Two genes from adult, female Blaberus discoidalis cockroaches : molecular cloning, expression profiles, and suppression by juvenile hormone /
Efforts to identify genes expressed strongly in the absence of juvenile hormone (JH), but expressed only n-minimally in the presence of JH in the fat body of adult, female Blaberus discoidalis cockroaches led to the isolation and identification of two cDNAs representing JH-suppressible mRNAs. Seque...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742744281&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Efforts to identify genes expressed strongly in the absence of juvenile hormone (JH), but expressed only n-minimally in the presence of JH in the fat body of adult, female Blaberus discoidalis cockroaches led to the isolation and identification of two cDNAs representing JH-suppressible mRNAs. Sequence analysis indicated that both cDNAs represent large, well-characterized protein families: the transferrins and the hexamerins. Transferrins are iron-binding/transport proteins while hexamerins are a family of arthropod proteins characterized by their -500 kDa holoprotein structure of six homologous subunits. A genomic library screened with the arylphorin and transfenin cDNAs yielded clones containing the 5' flanking regulatory regions of both structural genes. Sequence analysis and transcription factor response element searches indicate numerous putative response elements. Efforts are in progress to characterize the regulatory regions of DNA responsible for JH-suppression of these mRNAs. Surgical removal of the corpora allata, the glandular source of JH, produces JH deficient (JH-) insects. In JH- animals transfenin (Tf) and arylphorin (Ar) transcripts accumulate to levels 30-70 fold higher than in JH+ animals, where they are almost nonexistent. Treatment of JH- insects with synthetic JH restores steady-state levels of both transcripts to those of normal and sham-operated (JH+) insects. One of the primary JH functions in many adult insects is stimulation of expression of yolk protein (vitellogenin) genes during o6genesis. Fluctuations in the steady-state MRNA profiles of Tf and Ar mRNAs through the first cycle of vitebogenesis in normalmated females are dramatic. JH is absent during metamorphosis. Accordingly, on the first day of adulthood (day 0), levels of both transcripts are high. As Vg synthesis begins (day 2), transcript levels are suppressed to near undetectability and remain low until the end of vitellogenesis (day 18-21). At the end of vitellogenesis, both transcripts rapidly accumulate and remain high through day 35. Related work on the mechanism by which JH stimulates high-level accumulation of two vitellogenin mRNAs makes this a novel system, displaying both positive and negative aspects of JH action on diverse genes in the same tissue at the same time. |
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| Item Description: | Vita. "Major Subject: Biology". |
| Physical Description: | ix, 91 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |