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Localization of key enzymes in alkaloid producing plants: Tryptophan synthase [Beta] in Camptotheca acuminata and tyrosine decarboxylase in Papaver somniferum
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Compartmentation of plant products and their biosynthetic pathways occurs at both the cellular and subcellular levels in a highly regulated fashion. As part of the investigation into the compartmentation of alkaloid biosynthetic pathways, two enzymes, tryptophan synthase β (TSB) and tyrosine decarboxylase (TyDC), have been localized in Camptotheca acuminata and Papaver somniferum respectively. In C. acuminata, TSB plays a role in the biosynthesis of the monoterpene indole alkaloid camptothecin (CPT). Subcellular localization of TSB using immunogold labeling was conducted in different tissue parts of a two year old tree and thirty day old seedlings. In the tree leaf tissue, TSB was localized to the chloroplasts of the palisade cells. In the seedling tissue, TSB was localized to the chloroplasts of the palisade cells as well as the plastids and nuclei of the xylem parenchyma in the leaves. In the seedling stem, TSB was localized to the chloroplasts and some nuclei of the xylem parenchyma. In the seedling root, TSB was localized to the plastids of the xylem parenchyma but mostly to the plastids of the outer cortical cells. In Papaver somiferum, TyDC is involved in the biosynthesis of the isoquinolone alkaloids. TyDC also plays a part in the defense response system of plants as part of the biosynthetic pathway of cell wall-bound amides. Transgenic TyDC5::GUS opium poppy and tobacco plants were examined for GUS staining, as an indication of the cellular localization of TyDC5. GUS expression was localized to the xylem parenchyma of both opium poppy and tobacco in the shoot tissue. In the root tissue, GUS expression was localized to the pericycle in opium poppy and in most of the vascular tissue in tobacco. The effect of wounding and methyl jasmonate (MJ) on the expression levels of TyDC5::GUS was assayed in the root and leaf tissue of both transgenic opium poppy and tobacco. TyDC5 was shown to be induced by both wounding and MJ in opium poppy. In tobacco, although most of the plants examined showed an induced response to both effects, MJ showed some suppression to wound induced expression in some plants.
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Includes bibliographical references (leaves 69-78).
Issued also on microfiche from Lange Micrographics.
El-Ahmady, Sherweit Hamed (2000). Localization of key enzymes in alkaloid producing plants: Tryptophan synthase [Beta] in Camptotheca acuminata and tyrosine decarboxylase in Papaver somniferum. Master's thesis, Texas A&M University. Available electronically from
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