Suza, Walter , Chappell, Joe .
Investigating the regulation of sterol biosynthesis in Nicotiana benthamiana.
Sterols are products of the mevalonate (MVA) pathway and are known to serve a wide range of functions in plants. Sterols are key components in regulating membrane fluidity and permeability, and key to the integrity of membrane micro-domains known as lipid rafts. This structurally-conserved class of lipids also serves as the precursors to steroid hormones in plants, as in mammals, insects, and crustaceans. Although a large body of information about the regulation of sterol biosynthesis is available for the well-characterized mammalian and yeast systems, the regulation of this biochemical pathway in plants is not well understood and many outstanding questions remain unanswered. For instance, mammals and yeast produce a single major sterol, cholesterol, and ergosterol respectively. However, plants produce a complex array of sterols with indications that specific sterols accumulate preferentially in some tissues to particular levels but not others. How the biosynthesis and accumulation of select sterol species in specific tissues, organs or cell types is regulated remains unexplored. In the current study, we are utilizing Nicotiana benthamiana as model to investigate spatial and developmental relationship between sterol synthesis rates and sterol content. Specifically our study aims to: (1) compare tissue-specific expression of key MVA pathway genes; (2) measure tissue-specific activity of selected MVA pathway enzymes; (3) utilize isotope-labeled precursors of sterols to evaluate sterol synthesis rates in selected tissues and; (4) determine sterol content of selected tissues. The current data suggest, for instance, that sterol biosynthesis is greatest in young leaves and roots, tissues with the largest number of rapidly dividing cells, and greatly diminished in more mature tissues. Different ratios of campesterol, stigmasterol and sitosterol accumulate in these tissues as well. From the molecular level, transcript levels for many of the biosynthetic enzymes remain constant, hence suggesting that some sort of post-translational regulation must be occurring. Our data is helping to identify spatial and developmental control points of sterol biosynthesis in a plant system that allows for easy genetic manipulations for assessing the contribution of specific enzymes to sterol accumulation, and the contributions of select sterols to the physiology of plant cells, tissues and organs.
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1 - University of Kentucky, Plant and Soil Sciences, 1405 Veterans Drive, Lexington, Kentucky, 40546, USA
2 - University of Kentucky, Plant and Soil Sciences
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM