scholarly journals Ds-INDUCED ALLELES AT THE OPAQUE-2 LOCUS OF MAIZE

Genetics ◽  
1986 ◽  
Vol 112 (1) ◽  
pp. 121-133
Author(s):  
Mario Motto ◽  
Renzo Marotta ◽  
Natale Di Fonzo ◽  
Carlo Soave ◽  
Francesco Salamini
Keyword(s):  
Transposable Elements ◽  
Transposon Mutagenesis ◽  
Dna Fragments ◽  
Wild Type ◽  
Genetic Analyses ◽  
Somatic Instability ◽  
Mutable Allele ◽  
Recessive Phenotype ◽  
Maize Plants ◽  
Ds Element

ABSTRACT Transposon mutagenesis has been used to isolate mutable alleles at the Opaque-2 (O2) locus of maize. Plants with the Activator-Dissociation (Ac-Ds) system of transposable elements and O2 were crossed as males to a stable o2 tester line. Among a population of 200,000 kernels, 198 exceptional kernels with somatic instability were recovered. In four cases, designated O2-m1, o2-m2, O2-m3 and O2-m4, variegated phenotypes appeared in F2 and subsequent generations. Genetic analyses indicated that the presence of Ds near or within the O2 gene was responsible for the observed somatic instability at the O2 locus. The phenotypes of the newly induced alleles were of two types. Alleles O2-m1, O2-m3 and O2-m4, in the absence of Ac, were characterized by kernel phenotypes indistinguishable from the wild type; in the presence of Ac they generated kernels with opaque sectors interspersed within a vitreous background. In contrast, the mutable allele o2-m2, in the absence of Ac, was characterized by kernels with a recessive phenotype similar to o2 recessive mutants. In the presence of Ac, it reverted somatically to wild-type-producing kernels with vitreous spots in an o2 background. The association of the Ds element with the O2 locus may prove a valuable tool directed to the isolation of DNA fragments bearing the O2 gene.

scholarly journals The molecular basis of instability of the singedvery weak mutation in Drosophila melanogaster

1994 ◽  
Vol 63 (1) ◽  
pp. 19-26 ◽  
Author(s):  
C. A. Ortori ◽  
D. Chambers ◽  
J. F. Y. Brookfield
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Elements ◽  
Maternal Effect ◽  
Molecular Basis ◽  
Germ Line ◽  
Pcr Amplification ◽  
Wild Type ◽  
High Frequencies ◽  
Somatic Instability ◽  
Sequential Addition

SummaryThe singedvery weak mutation was created by the sequential addition of two P transposable elements to the singed gene. The mutation can be somatically unstable through the action of a dominant maternal effect mutation on the second chromosome. It is also unstable in the germ line in these conditions. Sequencing of the region of the P insertions in the mutation reveals that the two inserted elements have single internal deletions, and the larger of the two is a copy of the KP element. The mutation will generate, at high frequencies, strongly singed and pseudo-wild type products by reversions occurred in the germline. These are the result of the precise excision of the smaller and the larger elements respectively. By PCR amplification of dissected thoraces we show that the somatic instability of the mutation, from a weak to a strong singed phenotype, is also caused by the excision of the smaller of the two elements.

scholarly journals Isolation of omnipotent suppressors in an [eta+] yeast strain.

Genetics ◽  
1990 ◽  
Vol 124 (3) ◽  
pp. 505-514 ◽  
Author(s):  
J A All-Robyn ◽  
D Kelley-Geraghty ◽  
E Griffin ◽  
N Brown ◽  
S W Liebman
Keyword(s):  
Yeast Strain ◽  
Guanidine Hydrochloride ◽  
Wild Type ◽  
Translational Fidelity ◽  
Genetic Analyses ◽  
Mendelian Factor ◽  
Nonsense Codons

Abstract Omnipotent suppressors decrease translational fidelity and cause misreading of nonsense codons. In the presence of the non-Mendelian factor [eta+], some alleles of previously isolated omnipotent suppressors are lethal. Thus the current search was conducted in an [eta+] strain in an effort to identify new suppressor loci. A new omnipotent suppressor, SUP39, and alleles of sup35, sup45, SUP44 and SUP46 were identified. Efficiencies of the dominant suppressors were dramatically reduced in strains that were cured of non-Mendelian factors by growth on guanidine hydrochloride. Wild-type alleles of SUP44 and SUP46 were cloned and these clones were used to facilitate the genetic analyses. SUP44 was shown to be on chromosome VII linked to cyh2, and SUP46 was clearly identified as distinct from the linked sup45.

Effects of mutation position on frequency of marker rescue by homologous recombination

1992 ◽  
Vol 12 (8) ◽  
pp. 3609-3613
Author(s):  
L Jiang ◽  
A Connor ◽  
M J Shulman
Keyword(s):  
Homologous Recombination ◽  
Normal Function ◽  
Constant Region ◽  
Dna Fragments ◽  
Wild Type ◽  
End Effect ◽  
Chromosomal Dna ◽  
Base Pairs ◽  
Marker Rescue ◽  
Immunoglobulin Mu

Homologous recombination between transferred and chromosomal DNA can be used for mapping mutations by marker rescue, i.e., by identifying which segment of wild-type DNA can recombine with the mutant chromosomal gene and restore normal function. In order to define how much the fragments should overlap each other for reliable mapping, we have measured how the frequency of marker rescue is affected by the position of the chromosomal mutation relative to the ends of the transferred DNA fragments. For this purpose, we used several DNA fragments to effect marker rescue in two mutant hybridomas which bear mutations 673 bp apart in the exons encoding the second and third constant region domains of the immunoglobulin mu heavy chain. The frequency of marker rescue decreased greatly when the mutation was located near one of the ends of the fragments, the results indicating that fragments should be designed to overlap by at least several hundred base pairs. Possible explanations for this "end effect" are considered.

Rice Functional Genomics by Transposon Mutagenesis

2002 ◽  
Vol 06 (24) ◽  
pp. 930-935 ◽  
Author(s):  
Chang-deok Han
Keyword(s):  
Tissue Culture ◽  
Transposable Elements ◽  
Functional Genomics ◽  
Large Scale ◽  
Expression Patterns ◽  
Transposon Mutagenesis ◽  
Transposon Tagging ◽  
Genomic Sequences ◽  
Knock Out ◽  
Genetic Cross

Transposable elements are powerful mutagens. Along with genomic sequences, knock-out phenotypes and expression patterns are important information to elucidate the function of genes. In this review, I propose a strategy to develop tranposant lines on a large scale by combining genetic cross and tissue culture of Ac and Ds lines. Based on the facts that Ds tends to be inactive in F2 or later generation and Ds becomes reactivated via tissue culture, a large scale of transposants can be produced by tissue culture of seeds carrying Ac and inactive Ds. In this review, I describe limitations and considerations in operating transposon tagging systems in rice. Also, I discuss the efficiency of our gene trap system and technical procedures to clone Ds flanking DNA.

scholarly journals A nucleosome positioned in the distal promoter region activates transcription of the human U6 gene.

1997 ◽  
Vol 17 (8) ◽  
pp. 4397-4405 ◽  
Author(s):  
W Stünkel ◽  
I Kober ◽  
K H Seifart
Keyword(s):  
Micrococcal Nuclease ◽  
Deletion Mutants ◽  
Dna Fragments ◽  
Wild Type ◽  
Sequence Element ◽  
Proximal Sequence Element ◽  
Experimental Approaches ◽  
Type Gene ◽  
Distal Promoter ◽  
U6 Gene

To investigate the consequences of chromatin reconstitution for transcription of the human U6 gene, we assembled nucleosomes on both plasmids and linear DNA fragments containing the U6 gene. Initial experiments with DNA fragments revealed that U6 sequences located between the distal sequence element (DSE) and the proximal sequence element (PSE) lead to the positioning of a nucleosome partially encompassing these promoter elements. Furthermore, indirect end-labelling analyses of the reconstituted U6 wild-type plasmids showed strong micrococcal nuclease cuts near the DSE and PSE, indicating that a nucleosome is located between these elements. To investigate the influence that nucleosomes exert on U6 transcription, we used two different experimental approaches for chromatin reconstitution, both of which resulted in the observation that transcription of the U6 wild-type gene was enhanced after chromatin assembly. To ensure that the facilitated transcription of the nucleosomal templates is in fact due to a positioned nucleosome, we constructed mutants of the U6 gene in which the sequences between the DSE and PSE were progressively deleted. In contrast to what was observed with the wild-type genes, transcription of these deletion mutants was significantly inhibited when they were packaged into nucleosomes.

Plasma cell-free DNA and fraction of circulating KRAS mutations as prognostic in patients with metastatic colorectal cancer.

2014 ◽  
Vol 32 (3_suppl) ◽  
pp. 490-490 ◽  
Author(s):  
David Sefrioui ◽  
Nasrin Vasseur ◽  
Richard Sesboüé ◽  
France Blanchard ◽  
Alice Oden-Gangloff ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Metastatic Colorectal Cancer ◽  
Plasma Cell ◽  
Circulating Tumor Dna ◽  
Dna Fragments ◽  
Wild Type ◽  
Kras Mutations ◽  
Cell Free Dna ◽  
Free Dna ◽  
Tumor Dna

