An apparent increase in meiotic silencing strength in crosses involving inbred Neurospora crassa strains

Nagasowjanya, T.; Raj, Kranthi B.; Reddy, K. Sreethi; Kasbekar, Durgadas P.

doi:10.1016/j.fgb.2013.05.002

Cited by 6 publications

(4 citation statements)

References 12 publications

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“…A few fungi have been shown to possess the ability to detect unpaired DNA, like the aforementioned transposon, and silence it for the duration of meiosis. In these fungi, the process is called MSUD ( Aramayo and Metzenberg 1996 ; Shiu et al 2001 ; Son et al 2011 ; Nagasowjanya et al 2013 ; Wang et al 2015 ).…”

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confidence: 99%

An RNA Recognition Motif-Containing Protein Functions in Meiotic Silencing by Unpaired DNA

Samarajeewa

Manitchotpisit

Henderson

et al. 2017

G3 Genes|Genomes|Genetics

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Meiotic silencing by unpaired DNA (MSUD) is a biological process that searches pairs of homologous chromosomes (homologs) for segments of DNA that are unpaired. Genes found within unpaired segments are silenced for the duration of meiosis. In this report, we describe the identification and characterization of Neurospora crassa sad-7, a gene that encodes a protein with an RNA recognition motif (RRM). Orthologs of sad-7 are found in a wide range of ascomycete fungi. In N. crassa, sad-7 is required for a fully efficient MSUD response to unpaired genes. Additionally, at least one parent must have a functional sad-7 allele for a cross to produce ascospores. Although sad-7-null crosses are barren, sad-7Δ strains grow at a wild-type (wt) rate and appear normal under vegetative growth conditions. With respect to expression, sad-7 is transcribed at baseline levels in early vegetative cultures, at slightly higher levels in mating-competent cultures, and is at its highest level during mating. These findings suggest that SAD-7 is specific to mating-competent and sexual cultures. Although the role of SAD-7 in MSUD remains elusive, green fluorescent protein (GFP)-based tagging studies place SAD-7 within nuclei, perinuclear regions, and cytoplasmic foci of meiotic cells. This localization pattern is unique among known MSUD proteins and raises the possibility that SAD-7 coordinates nuclear, perinuclear, and cytoplasmic aspects of MSUD.

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confidence: 99%

An RNA Recognition Motif-Containing Protein Functions in Meiotic Silencing by Unpaired DNA

Samarajeewa

Manitchotpisit

Henderson

et al. 2017

G3 Genes|Genomes|Genetics

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“…Theoretically, MSUD should be capable of targeting and inactivating Spk-1 as it is partially unpaired in a killer–sensitive cross; however, MSUD activity has not been evaluated in N. sitophila . MSUD has been shown to have higher efficiency in inbred lines of N. crassa ( 35 ), and we hypothesized that loss of killing could be driven by an increased MSUD activity caused by increased relatedness of the killer and sensitive strains. To test this hypothesis, we generated a strain that lacks functional MSUD by deleting sad-2 ( 36 ) in the sensitive Tahitian strain 4746.…”

Section: Resultsmentioning

confidence: 99%

An introgressed gene causes meiotic drive inNeurospora sitophila

Svedberg

Vogan

Rhoades

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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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.

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“…A mat A and mat a strain pair of the f 10 generation of line 1 (specifically, segregants #1 and #3) are referred to henceforth as B/S1 A and B/S1 a (Figure S2A). A similar schematic diagram illustrating the early crosses (upto the f 8 generation) was presented in Nagasowjanya et al (2013).…”

Section: Methodsmentioning

confidence: 99%

TheNeurospora crassaStandard Oak Ridge Background Exhibits Atypically Efficient Meiotic Silencing by Unpaired DNA

Giri

Pankajam²,

Nishant

et al. 2019

G3 Genes|Genomes|Genetics

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Meiotic silencing by unpaired DNA (MSUD), an RNAi-mediated gene silencing process, is efficient in crosses made in the Neurospora crassa standard Oak Ridge (OR) genetic background. However, MSUD was decidedly less efficient when the OR-derived MSUD testers were crossed with many wild-isolated strains (W), suggesting that either sequence heterozygosity in tester x W crosses suppresses MSUD, or that OR represents the MSUD-conducive extreme in the range of genetic variation in MSUD efficiency. Our results support the latter model. MSUD was less efficient in near-isogenic crosses made in the novel N. crassa B/S1 genetic background, and in N. tetrasperma strain 85. Possibly, in B/S1 and 85, additional regulatory cues, absent from OR, calibrate the MSUD response. A locus in distal chromosome 1R appears to underlie the OR vs. B/S1 difference. Repeat-induced point mutation (RIP) destroys duplicated genes by G:C to A:T mutation of duplicated DNA sequences. Chromosome segment duplications ( Dp s) dominantly suppress RIP, possibly by titrating out the RIP machinery. In Dp x N crosses, the Dp –borne genes cannot pair properly, hence efficient MSUD, as in OR, silences them and renders the crosses barren. We speculate that the increased productivity engendered by inefficient MSUD enables small duplications to escape RIP.

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An apparent increase in meiotic silencing strength in crosses involving inbred Neurospora crassa strains

Cited by 6 publications

References 12 publications

An RNA Recognition Motif-Containing Protein Functions in Meiotic Silencing by Unpaired DNA

An RNA Recognition Motif-Containing Protein Functions in Meiotic Silencing by Unpaired DNA

An introgressed gene causes meiotic drive inNeurospora sitophila

TheNeurospora crassaStandard Oak Ridge Background Exhibits Atypically Efficient Meiotic Silencing by Unpaired DNA

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