element that is transmitted to offspring through sexual reproduction in a biased manner. Sk-2’s biased transmission mechanism involves spore killing, and recent evidence has demonstrated that spore killing is triggered by a gene called rfk-1. However, a second gene, rsk, is also critically important for meiotic drive by spore killing because it allows offspring with an Sk-2 genotype to survive the toxic effects of rfk-1. Here, we present evidence demonstrating that rfk-1 encodes two protein variants: a 102 amino acid RFK-1A and a 130 amino acid RFK-1B, but only RFK-1B is toxic. We also show that expression of RFK-1B requires an early stop codon in rfk-1 mRNA to undergo adenosine-to-inosine (A-to-I) mRNA editing. Finally, we demonstrate that RFK-1B is toxic when expressed within vegetative tissue of Spore killer sensitive (SkS) strains, and that this vegetative toxicity can be overcome by co-expressing Sk-2’s version of RSK. Overall, our results demonstrate that Sk-2 uses RNA editing to control when its spore killer is produced, and that the primary killing and resistance functions of Sk-2 can be conferred upon an SkS strain by the transfer of only two genes.

scholarly journals Spore-Killing Meiotic Drive Factors in a Natural Population of the Fungus Podospora anserina

Genetics ◽  
2000 ◽  
Vol 156 (2) ◽  
pp. 593-605 ◽  
Author(s):  
Marijn van der Gaag ◽  
Alfons J M Debets ◽  
Jessica Oosterhof ◽  
Marijke Slakhorst ◽  
Jessica A G M Thijssen ◽  
...  
Keyword(s):  
Linkage Group ◽  
The Netherlands ◽  
Natural Population ◽  
Local Population ◽  
Meiotic Drive ◽  
Podospora Anserina ◽  
Group Iii ◽  
Spore Killing ◽  
Different Types ◽  
Spore Killer

Abstract In fungi, meiotic drive is observed as spore killing. In the secondarily homothallic ascomycete Podospora anserina it is characterized by the abortion of two of the four spores in the ascus. We have identified seven different types of meiotic drive elements (Spore killers). Among 99 isolates from nature, six of these meiotic drive elements occurred in a local population. Spore killers comprise 23% of the natural population of P. anserina in Wageningen, The Netherlands, sampled from 1991 to 1997. One Spore-killer type was also found in a French strain dating from 1937. All other isolates found so far are sensitive to spore killing. All seven Spore killer types differ in the percentage of asci that show killing and in their mutual interactions. Interactions among Spore killer types showed either mutual resistance or dominant epistasis. Most killer elements could be assigned to linkage group III but are not tightly linked to the centromere.

scholarly journals A meiotic drive element in the maize pathogenFusarium verticillioidesis located within a 102-kb region of chromosome V

2016 ◽  
Author(s):  
Jay Pyle ◽  
Tejas Patel ◽  
Brianna Merril ◽  
Chabu Nsokoshi ◽  
Morgan McCall ◽  
...  
Keyword(s):  
Mapping Population ◽  
Fusarium Verticillioides ◽  
Meiotic Drive ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
Toxic Compounds ◽  
Hypervariable Regions ◽  
Spore Killing ◽  
Spore Killer ◽  
Extra Gene

ABSTRACTFusarium verticillioidesis an agriculturally important fungus because of its association with maize and its propensity to contaminate grain with toxic compounds. Some isolates of the fungus harbor a meiotic drive element known as Sporekiller(SkK) that causes nearly all surviving meiotic progeny from anSkK× Spore killer-susceptible (SkS) cross to inherit theSkKallele.SkKhas been mapped to chromosome V but the genetic element responsible for meiotic drive and spore killing has yet to be identified. In this study, we used cleaved amplified polymorphic sequence markers to genotype individual progeny from anSkK×SkSmapping population. We also sequenced the genomes of three progeny from the mapping population to determine their single nucleotide polymorphisms. These techniques allowed us to refine the location ofSkKto a contiguous 102-kb region of chromosome V, herein referred to as theSklocus. Relative toSkSgenotypes,SkKgenotypes have one extra gene within this locus for a total of 42 genes. The additional gene inSkKgenotypes, named SKL1 forSpore Killer Locus 1, is the most highly expressed gene from theSklocus during early stages of sexual development. TheSklocus also has three hypervariable regions, the longest of which includesSKL1. The possibility thatSKL1, or another gene from theSklocus, is an essential component of meiotic drive and spore killing is discussed.

scholarly journals The role of prefrontal cortex in working memory: examining the contents of consciousness

1998 ◽  
Vol 353 (1377) ◽  
pp. 1819-1828 ◽  
Author(s):  
◽  
S. M. Courtney ◽  
L. Petit ◽  
J. V. Haxby ◽  
L. G. Ungerleider
Keyword(s):  
Working Memory ◽  
Prefrontal Cortex ◽  
Visual Processing ◽  
Right Hemisphere ◽  
Functional Organization ◽  
Spatial Working Memory ◽  
Domain Specificity ◽  
Long Term Memory ◽  
Present Evidence ◽  
The Right

Working memory enables us to hold in our ‘mind's eye’ the contents of our conscious awareness, even in the absence of sensory input, by maintaining an active representation of information for a brief period of time. In this review we consider the functional organization of the prefrontal cortex and its role in this cognitive process. First, we present evidence from brain–imaging studies that prefrontal cortex shows sustained activity during the delay period of visual working memory tasks, indicating that this cortex maintains on–line representations of stimuli after they are removed from view. We then present evidence for domain specificity within frontal cortex based on the type of information, with object working memory mediated by more ventral frontal regions and spatial working memory mediated by more dorsal frontal regions. We also propose that a second dimension for domain specificity within prefrontal cortex might exist for object working memory on the basis of the type of representation, with analytic representations maintained preferentially in the left hemisphere and image–based representations maintained preferentially in the right hemisphere. Furthermore, we discuss the possibility that there are prefrontal areas brought into play during the monitoring and manipulation of information in working memory in addition to those engaged during the maintenance of this information. Finally, we consider the relationship of prefrontal areas important for working memory, both to posterior visual processing areas and to prefrontal areas associated with long–term memory.

scholarly journals The Mind In Its Own Place: The Difficulties and Benefits of Thinking for Pleasure

2019 ◽  
Author(s):  
Timothy D. Wilson ◽  
Erin Corwin Westgate ◽  
Nick Buttrick ◽  
Daniel Gilbert
Keyword(s):  
Positive Affect ◽  
Intervention Study ◽  
Present Evidence ◽  
Trade Off ◽  
Everyday Lives ◽  
The Right ◽  
The Mind ◽  
Is Value

This chapter is concerned with a type of thinking that has received little attention, namely intentional “thinking for pleasure”—the case in which people deliberately focus solely on their thoughts with the goal of generating positive affect. We present a model that describes why it is difficult to enjoy one's thoughts, how it can be done successfully, and when there is value in doing so. We review 36 studies we have conducted on this topic with just over 10,000 participants. We found that thinking for pleasure does not come easily to most people, but can be enjoyable and beneficial under the right conditions. Specifically, we found evidence that thinking for pleasure requires both motivation and the ability to concentrate. For example, several studies show that people enjoy thinking more when it is made easier with the use of “thinking aids.” We present evidence for a trade-off model that holds that people are most likely to enjoy their thoughts if they find those thoughts to be personally meaningful, but that such thinking involves concentration, which lowers enjoyment. Lastly, we review evidence for the benefits of thinking for pleasure, including an intervention study in which participants found thinking for pleasure enjoyable and meaningful in their everyday lives.

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