Meiotic silencing by unpaired DNA is expressed more strongly in the early than the late perithecia of crosses involving most wild-isolated Neurospora crassa strains and in self-crosses of N. tetrasperma

Ramakrishnan, Mukund; Sowjanya, T. Naga; Raj, Kranthi B.; Kasbekar, Durgadas P.

doi:10.1016/j.fgb.2011.10.002

Cited by 18 publications

(19 citation statements)

References 20 publications

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“…The two ::r3 B/S1 x ::r3 OR crosses produced < 4% round ascospores, showing that the MSUD machinery recognized the ::r3 B/S1 and ::r3 OR transgenes as alleles (paired). The ::r3 OR x B/S1 and ::r3 B/S1 x OR crosses produced 25-64 % round ascospores, which was consistent with the results of Ramakrishnan et al (2011) showing MSUD is inefficient in crosses of the OR-derived MSUD testers with the Bichpuri-1 and Spurger-3 strains, from which the B/S1 strains are derived. The ::r3 B/S1 x B/S1 crosses produced < 24% round ascospores, which was inconsistent with model 1.…”

Section: Resultssupporting

confidence: 87%

“…MSUD is also much less efficient in the N. tetrasperma strain 85 background (Jacobson et al, 2008;Ramakrishnan et al, 2011). Specifically, self-cross of an 85-derived [::asm-1 + WT] dikaryotic strain produced < 76% MSUD-induced white-spored asci whereas comparable crosses in the OR background produced >99% white-spored asci (Ramakrishnan et al, 2011), thus the 85 background can be thought of as Sad-or Esm-type. We have now introgressed an ::r transgene from N. crassa OR into N. tetrasperma 85, and the resulting ::r Nt testers were used to make ::r Nt x 85 crosses.…”

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confidence: 99%

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TheNeurospora crassastandard Oak Ridge background exhibits an atypically efficient meiotic silencing by unpaired DNA

Giri

Pankajam

Nishant

et al. 2018

Preprint

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Meiotic silencing by unpaired DNA (MSUD) was discovered in crosses made in the standard Oak Ridge (OR) genetic background of Neurospora crassa. However, MSUD often was decidedly less efficient when the OR-derived MSUD tester strains were crossed with wild-isolated strains (W), which suggested either that 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 much less efficient in near-isogenic crosses made in a novel N. crassa B/S1 and the N. tetrasperma 85 genetic backgrounds. Possibly, regulatory cues that in other genetic backgrounds calibrate the MSUD response are missing from OR. The OR versus B/S1 difference appears to be determined by loci on chromosomes 1, 2, and 5. OR crosses heterozygous for a duplicated chromosome segment (Dp) have for long been known to exhibit an MSUD-dependent barren phenotype. However, inefficient MSUD in N. tetrasperma 85 made Dp-heterozygous crosses non-barren. This is germane to our earlier demonstration that Dps can act as dominant suppressors of repeat-induced point mutation (RIP). Occasionally, during ascospore partitioning rare asci contained >8 nuclei, and round ascospores dispersed less efficiently than spindle-shaped ones.General abstractIn crosses made in the standard OR genetic background of Neurospora crassa, an RNAi-mediated process called MSUD efficiently silences any gene not properly paired with its homologue during meiosis. We found that MSUD was not as efficient in comparable crosses made in the N. crassa B/S1 and N. tetrasperma 85 backgrounds, suggesting that efficient MSUD is not necessarily the norm in Neurospora. Indeed, using OR strains for genetic studies probably fortuitously facilitated the discovery of MSUD and its suppressors. As few as three unlinked loci appear to underlie the OR versus B/S1 difference in MSUD.

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Section: Resultssupporting

confidence: 87%

mentioning

confidence: 99%

TheNeurospora crassastandard Oak Ridge background exhibits an atypically efficient meiotic silencing by unpaired DNA

Giri

Pankajam

Nishant

et al. 2018

Preprint

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“…Most Esm type strains gave a fertile cross with Dp(EB4) and a barren cross with Dp(IBj5) , although some Esm type gave barren crosses with both the Dp s, and fewer still gave fertile crosses with them. Other results of Ramakrishnan et al . (2011) suggested that N. tetrasperma strain 85 is Esm type.…”

Section: Introductionmentioning

confidence: 55%

“…Ramakrishnan et al . (2011) classified wild-isolated N. crassa strains into three types based on the strength of MSUD in their crosses with tester strains, namely, “OR” (which includes the standard laboratory strains OR A and OR a ), “Sad” (which includes the semi-dominant Sad suppressors of MSUD obtained from the OR background), and “Esm”.…”

Section: Introductionmentioning

confidence: 99%

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Neurospora heterokaryons with complementary duplications and deficiencies in their constituent nuclei provide an approach to identify nucleus-limited genes

Giri

Rekha

Kasbekar

2015

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Introgression is the transfer of genes or genomic regions from one species into another via hybridization and back-crosses. We have introgressed four translocations (EB4, IBj5, UK14-1, and B362i) from Neurospora crassa into N. tetrasperma. This enabled us to construct two general types of heterokaryons with mat-A and mat-a nuclei of different genotypes: one type is [T + N] (with one translocation nucleus and one normal sequence nucleus), and the other is [Dp + Df] (with one nucleus carrying a duplication of the translocation region and the other being deleted for the translocation region). Self-crossing these heterokaryons again produced [T + N] and [Dp + Df] progeny. From conidia (vegetative spores) produced by the heterokaryotic mycelia, we obtained self-fertile (heterokaryotic) and self-sterile (homokaryotic) derivative strains. [T + N] heterokaryons produced homokaryotic conidial derivatives of both mating types, but [Dp + Df] heterokaryons produced viable conidial homokaryons of only the mating type of the Dp nucleus. All four [T + N] heterokaryons and three [Dp + Df] heterokaryons produced both self-sterile and self-fertile conidial derivatives, but the [Dp(B362i) + Df(B362i)] heterokaryons produced only self-sterile ones. Conceivably, the Df(B362i) nuclei may be deleted for a nucleus-limited gene required for efficient mitosis or nuclear division, and whose deficit is not complemented by the neighboring Dp(B362i) nuclei. A cross involving Dp(EB4) showed repeat-induced point mutation (RIP). Because RIP can occur in self-crosses of [Dp + Df] but not [T + N] heterokaryons, RIP alteration of a translocated segment would depend on the relative numbers of [Dp + Df] vs. [T + N] ancestors.

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5 Small RNAs in Fungi

Nicolás

Murcia

Navarro

et al. 2020

Genetics and Biotechnology

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Meiotic silencing by unpaired DNA is expressed more strongly in the early than the late perithecia of crosses involving most wild-isolated Neurospora crassa strains and in self-crosses of N. tetrasperma

Cited by 18 publications

References 20 publications

TheNeurospora crassastandard Oak Ridge background exhibits an atypically efficient meiotic silencing by unpaired DNA

TheNeurospora crassastandard Oak Ridge background exhibits an atypically efficient meiotic silencing by unpaired DNA

Neurospora heterokaryons with complementary duplications and deficiencies in their constituent nuclei provide an approach to identify nucleus-limited genes

5 Small RNAs in Fungi

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