490 Background: It has been suggested that detection of circulating tumor DNA may be relevant in patients with metastatic colorectal cancer (mCRC). The main objective of the present study was to evaluate a method based on the TaqMan Mutation Detection Assay (TMDA) for the detection of circulating KRAS mutations in mCRC patients. Moreover, we also investigated the prognostic impact of the plasma cell-free DNA and the fraction of circulating KRAS mutations. Methods: The study was conducted from April to July 2013 and plasma samples were prospectively collected in a series of 35 mCRC patients treated with chemotherapy (CT). QIAamp Circulating Nucleic Acid kit was used for DNA extraction and Quant-iT High Sensitivity dsDNA Assay for cf-DNA quantification. Detection of circulating tumor DNA was based on the KRAS mutations detected in tumour and was performed in plasma by the castPCR Technology TMDA. Response to CT was assessed according to RECIST criteria. The results of plasma cf-DNA and level of mutant DNA fragments were correlated with response and 3-months survival. Results: We isolated and quantified plasma cf-DNA in all patients with a mean concentration of 106 ng/mL. Among them, 18 were wild-type and 17 mutated for KRAS in the tumour. Detection of circulating KRAS mutations was performed with TMDA in 23 patients (10 KRAS wild-type and 13 KRAS mutated). The sensitivity was 62% (8/13) and specificity 100% (0/10) with a level of circulating mutant DNA fragments ranging from 0 to 29%. Plasma cf-DNA and level of circulating mutant DNA were both significantly correlated with the 3-months survival (mean 36 versus 524 ng/mL, p=0.0015 and 2% versus 29%, p<0.0001). There was a non significant trend for response to CT (respectively p=0.14 and p=0.12). Conclusions: TMDA method is a simple, accurate and non-invasive tool for the detection of circulating tumor DNA. Our preliminary results also suggest that plasma cf-DNA and fraction of mutant DNA fragments could be prognostic markers in mCRC patients.

scholarly journals CONTROL OF ANTHOCYANIN SYNTHESIS IN PETUNIA HYBRIDA BY MULTIPLE ALLELIC SERIES OF THE GENES An1 AND An2

Genetics ◽  
1984 ◽  
Vol 106 (3) ◽  
pp. 501-508
Author(s):  
Anton G M Gerats ◽  
Eliane Farcy ◽  
Marco Wallroth ◽  
Steven P C Groot ◽  
André Schram
Keyword(s):  
Petunia Hybrida ◽  
Anthocyanin Synthesis ◽  
Continuous Series ◽  
Wild Type ◽  
Allelic Series ◽  
Multiple Series ◽  
Anthocyanin Concentration ◽  
Mutable Allele ◽  
Multiple Allelic Series ◽  
Composition Changes

ABSTRACT A mutable allele of the An1 locus in Petunia hybrida has given rise to a multiple series of stable derivative alleles. Anthocyanin concentration in mature flowers of these mutants (an1  +/p/an1) decreases from the wild-type red to the recessive white in a continuous series. Anthocyanin composition changes regularly: the ratio of peonidin to cyanidin is 3.5 for an an1  +/+/an1 and 1.2 for an an1  +/p5/an1 mutant. Analysis of anthocyanins during flower development indicates that these differences in composition are due to the specific state of the An1 locus and not to anthocyanin concentration. Anthocyanin concentration in flowers of the allelic series for An1 correlates with the activity of the enzymes UDP-glucose: flavonoid-3-O-glucosyltransferase and SAM: anthocyanin-3′-O-methyltransferase. The same correlations were found for members of a comparable allelic series at the An2 locus. The possibility that the correlation between the enzyme activities is due to the occurrence of a multienzyme complex is discussed.

scholarly journals RNA-directed DNA methylation prevents rapid and heritable reversal of transposon silencing under heat stress in Zea mays

PLoS Genetics ◽  
2021 ◽  
Vol 17 (6) ◽  
pp. e1009326
Author(s):  
Wei Guo ◽  
Dafang Wang ◽  
Damon Lisch
Keyword(s):  
Dna Methylation ◽  
Transposable Elements ◽  
Histone H3 ◽  
Transcriptional Silencing ◽  
Epigenetic Silencing ◽  
Terminal Inverted Repeat ◽  
Wild Type ◽  
Rna Dependent Rna Polymerase ◽  
Plant Genomes ◽  
Transposon Silencing

In large complex plant genomes, RNA-directed DNA methylation (RdDM) ensures that epigenetic silencing is maintained at the boundary between genes and flanking transposable elements. In maize, RdDM is dependent on Mediator of Paramutation 1 (Mop1), a putative RNA dependent RNA polymerase. Here we show that although RdDM is essential for the maintenance of DNA methylation of a silenced MuDR transposon in maize, a loss of that methylation does not result in a restoration of activity. Instead, heritable maintenance of silencing is maintained by histone modifications. At one terminal inverted repeat (TIR) of this element, heritable silencing is mediated via histone H3 lysine 9 dimethylation (H3K9me2), and histone H3 lysine27 dimethylation (H3K27me2), even in the absence of DNA methylation. At the second TIR, heritable silencing is mediated by histone H3 lysine 27 trimethylation (H3K27me3), a mark normally associated with somatically inherited gene silencing. We find that a brief exposure of high temperature in a mop1 mutant rapidly reverses both of these modifications in conjunction with a loss of transcriptional silencing. These reversals are heritable, even in mop1 wild-type progeny in which methylation is restored at both TIRs. These observations suggest that DNA methylation is neither necessary to maintain silencing, nor is it sufficient to initiate silencing once has been reversed. However, given that heritable reactivation only occurs in a mop1 mutant background, these observations suggest that DNA methylation is required to buffer the effects of environmental stress on transposable elements.

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