scholarly journals Active Mutator elements suppress the knotted phenotype and increase recombination at the Kn1-O tandem duplication.

Genetics ◽  
1992 ◽  
Vol 132 (3) ◽  
pp. 813-822 ◽  
Author(s):  
B Lowe ◽  
J Mathern ◽  
S Hake
Keyword(s):  
Transposable Elements ◽  
Leaf Development ◽  
High Frequency ◽  
Homologous Chromosome ◽  
Tandem Duplication ◽  
Fold Increase ◽  
Transcription Unit ◽  
Mutant Phenotype ◽  
Maize Leaf ◽  
Specific Allele

Abstract The KNOTTED-1 (KN1) locus is defined by a number of dominant mutations that affect leaf development. The Kn1-O mutation is characterized by outpocketings of tissue along lateral veins of the maize leaf and by displacement of ligule tissue from the junction of the blade and sheath into the blade. Kn1-O results from a tandem duplication of 17 kb; each repeat includes the entire 8-kb KN1 transcription unit. Mutator (Mu) transposable elements inserted at the junction of the two repeats diminish the mutant phenotype. The Mu insertions affect the Kn1-O mutation in several distinctive ways. (1) Two of the three Mu elements, a Mu1 and a Mu8 element, diminish the mutant phenotype only when active as indicated by hypomethylation; when methylated or inactive, the phenotype is comparable to the Kn1-O progenitor. (2) Additional rearrangements have arisen in these derivatives that further reduce the mutant phenotype. (3) A 100-2000-fold increase in the loss of one repeat occurs in the presence of Mu elements as compared to Kn1-O without elements. The high frequency of loss only occurs when the Mu elements are hypomethylated. The frequency is also influenced by the specific allele carried at the same locus on the homologous chromosome. Reciprocal exchange of flanking markers does not accompany the loss events. Various recombination models that address the events occurring at Kn1-O are presented.

scholarly journals Distance and pairing effects on the brownDominant heterochromatic element in Drosophila.

Genetics ◽  
1995 ◽  
Vol 140 (3) ◽  
pp. 1007-1017 ◽  
Author(s):  
S Henikoff ◽  
J M Jackson ◽  
P B Talbert
Keyword(s):  
High Frequency ◽  
Homologous Chromosome ◽  
Tandem Duplication ◽  
Wild Type ◽  
X Ray ◽  
Cis Acting ◽  
Genetic Elements ◽  
Threshold Distance ◽  
Chromosome Arm

Abstract We examined the behavior of the brownDominant (bwD) heterochromatic insertion moved to different locations relative to centric heterochromatin. Effects were measured as the degree of silencing of a wild-type brown eye pigment gene by bwD across a tandem duplication. A series of X-ray-induced effects were recovered at high frequency. Cis-acting enhancers were obtained by relocation of the duplication closer to autosomal heterochromatin. Enhancers were also recovered on the homologous chromosome when it was similarly rearranged, revealing a novel interhomologue effect whereby interactions occur between genetic elements near opposite ends of a chromosome arm rather than between paired alleles. Cis-acting suppressors were obtained as secondary rearrangements in which the duplication was moved farther away from heterochromatin. Suppression was correlated with loss of cytological association between bwD and the polytene chromocenter. Surprisingly, the distance from bwD to the chromocenter was not correlated with the strength of enhancement or suppression. We propose that bwD fails to coalesce with the chromocenter when its position along the chromosome places it beyond a threshold distance from heterochromatin, and this threshold depends upon the configuration of both the chromosome carrying bwD and its paired homologue.

scholarly journals Mutator insertions in an intron of the maize knotted1 gene result in dominant suppressible mutations.

Genetics ◽  
1994 ◽  
Vol 138 (4) ◽  
pp. 1275-1285 ◽  
Author(s):  
B Greene ◽  
R Walko ◽  
S Hake
Keyword(s):  
Gene Expression ◽  
Transposable Elements ◽  
Leaf Development ◽  
Ectopic Expression ◽  
Mutant Phenotype ◽  
Northern Analysis

Abstract The knotted1 (kn1) locus of maize is defined by a series of dominant mutations affecting leaf development. We recovered 10 additional mutant alleles in lines containing active Mutator transposable elements. Nine of these alleles contain Mu1 or Mu8 elements inserted within a 310-bp region of the kn1 third intron. All five Mu8 insertions are in the same orientation whereas both orientations of Mu1 were recovered. Northern analysis showed that ectopic expression of kn1 within developing leaves is correlated with the mutant phenotype for the four alleles analyzed. Transcript size was not altered. The effect of Mu activity, as measured by the extent of Mu element methylation or by the presence of the autonomous MuDR element, was investigated for two alleles. Kn1-mum2, containing a Mu8 element, and Kn1-mum7, containing a Mu1 element, required Mu activity for the knotted phenotype. We examined the effect of Mu activity on ectopic kn1 expression in Kn1-mum2 and found that the transcript was present in leaves of Mu active individuals only. We discuss possible mechanisms by which Mu activity could condition kn1 gene expression.

scholarly journals A novel transvection phenomenon affecting the white gene of Drosophila melanogaster.

