Isolation and characterization of tryptophan synthase beta and anthranilate synthase alpha genes from the early indole metabolism in Camtotheca acuminata /
Camptothecin is an important anticancer drug produced by the monoterpene indole alkaloid pathway in Camptotheca acuminata. As part of an investigation into the camptothecin biosynthesis pathway, two genes involved in the early biosynthesis of camptothecin, the tryptophane synthase beta gene (TSB) an...
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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=733674391&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Camptothecin is an important anticancer drug produced by the monoterpene indole alkaloid pathway in Camptotheca acuminata. As part of an investigation into the camptothecin biosynthesis pathway, two genes involved in the early biosynthesis of camptothecin, the tryptophane synthase beta gene (TSB) and the anthranilate synthase alpha gene (ASA), were cloned from Camptotheca acuminata and their expression was analyzed. In Camptotheca, the TSB gene is a single copy (CaTSB1) while the ASA gene had two very closely related copies (CaASA1 and CaASA2). The Camptotheca ASA and TSB demonstrated a high similarity to the corresponding proteins from microorganisms and other plants. In a one-year old Camptotheca tree, TSB and ASA proteins had very similar accumulation patterns in all organs examined, and their abundance paralleled that of camptothecin. Localization of the TSB protein was detailed by tissue printing and was found to be most abundant in vascular tissues and the outer cortex of roots in Camptotheca. Expression of the TSB and ASA promoters from Camptotheca was studied in transgenic tobacco. Reporter gene activity (beta-glucuronidase) driven by the TSB promoter was detected in the vascular tissue of stem, petiole and seedlings in transgenic tobacco plants. This pattern paralleled expression of the native gene in Camptotheca in all organs except roots. In addition, expression of CaASA1::GUS was found in the peduncle of a flower, the anther including pollen grains and in suspension cultures induced from transgenic tobacco plants. CaASA1::GUS plants demonstrated similar vascular tissue-associated GUS expression. CaASA2::GUS plants, on the other hand, showed relatively weaker GUS activity in vegetative tissues but a stronger expression in reproductive tissues. Seedling growth is a very vulnerable stage during plant development. As a compound with an apparent defensive function, CPT is induced rapidly during seedling germination. This accumulation of camptothecin is preceded by a transient induction of both the CaTSB1 and CaASA1 genes. The co-induction of the two tryptophan pathway genes and CPT accumulation is consistent with the idea that tryptophan biosynthesis and the secondary insole alkaloid pathway are coordinately regulated. |
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| Item Description: | Vita. "Major Subject: Biology". |
| Physical Description: | xi, 102 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 91-101). |