A characterization of the conjusome : a new organelle in Tetrahymena thermophila found exclusively during sexual reorganization /
A new organelle, the conjusome, has been identified and characterized in Tetrahymena thermophila. The conjusome appears only during a specific phase of conjugation. Transmission electron microscopic observations reveal that the conjusome is not a membrane-bounded structure. The conjusome ranges in s...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=733675651&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | A new organelle, the conjusome, has been identified and characterized in Tetrahymena thermophila. The conjusome appears only during a specific phase of conjugation. Transmission electron microscopic observations reveal that the conjusome is not a membrane-bounded structure. The conjusome ranges in size from about 1[]m to sizes approaching 7 []m, depending on its maturity. It is composed of a coarse reticulum of a fibrous, electron dense material, interspersed with apparent background cytoplasm and ribosomes. Immunofluorescence microscopy reveals that the conjusome is strongly labeled by antibodies to the protein Pdd1p. Pdd1p is a chromodomain protein and participates in the formation of chromatin-containing structures in developing macronuclear anlagen. Recent studies suggest that Pdd1p is physically associated with the elimination of specific germ-line sequences from developing macronuclei (anlagen) and may play a role in heterochromatin assembly. The conjusome contains Pdd1p, but it is devoid of any detectable DNA. The conjusome appears before DNA elimination begins in the developing antigen and after Pdd1p is found in the parental macronucleus. Conjugants containing a knock out of the PDD1 allele in the parental macronucleus do not show Pdd1p antibody staining in conjusomes. Investigations were done using the conjugation mutants cnj9 and cnj10 and wild type cells that were blocked with the drugs aphidicholine and cycloheximide. The data obtained from these experiments showed that once conjugation was initiated, fertilization was not a requirement for conjusome development or anlagen determination. In addition, compelling evidence suggests that the conjusome shuttles Pdd1p, and possible other components, from the parental macronucleus to the macronuclear antigen. This data, taken together with repent Pdd1p knockout experiments, suggests the conjusome might be involved in the epigenetic phenomena that occur during conjugation and sexual reorganization. |
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| Item Description: | Vita. "Major Subject: Biology". |
| Physical Description: | xiv, 144 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 127-142). |