Genetics ◽  
1990 ◽  
Vol 126 (1) ◽  
pp. 167-176
Author(s):  
D Gubb ◽  
M Ashburner ◽  
J Roote ◽  
T Davis
Keyword(s):  
Drosophila Melanogaster ◽  
Homologous Chromosome ◽  
Tandem Duplication ◽  
Gamma Ray ◽  
Insertion Site ◽  
Hairpin Loop ◽  
Homologous Chromosomes ◽  
Inverted Order ◽  
In Trans ◽  
In Cis

Abstract The zeste mutation of Drosophila melanogaster suppresses the expression of white genes in the eye. This suppression is normally dependent on there being two copies of w+ located close to each other in the genome--they may either be in cis (as in a tandem duplication of w+) or in trans, i.e. on homologous chromosomes. Duplicated w+ genes carried by a giant transposing element, TE146(Z), are suppressed by z whether they are in direct (tandem) or inverted order. The tandem form of the TE is very sensitive to a rearrangement on the homologous chromosome--many rearrangements with breakpoints "opposite" the TE's insertion site prevent the interaction between the white genes on a z background. These aberrations act as dominant suppressors of zeste that are specific to the tandemly duplicated form of TE146(Z). The inverted form of the TE146(Z) presumably pairs as a hairpin loop; this is more stable than the tandem form by the criterion that its zeste phenotype is unaffected by any of the aberrations. This effect of rearrangements has been used as the basis for a screen, gamma-ray induced aberrations with at least one breakpoint opposite the TE site were recovered by their suppression of the zeste phenotype.

Probing Drosophila gene function by antisense RNA

Genome ◽  
1989 ◽  
Vol 31 (1) ◽  
pp. 422-425 ◽  
Author(s):  
Reinhard Schuh ◽  
Herbert Jäckle
Keyword(s):  
Antisense Rna ◽  
Germ Line ◽  
Conventional Technique ◽  
Transcription Unit ◽  
The Body ◽  
Mutant Phenotype ◽  
Drosophila Embryo ◽  
Alternative Approach ◽  
Pattern Forming ◽  
Germ Line Transformation

The conventional technique for assigning a particular genetic function to a cloned transcription unit has relied on the rescue of the mutant phenotype by germ line transformation. An alternative approach is to mimic a mutant phenotype by the use of antisense RNA injections to produce phenocopies. This approach has been successfully used to identify genes involved in early pattern forming processes in the Drosophila embryo. At the time when antisense RNA is injected, the embryo develops as a syncytium composed of about 5000 nuclei which share a common cytoplasm. The gene interactions required to establish the body plan occur before cellularization at the blastoderm stage. Thus the nuclei and their exported transcripts are accessible to the injected antisense RNA. The antisense RNA interferes with the endogenous RNA by an as yet unidentified mechanism. The extent of interference is only partial and produces phenocopies with characteristics of weak mutant alleles. In our lab and others, this approach has been successfully used to identify several genes required for normal Drosophila pattern formation.Key words: Drosophila segmentation, phenocopy, antisense RNA, Krüppel gene.

Comparison of intron-dependent and intron-independent gene expression

1988 ◽  
Vol 8 (10) ◽  
pp. 4395-4405
Author(s):  
A R Buchman ◽  
P Berg
Keyword(s):  
Simian Virus 40 ◽  
Plasmid Vector ◽  
Fold Increase ◽  
Simian Virus ◽  
Transcription Unit ◽  
Vector System ◽  
Beta Globin ◽  
Animal Cells ◽  
Transcriptional Enhancer ◽  
Kinase Gene

Recombinant simian virus 40 viruses carrying rabbit beta-globin cDNA failed to express the beta-globin sequence unless an intron was included in the transcription unit. The addition of either beta-globin IVS1 or IVS2 caused a 400-fold increase in RNA production. Stable beta-globin RNA production required sequences in IVS2 that were very close to the splice sites and that coincided with those needed for mRNA splicing. In addition to the recombinant viruses, intron-dependent expression was observed with both replicating and nonreplicating plasmid vectors in short-term transfections of cultured animal cells. Unlike transcriptional enhancer elements, IVS2 failed to increase stable RNA production when it was placed downstream of the polyadenylation site. Using a plasmid vector system to survey different inserted sequences for their dependence on introns for expression, we found that the presence of IVS2 stimulated the expression of these sequences 2- to 500-fold. Sequences from the transcribed region of the herpes simplex virus thymidine kinase gene, a gene that lacks an intervening sequence, permitted substantial intron-independent expression (greater than 100-fold increase) in the plasmid vector system.

Sequence Organization and Conservation in sh2/a1-Homologous Regions of Sorghum and Rice

Genetics ◽  
1998 ◽  
Vol 148 (1) ◽  
pp. 435-443
Author(s):  
Mingsheng Chen ◽  
Phillip SanMiguel ◽  
Jeffrey L Bennetzen
Keyword(s):  
Transposable Elements ◽  
Long Terminal Repeat ◽  
Inverted Repeat ◽  
Tandem Duplication ◽  
Regulatory Gene ◽  
Terminal Repeat ◽  
Homologous Segment ◽  
Sequence Organization ◽  
Transcriptional Regulatory ◽  
Evolutionarily Conserved

Abstract Previously, we have demonstrated microcolinearity of gene composition and orientation in sh2/a1-homologous regions of the rice, sorghum, and maize genomes. However, the sh2 and a1 homologues are only about 20 kb apart in both rice and sorghum, while they are separated by about 140 kb in maize. In order to further define sequence organization and conservation in sh2/a1-homologous regions, we have completely sequenced a 42,446-bp segment of sorghum DNA. Four genes were identified: a homologue of sh2, two homologues of a1, and a putative transcriptional regulatory gene. A solo long terminal repeat of the retroelement Leviathan was detected between the two a1 homologues, and eight miniature inverted repeat transposable elements were found in this region. Comparison of the sorghum sequence with the sequence of the homologous segment from rice indicated that only the identified genes were evolutionarily conserved between these two species, which have evolved independently for over 50 million years. The introns of the a1 homologues have evolved faster than the introns of the sh2 homologue. The a1 tandem duplication appears to be an ancient event that may have preceded the ancestral divergence of maize, sorghum, and rice.

scholarly journals Parallel Proteomic and Phosphoproteomic Analyses of Successive Stages of Maize Leaf Development

2013 ◽  
Vol 25 (8) ◽  
pp. 2798-2812 ◽  
Author(s):  
Michelle R. Facette ◽  
Zhouxin Shen ◽  
Fjola R. Björnsdóttir ◽  
Steven P. Briggs ◽  
Laurie G. Smith
Keyword(s):  
Leaf Development ◽  
Maize Leaf

Follicle size and reproductive hormone profiles during a post-weaning altrenogest treatment in primiparous sows

2015 ◽  
Vol 27 (2) ◽  
pp. 304 ◽  
Author(s):  
J. J. J. van Leeuwen ◽  
M. R. T. M. Martens ◽  
J. Jourquin ◽  
M. A. Driancourt ◽  
A. Wagner ◽  
...  
Keyword(s):  
High Frequency ◽  
Fold Increase ◽  
High Amplitude ◽  
Daily Administration ◽  
Reproductive Hormone ◽  
Diurnal Pattern ◽  
Once Daily ◽  
Follicular Wave ◽  
Follicle Size ◽  
Low Amplitude

This study investigated the endocrine background of follicle size changes during post-weaning altrenogest treatment. altrenogest-treated sows received a 20-mg dosage daily at 8.00 a.m. from Day –1 to Day 14 after weaning. On Day –1, only 3/13 altrenogest-treated sows showed LH pulses compared with 8/8 control sows (P = 0.001). On Day 0, control sows showed a typical high frequency–low amplitude LH pattern, indicative for recruitment of oestrogenic follicles. In altrenogest-treated animals on Day 0, half of the sows showed high frequency–high amplitude pulses from 4–5 h after weaning. In altrenogest-treated sows, average follicle size increased from 3.1 ± 0.5 mm on Day 0 to 4.4 ± 0.6 mm on Day 5, then decreased to 3.7 ± 0.5 mm on Day 7 and stabilised thereafter. FSH and oestradiol (E2) concentrations showed a distinct diurnal pattern; high at 7.00 a.m. and low at 3.00 p.m. E2 concentrations (7.00 a.m.) showed a 2.5-fold increase from Day –1 to Day 2, and subsequently a 2-fold decline to reach a plateau at Day 8. FSH concentrations reached maximum levels by Day 5 and slowly declined afterwards. In conclusion, once-daily administration of altrenogest starting one day before weaning delays the weaning-induced increase in LH pulses. Although FSH and follicle size increase until Day 5 after weaning, follicle E2 production already decreased from Day 2 after weaning. Post-weaning altrenogest treatment thus results in a follicular wave of follicles that lose oestrogenic competence at Day 2 after weaning, presumably related to the changed LH dynamics during altrenogest treatment.

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