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C G Wray

Publications and source records attributed to C G Wray.

5 recordsLinked to original sources
PubMed1995

Homologues of the engrailed gene from five molluscan classes.

We used the polymerase chain reaction (PCR) to amplify, clone, and sequence 10 engrailed homeodomains from 8 species in the five major molluscan classes, including the serially organized chiton (Polyplacophora) lineage. The Drosophila melanogaster gene engrailed (en) is one of several genes involved in embryonic segment polarity determination. Studies of engrailed sequence and expression in molluscs are of interest due to questions regarding the evolution and homology of segmentation in these taxa. Nucleotide and deduced amino acid sequence comparisons reflect evolutionary conservation within helices of the en homeodomain and ancient divergences in the region 3' to the homeodomain.

Animals↗
PubMed1995

Origin of the foraminifera.

We report nuclear small-subunit rDNA sequences for two species of the benthic foraminifer Ammonia. Because of their abundance in present and past seas, the foraminifera are a very important group of organisms used in a wide range of geologic studies; however, the ancestry of this group was, until now, unknown. Difficulties in purifying foraminiferal DNA and avoiding PCR contamination led us to develop DNA.DNA in situ hybridization techniques to verify our sequence data. Phylogenetic analysis of verified foraminiferal DNA sequence indicates these taxa are a divergent, "alveolate" lineage, within the major eukaryotic radiation. Our findings cast doubt upon the assumption that all foraminifera are derived from an amoebalike ancestor. Cytological features and the DNA sequences presented herein suggest that the foraminifera were derived from a heterokaryotic flagellated marine protist, probably sometime in the later Proterozoic.

Animals↗
PubMed1994

Phylogenetic utility of ubiquitin DNA sequence from 3 marine protist lineages.

The foraminifera are one of the last major groups of eukaryotes for which no published DNA sequences exist. DNA sequence of ubiquitin repeat units from 5 foraminifera (representing 3 suborders), a diatom, and a dinoflagellate were characterized using the polymerase chain reaction, cloning, and sequencing. The phylogenetic utility of ubiquitin DNA sequence is discussed in reference to a full eukaryote data base. The foraminifera are possibly a polyphyletic group, whereas the phylogenetic placement of the diatom and the dinoflagellate are congruent with existing hypotheses. The lack of a noneukaryote root and limited phylogenetically informative sequence information indicate that polyubiquitin may not be useful for phylogenetic reconstruction of all eukaryotes.

Amino Acid Sequence↗
PubMedDate not supplied

Molluscan engrailed expression, serial organization, and shell evolution.

Whether the serial features found in some molluscs are ancestral or derived is considered controversial. Here, in situ hybridization and antibody studies show iterated engrailed-gene expression in transverse rows of ectodermal cells bounding plate field development and spicule formation in the chiton, Lepidochitona cavema, as well as in cells surrounding the valves and in the early development of the shell hinge in the clam, Transennella tantilla. Ectodermal expression of engrailed is associated with skeletogenesis across a range of bilaterian phyla, suggesting a single evolutionary origin of invertebrate skeletons. The shared ancestry of bilaterian-invertebrate skeletons may help explain the sudden appearance of shelly fossils in the Cambrian. Our interpretation departs from the consideration of canonical metameres or segments as units of evolutionary analysis. In this interpretation, the shared ancestry of engrailed-gene function in the terminal/posterior addition of serially repeated elements during development explains the iterative expression of engrailed genes in a range of metazoan body plans.

Animals↗