Molecular characterization of the Camptotheca acuminata (Decaisne) 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) gene family /
Camptotheca acuminata is a Chinese tree that produces the anti-cancer monoterpenoid indole alkaloid camptothecin (CPT). In addition to its general role in isoprenoid biosynthesis, 3-hydroxy3-methylglutaryl Coenzyme A reductase (HMGR) supplies mevalonate for the terpenoid moiety of CPT and its deriva...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739669511&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Camptotheca acuminata is a Chinese tree that produces the anti-cancer monoterpenoid indole alkaloid camptothecin (CPT). In addition to its general role in isoprenoid biosynthesis, 3-hydroxy3-methylglutaryl Coenzyme A reductase (HMGR) supplies mevalonate for the terpenoid moiety of CPT and its derivatives. A gene encoding HMGR (hmg1) was previously isolated and characterized from C. acuminata (Burnett et al., 1993). This work describes the isolation and analysis of a genomic (hmg2) and a CDNA (hmg3) clone encoding two other members of the C. acuminata HMGR gene family. Levels of HMGR transcript in various C. acuminata tissues showed a correlation of two family members (hmg1 and hmg3) with the accumulation of CPT and 10-OH-CPT. Levels of hmg3 MRNA also correlated with the accumulation of 10-OH-CPT during germination. In C. acuminata, hmg1 transcripts are induced by wounding, and this induction is suppressed by methyl jasmonate (MeJA), as previously reported in transgenic tobacco (Burnett et al., 1993). Regulation of the hmg2 promoter was studied using hmg2::GUS translational fusions in transgenic tobacco. Histochemical analysis showed GUS staining in the stalks of glandular trichomes, leaf veins, epidermal cells of roots, pollen, style, abscission zone of petals and stamens, and in immature seeds and their associated vasculature in fruits. Promoter studies showed that the minimal promoter of hmg2 is contained in a region of only 86 bp. MeJA and light treatments showed transcriptional suppression of hmg2::GUS expression in transgenic tobacco, but did not affect hmg2 MRNA levels in C. acuminata tissues. These results show that HMGR family members are differentially expressed in C. acuminata and transgenic tobacco tissues under diverse physiological conditions, supporting the hypothesis that specific HMGR isozymes might be involved in the synthesis of CPT in different C. acuminata tissues. |
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| Item Description: | Vita. "Major Subject: Biology". In title, numerals are used. |
| Physical Description: | xi, 106 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 92-104. |