A moderately repetitive DNA sequence in alfalfa is transcribed in a floral-specific manner

Genome ◽  
1996 ◽  
Vol 39 (1) ◽  
pp. 9-16
Author(s):  
X. Xia ◽  
S. Du ◽  
L. Erickson
Keyword(s):  
Medicago Sativa ◽  
Dna Sequence ◽  
Repetitive Dna ◽  
Sequence Divergence ◽  
Coding Region ◽  
Flower Bud ◽  
Reading Frame ◽  
Sequence Homologies ◽  
Single Base Pair ◽  
Late Stages

Based on DNA sequence analysis of 5 clones of repetitive DNA from alfalfa (Medicago sativa), we propose the existence of a dispersed middle repetitive element about 3400 bp long with a copy number in the range of 2–3 × 103 per haploid genome. The average A + T content of the sequences was 54.6%, compared with 61.4% for the alfalfa genome. Sequence homologies between overlapping regions of the clones ranged from 85 to 89.5% with an average of 86.6%; sequence divergence was due largely to single base pair changes, with deletions or insertions occurring randomly across sequences. An open reading frame (ORF) in one clone, RPE15, contained homologies to cereal prolamin genes and a legumin box was located upstream of the coding region. A Northern blot of RNA from various alfalfa tissues, probed with the above clone containing this ORF, showed an extensive heterodispersed pattern of hybridization in the late stages of flower bud development but in no other tissues. Key words : lucerne, Medicago sativa, repetitive DNA, plant genomes.

Cloning and characterization of a highly repeated DNA sequence in Hordeum vulgare L.

Genome ◽  
1996 ◽  
Vol 39 (6) ◽  
pp. 1159-1168 ◽  
Author(s):  
Kebin Liu ◽  
Shauna Somerville
Keyword(s):  
Hordeum Vulgare ◽  
Reverse Transcriptase ◽  
Dna Sequence ◽  
Repetitive Dna ◽  
Sequence Divergence ◽  
Triticum Aestivum L ◽  
Reverse Transcriptase Gene ◽  
Hordeum Vulgare L ◽  
Reading Frame ◽  
Species Specific

A novel repetitive DNA sequence, R10hvcop, has been identified in the barley (Hordeum vulgare L.) genome. This 830 base pair (bp) DNA sequence has a 606-bp open reading frame and is present as approximately 1.96 × 105 copies per haploid barley genome. Southern blot analysis revealed that repetitive DNA elements containing R10hvcop and related sequences were dispersed within the barley chromosomes. Sequences similar to R10hvcop were also found in wheat (Triticum aestivum L.), rye (Secale cereale L.), and oat (Avena sativa L.) with copy numbers of 8 × 104, 1.39 × 105, and 7.9 × 104 per haploid genome, respectively. Sequences similar to R10hvcop were also present in the corn (Zea mays L. ssp. mays) genome, but they were not highly repeated. Barley, wheat, rye, oat, and corn showed species-specific restriction fragment length polymorphisms of R10hvcop and related sequences. Computer-based similarity searches revealed that R10hvcop is closely related to reverse transcriptase genes in retrotransposons and retrotransposon-like elements of several plant species and of Drosophila. The highly repetitive nature, interspersed distribution, and high degree of similarity to reverse transcriptase genes suggests that R10hvcop contains the sequence of a diverged reverse transcriptase gene. Key words : repetitive DNA, barley, reverse transcriptase gene, sequence divergence.

scholarly journals The Two Drosophila Telomeric Transposable Elements Have Very Different Patterns of Transcription

1999 ◽  
Vol 19 (1) ◽  
pp. 873-881 ◽  
Author(s):  
O. N. Danilevskaya ◽  
K. L. Traverse ◽  
N. C. Hogan ◽  
P. G. DeBaryshe ◽  
M. L. Pardue
Keyword(s):  
Transposable Elements ◽  
Sequence Similarity ◽  
Sequence Divergence ◽  
Full Length ◽  
Coding Region ◽  
Free Standing ◽  
Reading Frame ◽  
Sequence Organization ◽  
Sense Strand ◽  
Cell Fractions

ABSTRACT The transposable elements HeT-A and TARTconstitute the telomeres of Drosophila chromosomes. Both are non-long terminal repeat (LTR) retrotransposons, sharing the remarkable property of transposing only to chromosome ends. In addition, strong sequence similarity of their gag proteins indicates that these coding regions share a common ancestor. These findings led to the assumption that HeT-A andTART are closely related. However, we now find that these elements produce quite different sets of transcripts. HeT-Aproduces only sense-strand transcripts of the full-length element, whereas TART produces both sense and antisense full-length RNAs, with antisense transcripts in more than 10-fold excess over sense RNA. In addition, features of TART sequence organization resemble those of a subclass of non-LTR elements characterized by unequal terminal repeats. Thus, the ancestral gag sequence appears to have become incorporated in two different types of elements, possibly with different functions in the telomere. HeT-Atranscripts are found in both nuclear and cytoplasmic cell fractions, consistent with roles as both mRNA and transposition template. In contrast, both sense and antisense TART transcripts are almost entirely concentrated in nuclear fractions. Also,TART open reading frame 2 probes detect a cytoplasmic mRNA for reverse transcriptase (RT), with no similarity to TARTsequence 5′ or 3′ of the RT coding region. This RNA could be a processed TART transcript or the product of a “free-standing” RT gene. Either origin would be novel. The distinctive transcription patterns of both HeT-A andTART are conserved in Drosophila yakuba, despite significant sequence divergence. The conservation argues that these sets of transcripts are important to the function(s) ofHeT-A and TART.

An AT-rich satellite DNA sequence, E180, in alfalfa (Medicago sativa)

Genome ◽  
1993 ◽  
Vol 36 (3) ◽  
pp. 427-432 ◽  
Author(s):  
X. Xia ◽  
L. Erickson
Keyword(s):  
Medicago Sativa ◽  
Dna Sequence ◽  
Repetitive Dna ◽  
Dna Sequences ◽  
Satellite Dna ◽  
Nuclear Dna ◽  
Consensus Sequence ◽  
Repeated Dna Sequence ◽  
Dna Fragment ◽  
High Degree

A DNA fragment of ~750 bp was cloned from EcoRI-digested nuclear DNA of alfalfa (Medicago sativa). Southern blot and sequence analysis showed that the cloned DNA fragment represents a tetramer of a highly tandemly repeated DNA sequence of 185–188 bp (E180). The consensus sequence deduced from the four repeating units is 189 bp in length with an AT content of 67%. The copy number of the satellite DNA was estimated to be ~1.8 × 105 per genome and constitutes about 1% of the alfalfa genome. Sequence comparison revealed no identity to any repetitive DNA sequences that have been published to date. Digestion with HpaII and MspI indicated a high degree of methylation at the internal C of the restriction site CCGG within E180.Key words: alfalfa, Medicago, repetitive DNA sequence, satellite DNA.

scholarly journals Aspergillus nidulans wetA activates spore-specific gene expression.

1991 ◽  
Vol 11 (1) ◽  
pp. 55-62 ◽  
Author(s):  
M A Marshall ◽  
W E Timberlake
Keyword(s):  
Gene Expression ◽  
Cell Wall ◽  
Aspergillus Nidulans ◽  
Gene Activation ◽  
Regulatory Function ◽  
Specific Gene ◽  
Coding Region ◽  
Vegetative Cells ◽  
Mutant Strains ◽  
Late Stages

The Aspergillus nidulans wetA gene is required for synthesis of cell wall layers that make asexual spores (conidia) impermeable. In wetA mutant strains, conidia take up water and autolyze rather than undergoing the final stages of maturation. wetA is activated during conidiogenesis by sequential expression of the brlA and abaA regulatory genes. To determine whether wetA regulates expression of other sporulation-specific genes, its coding region was fused to a nutritionally regulated promoter that permits gene activation in vegetative cells (hyphae) under conditions that suppress conidiation. Expression of wetA in hyphae inhibited growth and caused excessive branching. It did not lead to activation of brlA or abaA but did cause accumulation of transcripts from genes that are normally expressed specifically during the late stages of conidiation and whose mRNAs are stored in mature spores. Thus, wetA directly or indirectly regulates expression of some spore-specific genes. At least one gene (wA), whose mRNA does not occur in spores but rather accumulates in the sporogenous phialide cells, was activated by wetA, suggesting that wetA may have a regulatory function in these cells as well as in spores. We propose that wetA is responsible for activating a set of genes whose products make up the final two conidial wall layers or direct their assembly and through this activity is responsible for acquisition of spore dormancy.

Promiscuos DNA: sequence homologies between DNA of separate organelles

1984 ◽  
Vol 9 (6) ◽  
pp. 271-273 ◽  
Author(s):  
Jeremy N. Timmis ◽  
N. Steele Scott
Keyword(s):  
Dna Sequence ◽  
Sequence Homologies

scholarly journals Two-dimensional graphic analysis of DNA sequence homologies

1982 ◽  
Vol 10 (1) ◽  
pp. 365-374 ◽  
Author(s):  
Robert Harr ◽  
Per Hagblom ◽  
Petter Gustafsso
Keyword(s):  
Dna Sequence ◽  
Two Dimensional ◽  
Graphic Analysis ◽  
Sequence Homologies

Sequence variation and evolution of nuclear DNA in man and the primates

1981 ◽  
Vol 292 (1057) ◽  
pp. 133-142 ◽  
Keyword(s):  
Dna Sequence ◽  
Sequence Variation ◽  
Nuclear Dna ◽  
Sequence Divergence ◽  
Gene Arrangement ◽  
Human Populations ◽  
Genetic Changes ◽  
Detailed Structural Analysis ◽  
Dna Sequence Variation ◽  
History Of

Recent advances in nucleic acid technology have facilitated the detection and detailed structural analysis of a wide variety of genes in higher organisms, including those in man. This in turn has opened the way to an examination of the evolution of structural genes and their surrounding and intervening sequences. In a study of the evolution of haemoglobin genes and neighbouring sequences in man and the primates, we have investigated gene arrangement and DNA sequence divergence both within and between species ranging from Old World monkeys to man. This analysis is beginning to reveal the evolutionary constraints that have acted on this region of the genome during primate evolution. Furthermore, DNA sequence variation, both within and between species, provides, in principle, a novel and powerful method for determining inter-specific phylogenetic distances and also for analysing the structure of present-day human populations. Application of this new branch of molecular biology to other areas of the human genome should prove important in unravelling the history of genetic changes that have occurred during the evolution of man.

scholarly journals Structural defects of a Pax8 mutant that give rise to congenital hypothyroidism

1999 ◽  
Vol 341 (1) ◽  
pp. 89-93 ◽  
Author(s):  
Gianluca TELL ◽  
Lucia PELLIZZARI ◽  
Gennaro ESPOSITO ◽  
Carlo PUCILLO ◽  
Paolo Emidio MACCHIA ◽  
...  
Keyword(s):  
Dna Sequence ◽  
Congenital Hypothyroidism ◽  
Dna Sequences ◽  
Dna Interaction ◽  
Structural Defects ◽  
Molecular Defect ◽  
Wild Type ◽  
Coding Region ◽  
Induced Fit ◽  
Helical Content

Pax proteins are transcriptional regulators that play important roles during embryogenesis. These proteins recognize specific DNA sequences via a conserved element: the paired domain (Prd domain). The low level of organized secondary structure, in the free state, is a general feature of Prd domains; however, these proteins undergo a dramatic gain in α-helical content upon interaction with DNA (‘induced fit’). Pax8 is expressed in the developing thyroid, kidney and several areas of the central nervous system. In humans, mutations of the Pax8 gene, which are mapped to the coding region of the Prd domain, give rise to congenital hypothyroidism. Here, we have investigated the molecular defects caused by a mutation in which leucine at position 62 is substituted for an arginine. Leu62 is conserved among Prd domains, and contributes towards the packing together of helices 1 and 3. The binding affinity of the Leu62Arg mutant for a specific DNA sequence (the C sequence of thyroglobulin promoter) is decreased 60-fold with respect to the wild-type Pax8 Prd domain. However, the affinities with which the wild-type and the mutant proteins bind to a non-specific DNA sequence are very similar. CD spectra demonstrate that, in the absence of DNA, both wild-type Pax8 and the Leu62Arg mutant possess a low α-helical content; however, in the Leu62Arg mutant, the gain in α-helical content upon interaction with DNA is greatly reduced with respect to the wild-type protein. Thus the molecular defect of the Leu62Arg mutant causes a reduced capability for induced fit upon DNA interaction.

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