Galante, Michael , MacLean, Brittany , Dean, Nathan , Papsidero, Tim , Carpenter, Caitlin , Becker, David , Grebenok, Robert .
Determination of sterol species and levels that provide localized enhancement of electron transport rates in tobacco thylakoid membranes.
The objective of this project is to examine the role(s) played by various sterol types and their titers on photosynthetic electron transport rates. We employ transgenic lines of tobacco that express a microbial 3-hydroxysteroid oxidase (a.k.a. cholesterol oxidase) gene, whose gene product is localized to the chloroplast. Products of the enzyme action include the 3 keto- derivatives of sitosterol, stigmasterol, campesterol and cholesterol, and these oxidized steroids make up approximately 70% of the total steroid composition of the transgenic thylakoid membranes. We detect no oxidized steroids in control thylakoids even though total steroid contents of control and transgenic thylakoids are comparable. The modified steroid profile of transgenic thylakoids is coincident with elevated rates of in vitro light saturated whole chain electron transport (WCET) compared to WCET rates in control thylakoids. In vitro equilibrations of individual sterols into thylakoids from both lettuce and control tobacco result in enhanced WCET rates similar to those measured in transgenic thylakoids. Excess sterol incorporation, however, results in decreased WCET rates. Thus we link specific sterols and titers to role(s) in photosynthetic electron transport. We will discuss sterol specificity as well as localization of the steroid effect to PS I and/or PS II.
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1 - Canisius College, Biology, 2001 Main St, Buffalo, New York, 14208, U.S.A
2 - Canisius College, Department of Biology
3 - Pomona College, Department of Biology
photosynthetic electron transport
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM