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E H Davidson

Publications and source records attributed to E H Davidson.

At least 163 records · Page 9Linked to original sources
PubMed1983

Transcripts of three mitochondrial genes in the RNA of sea urchin eggs and embryos.

cDNA clones representing mitochondrial 16 S rRNA, and mRNAs for cytochrome oxidase I and an unidentified reading frame were used to measure the prevalence and stability of these transcripts in gastrula stage embryos. The 16 S rRNA is the most prevalent embryo poly(A) RNA, and is synthesized about four times more rapidly than is the mRNA for cytochrome oxidase. The relative prevalence of the two mRNAs is largely determined by their turnover rates.

Animals↗
PubMed1983

Comparison of sea urchin and human mtDNA: evolutionary rearrangement.

Clones of full-length mtDNA have been isolated from a Strongylocentrotus franciscanus recombinant DNA library by screening a cDNA clone of cytochrome oxidase subunit 1 mRNA. Restriction fragment cross-hybridization analysis shows the following difference in gene arrangement between sea urchin and human mtDNA. The 16S rRNA and cytochrome oxidase subunit 1 genes are directly adjacent in sea urchin mtDNA. These two genes are separated in human and other mammalian mtDNAs by the region containing unidentified reading frames 1 and 2. In spite of the difference in gene order, gene polarity appears to have been conserved. We conclude that the difference in gene order reflects a rearrangement that took place in the sea urchin lineage since sea urchins and mammals last shared a common ancestor.

Animals↗
PubMed1982

Molecular biology of the sea urchin embryo.

Research on the early development of the sea urchin offers new insights into the process of embryogenesis. Maternal messenger RNA stored in the unfertilized egg supports most of the protein synthesis in the early embryo, but the structure of maternal transcripts suggests that additional functions are also possible. The overall developmental patterns of transcription and protein synthesis are known, and current measurements describe the expression of specific genes, including the histone genes, the ribosomal genes, and the actin genes. Possible mechanisms of developmental commitment are explored for regions of the early embryo that give rise to specified cell lineages, such as the micromere-mesenchyme cell lineage.

Actins↗
PubMed1981

Molecular structure of maternal RNA.

The presence of a stable maternal mRNA population in mature oocytes of many species is well established. In this paper we show that the mature egg contains, in addition to these mature mRNAs, a structurally more complex population of RNA transcripts. This latter class of RNA consists of polyadenylated transcripts of repetitive and nonrepetitive DNA elements covalently linked into long interspersed molecules. As much as seventy percent of the polyadenylated egg RNA of Xenopus laevis and Strongylocentrotus purpuratus is represented in this interspersed population. Most of the nonrepetitive DNA sequences represented in the mature mRNA population are also present in the interspersed RNA. These transcripts have an organization similar to that of somatic cell nuclear RNA. Data are presented that suggests some of these interspersed maternal transcripts are unprocessed precursor-like molecules. Some possible functions of this novel class of RNA during early development are discussed.

Animals↗
PubMed1981

Long and short repeats of sea urchin DNA and their evolution.

Repeated sequences cloned from the DNA of the sea urchin S. purpuratus were used as probes to measure the lengths of individual families of repeats. Some probes reassociated much more rapidly with preparations of long repeats than with short repeats while others reassociated more rapidly with short repeats than with long repeats. In this way two of five cloned repeats were shown to represent families with a great majority of sequences in the long class. One represented a family with similar number of long and short class members. Two were members of predominantly short class families - The cloned repeats representing long class families, formed more precise duplexes than those representing short class families. Thermal stability measurements using S. purpuratus or S. franciscanus driver DNA showed that precise repetitive sequences have as great an interspecies sequence difference as the less precise repeats. Thus the precision of many families may result from recent multiplication rather than from selective pressure on the DNA sequences. Measurements of evolutionary frequency change show a clear correlation between the frequency change and the size of families of repeats in S. purpuratus. Comparison with S. franciscanus indicates that many of the large size families in S. purpuratus are those that have grown in size since these two species diverged.

Animals↗
PubMed1981

Organization and expression of multiple actin genes in the sea urchin.

A set of at least 11 actin genes has been isolated from genomic recombinant deoxyribonucleic acid libraries of the sea urchin Strongylocentrotus purpuratus. Most of the isolates derive from a library which represents the genome of a single animal. There are at least five distinct types of sea urchin actin gene, some of which are represented by multiple copies in the genome. The actin gene types are distinguished by nonhomologous flanking sequences and intervening sequences, though the protein coding sequences appear in most cases to be quite similar. Eight of the 11 genes isolated have been recovered in lambda recombinants that contain two actin genes, linked at 5- to 9-kilobase distances. Restriction map overlaps suggest that the genome contains an array of at least three of these genes spaced over about 30 kilobases of deoxyribonucleic acid. In the linkage patterns observed, actin genes of diverse types were linked to each other. In early embryos, actin messenger ribonucleic acid (RNA) transcripts of 1.8 and 2.2 kilobases were found, and the longer of these transcripts was more prevalent in the maternal RNA of the egg. From RNA gel blot experiments, we conclude that the two transcripts derive from different actin gene types. Different repetitive sequences were located to either side of most of the actin genes, and in most observed cases the repeat sequences which were adjacent to actin genes of a given type were similar. The repeat sequences flanking the actin genes belonged to families which were transcribed, but those repeats in the neighborhood of the actin genes which have been investigated were not themselves represented in the stable RNAs of eggs or early embryos.

Actins↗
PubMed1980

Evolutionary conservation of repetitive sequence expression in sea urchin egg RNA's.

Cloned repetitive DNA sequences were used to determine the number of homologous RNA transcripts in the eggs of two sea urchin species, Strongylocentrotus purpuratus and S. franciscanus. The eggs of these species contain different amounts of RNA, and their genomes contain different numbers of copies of the cloned repeats. The specific pattern of repetitive sequence representation in the two egg RNA's is nonetheless quantitatively similar. The evolutionary conservation of this pattern suggests the functional importance of repeat sequence expression.

Animals↗
PubMed1980

Evolution of sea urchin non-repetitive DNA.

New methods have been applied to the determination of single copy DNA sequence differences between the sea urchin species Strongylocentrotus purpuratus, S. franciscanus, S. drobachiensis, and Lytechinus pictus. The thermal stability of interspecies DNA duplexes was measured in a solvent (2.4 M tetraethylammonium chloride) that suppresses the effect of base composition on melting temperature. The lengths of duplexes were measured after digestion with S1 nuclease and correction made for the effect of length on thermal stability. The degree of base substitution that has occurred in the single copy DNA during sea urchin evolution is significantly larger than indicated by earlier measurements. We estimate that 19% of the nucleotides of the single copy DNA are different in the genomes of the two sea urchin congeners, S. purpuratus, and S. franciscanus, which apparently diverged only 15 to 20 million years ago.

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