Steroid profiles of transgenic tobacco expressing an Actinomyces 3-hydroxysteroid oxidase gene

The action of a 3-hydroxysteroid oxidase enzyme within mature vegetative transgenic tobacco alters the resident sterol pool facilitating the enhanced accumulation of sterol, 3-ketosteroid and stanol throughout the plant. The modulated steroid pool correlates directly with altered thylakoid membrane-...

Full description

Saved in:

Bibliographic Details
Published in:	Phytochemistry (Oxford) Vol. 65; no. 22; pp. 2967 - 2976
Main Authors:	Heyer, Jennelle, Parker, Brandon, Becker, David, Ruffino, John, Fordyce, Amber, Witt, Matt De, Bedard, Mark, Grebenok, Robert
Format:	Journal Article
Language:	English
Published:	Amsterdam Elsevier Ltd 01-11-2004 Elsevier
Subjects:	3-Hydroxysteroid Dehydrogenases - metabolism 3-Hydroxysteroid oxidase 3-Ketosteroid Actinomyces Actinomyces - enzymology bacterial proteins Biological and medical sciences Campesterol Chemical constitution Chlorophyll - metabolism Chloroplast Chloroplasts - metabolism Cholesterol Electron Transport Fundamental and applied biological sciences. Psychology gene expression Gene Expression Regulation, Plant lipid content Metabolism Metabolism. Physicochemical requirements Nicotiana - genetics Nicotiana - metabolism Nicotiana tabacum oxidoreductases Photosynthesis phytosterols Plant physiology and development Plants, Genetically Modified Sitosterol Stanol steroids Steroids - metabolism Stigmasterol Tobacco transgenes Transgenic transgenic plants Sitosterol Tobacco Stigmasterol Campesterol 3-Hydroxysteroid oxidase Transgenic Stanol 3-Ketosteroid Nicotiana tabacum Photosynthesis Cholesterol Chloroplast Steroid Campcsterol Whole plant Chlornplast In vitro Gene Dicotyledones Angiospermae Spermatophyta Transgenic plant Solanaceae Sterol
Online Access:	Get full text
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	The action of a 3-hydroxysteroid oxidase enzyme within mature vegetative transgenic tobacco alters the resident sterol pool facilitating the enhanced accumulation of sterol, 3-ketosteroid and stanol throughout the plant. The modulated steroid pool correlates directly with altered thylakoid membrane-associated biochemical processes, in which the in vitro rate of whole chain photosynthetic electron transport is enhanced at reduced environmental temperatures. Previously, we have shown that the expression of a 3-hydroxysteroid-oxidase gene in transgenic tobacco initiated a series of biochemical events leading to the conversion of sterol to stanol. As a result, the plants maintained a diminished sterol pool and a modified relative sterol ratio but demonstrated no observable morphological abnormalities. The maintenance of normal higher plant physiology in the absence of particular sterols or in the presence of modified sterol ratios is controversial. In this report, we present additional biochemical and physiological characteristics of transgenic tobacco expressing an Actinomyces 3-hydroxysteroid-oxidase gene. The total steroid accumulated in the transgenic plants is 6-fold higher than in control plants and consists of sterol, 3-ketosteroid and stanol. The relative abundance of sterols within whole plant and individual organs is grossly altered as ethylated side chain sterols account for 99% of the total sterol pool in the transgenic tobacco. Stigmasterol is readily apparent in all tissues and cholesterol is found at measurable levels in specific organs, while campesterol and sitosterol are detected at trace levels in the transgenic plants. Stanols and 3-ketosteroids accumulate in all tissues and represent 77% of the measurable steroid pool in the transgenic plants. The sum of sterol, the respective 3-ketosteroid plus stanol provide a relative abundance of steroid, which is similar to the abundance of sterol accumulated in control tissue. In vitro photosynthetic electron transport measurements demonstrate altered activity of chloroplasts under a variety of reaction conditions, indicating a link between the modified steroid pool and a modulation of chloroplast membrane function.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0031-9422 1873-3700
DOI:	10.1016/j.phytochem.2004.09.012