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1.
J Gen Virol ; 78 ( Pt 5): 1165-74, 1997 May.
Article in English | MEDLINE | ID: mdl-9152437

ABSTRACT

The complete sequence of a Tennessee isolate of maize chlorotic dwarf virus (MCDV-TN) was determined from cDNA clones and by direct sequencing of the viral RNA. The genome is 11813 nucleotides (nt) in length and contains one large open reading frame between nt 435 and 10763 that encodes a polyprotein of 3443 amino acids. The N-terminal amino acid sequences were determined for the three capsid proteins. All three were adjacent, starting at nt 2526 and putatively ending at nt 3761. Comparison of the sequence of MCDV-TN with other viral sequences revealed similarities to several plant picorna-like viruses including members of the Sequiviridae, Comoviridae and Potyviridae. This work also provides evidence based on genome organization that MCDV-TN is a member of the genus Waikavirus within the family Sequiviridae.


Subject(s)
Plant Viruses/genetics , RNA Viruses/genetics , Amino Acid Sequence , Base Sequence , Capsid/metabolism , Conserved Sequence , Genome, Viral , Molecular Sequence Data , Plant Viruses/classification , Protein Processing, Post-Translational , Proteins/metabolism , RNA Viruses/classification , RNA, Viral , Sequence Analysis, RNA , Zea mays/virology
2.
Proc Natl Acad Sci U S A ; 91(25): 11792-6, 1994 Dec 06.
Article in English | MEDLINE | ID: mdl-7991537

ABSTRACT

The wx-K mutation results from the insertion of a copia-like retrotransposon into exon 12 of the maize waxy gene. This retrotransposon, named Hopscotch, has one long open reading frame encoding all of the domains required for transposition. Computer-assisted database searches using Hopscotch and other plant copia-like retroelements as query sequences have revealed that ancient, degenerate retrotransposon insertions are found in close proximity to 21 previously sequenced plant genes. The data suggest that these elements may be involved in gene duplication and the regulation of gene expression. Similar searches using the Drosophila retrotransposon copia did not reveal any retrotransposon-like sequences in the flanking regions of animal genes. These results, together with the recent finding that reverse-transcriptase sequences characteristic of copia-like elements are ubiquitous and diverse in plants, suggest that copia-like retrotransposons are an ancient component of plant genomes.


Subject(s)
Biological Evolution , Gene Expression , Genes, Plant , Retroelements , Zea mays/genetics , Amino Acid Sequence , Animals , Cloning, Molecular , Conserved Sequence , DNA Transposable Elements , DNA, Plant/genetics , DNA, Plant/isolation & purification , Drosophila/genetics , Molecular Sequence Data , Sequence Homology, Amino Acid , Species Specificity
3.
Arch Virol ; 138(1-2): 27-38, 1994.
Article in English | MEDLINE | ID: mdl-7980009

ABSTRACT

The 3'-terminal 1902 nucleotides of the tobacco vein-banding mosaic virus (TVBMV) were cloned and sequenced. The sequence contains a large open reading frame of 572 amino acid residues followed by a non-coding region of 183 nucleotides which terminates in a polyadenylate tract. The TVBMV coat protein is processed from a larger polyprotein by cleavage at a Gln/Gly dipeptide, which is followed closely by the aphid transmission DAG triplet. Translation of the nucleotide sequence yielded a protein of 271 amino acid residues with a calculated M(r) of 30,347. The amino acid and nucleotide sequences of the TVBMV coat protein and 3' non-coding region were compared to 33-35 other virus sequences. Percent sequence identity of the amino acid and nucleotide sequences were in the range expected from comparison of distinct viruses. Phylogenetic analyses were also performed to determine the relationship of TVBMV to other well-characterized viruses. These studies indicate that TVBMV should be regarded as a distinct member of the potyvirus group.


Subject(s)
Capsid/genetics , Genome, Viral , Potyvirus/genetics , Amino Acid Sequence , Cloning, Molecular , DNA, Viral , Molecular Sequence Data , Plants, Toxic , Nicotiana/virology
4.
Genetics ; 132(2): 529-44, 1992 Oct.
Article in English | MEDLINE | ID: mdl-1330825

ABSTRACT

In Drosophila melanogaster males, X-Y meiotic chromosome pairing is mediated by the nucleolus organizers (NOs) which are located in the X heterochromatin (Xh) and near the Y centromere. Deficiencies for Xh disrupt X-Y meiotic pairing and cause high frequencies of X-Y nondisjunction. Insertion of cloned rRNA genes on an Xh- chromosome partially restores normal X-Y pairing and disjunction. To map the sequences within an inserted, X-linked rRNA gene responsible for stimulating X-Y pairing, partial deletions were generated by P element-mediated destabilization of the insert. Complete deletions of the rRNA transcription unit did not interfere with the ability to stimulate X-Y pairing as long as most of the intergenic spacer (IGS) remained. Within groups of deletions that lacked the entire transcription unit and differed only in length of residual IGS material, pairing ability was proportional to the dose of 240-bp intergenic spacer repeats. Deletions of the complete rRNA transcription unit or the 28S sequences alone blocked nucleolus formation, as determined by binding of an antinucleolar antibody, yet did not interfere with pairing ability, suggesting that X-Y pairing may not be mechanistically related to nucleolus formation. A model for achiasmatic pairing in Drosophila males based upon the combined action of topoisomerase I and a strand transferase is proposed.


Subject(s)
Drosophila melanogaster/genetics , Meiosis/genetics , RNA, Transfer/genetics , Repetitive Sequences, Nucleic Acid , Animals , Base Sequence , Cell Nucleolus/ultrastructure , DNA Transposable Elements , DNA, Ribosomal/genetics , Gene Deletion , Introns , Male , Models, Genetic , Molecular Sequence Data , Mutagenesis, Site-Directed , Phenotype , X Chromosome , Y Chromosome
5.
Dev Genet ; 13(6): 468-84, 1992.
Article in English | MEDLINE | ID: mdl-1304425

ABSTRACT

The Drosophila melanogaster ribosomal DNA (rDNA) functions as an X-Y meiotic pairing site. Deletions encompassing the X chromosomal rDNA block (located in the heterochromatin) disrupt X-Y pairing and disjunction. Insertions of single, complete rRNA genes at ectopic locations on the heterochromatically deficient X partially restore X-Y pairing capacity. This study was undertaken to test fragments of an rDNA repeat for the ability to stimulate X-Y pairing and disjunction and to test for relationships between pairing capacity and two other phenotypes associated with rDNA insertions: transcription and the ability to organize a nucleolus. Insertions of three different fragments, all of which retained the rDNA promoter and upstream spacer sequences and which differed among each other in the length of downstream sequences, were obtained by P-element mediated transformation. One of the fragments is truncated only 140bp downstream from the promoter. Insertions of all three fragments proved capable of stimulating X-Y disjunction. Double insertions were substantially more effective than single insertions. RNA/PCR analysis was used to show that transcripts initiated at the inserted rDNA promoters are present in testis RNA from all insertions. Treatment with an antinucleolar antibody revealed that none of the insertions was associated with a mininucleolus. Thus promoter-containing rDNA fragments are autonomously capable of being transcribed and of functioning as X-Y pairing sites, but not of forming a mini-nucleolus.


Subject(s)
Drosophila melanogaster/genetics , Meiosis/genetics , Animals , Animals, Genetically Modified , Base Sequence , DNA, Ribosomal , Male , Molecular Sequence Data , Polymerase Chain Reaction , Promoter Regions, Genetic , Restriction Mapping , X Chromosome , Y Chromosome
6.
Proc Natl Acad Sci U S A ; 86(18): 7092-6, 1989 Sep.
Article in English | MEDLINE | ID: mdl-2674946

ABSTRACT

Previous studies have suggested that the R locus of maize is responsible for determining the temporal and spatial pattern of anthocyanin pigmentation in the plant. In this report we demonstrate that three members of the R gene family, P, S, and Lc, encode homologous transcripts 2.5 kilobases in length. The structure of one R gene, Lc, was determined by sequencing cDNA and genomic clones. The putative Lc protein, deduced from the cDNA sequence, is composed of 610 amino acids and has homology to the helix-loop-helix DNA-binding/dimerization motif found in the L-myc gene product and other regulatory proteins. It also contains a large acidic domain that may be involved in transcriptional activation. Consistent with its proposed role as a transcriptional activator is our finding that a functional R gene is required for the accumulation of transcripts of at least two genes in the anthocyanin biosynthetic pathway. We discuss the possibility that the diverse patterns of anthocyanin pigmentation conditioned by different R genes reflect differences in the R gene promoters rather than their gene products.


Subject(s)
Anthocyanins/genetics , Genes , Multigene Family , Plant Proteins/genetics , Plants/genetics , Proto-Oncogene Proteins/genetics , Proto-Oncogenes , Amino Acid Sequence , Base Sequence , Blotting, Northern , Cloning, Molecular , DNA/genetics , Molecular Sequence Data , Proto-Oncogene Proteins c-myc , Sequence Homology, Nucleic Acid , Zea mays/genetics
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