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Abstract Detail


Secondary Metabolism

Rasbery, Jeanne [1], Shan, Hui [2], Thompson, Mary Kay [3], Matsuda, Seiichi P.T. [2], Bartel, Bonnie [3].

Arabidopsis thaliana SQUALENE EPOXIDASE 1 is essential for root and seed development.

Terpenes constitute the largest group of plant natural products, yet the biological functions of most of these compounds remain unknown. Members of the triterpenoid family include hormones (brassinosteroids) and membrane sterols, which function in plant development and membrane fluidity, respectively. Squalene epoxidase converts squalene into oxidosqualene, the precursor of all known plant sterols. The Arabidopsis genome contains six genes predicted to encode squalene epoxidases. This apparent redundancy suggests these homologs may have different substrate or product specificity, altered catalytic properties, or unique expression patterns. Through heterologous expression in yeast, we have demonstrated that three SQE enzymes, SQE1, SQE2, and SQE3, are bona fide squalene epoxidases. GC-MS analysis of the products of the remaining SQE enzymes may pinpoint specific roles for these enzymes as well.
We isolated loss-of-function mutations in each of the Arabidopsis squalene epoxidase homologs. sqe1 plants have severe root elongation defects and produce inviable seeds. In addition, sqe1 mutants accumulate squalene, suggesting triterpenoid biosynthesis is blocked in these plants. These data indicate an essential role for SQE1 in normal plant development, and that other Arabidopsis SQE enzymes are not fully redundant with SQE1. Indeed, gene expression analysis has revealed unique and overlapping expression patterns among the Arabidopsis SQE genes. This work was supported by the NSF 2010 program and the National Institutes of General Medical Sciences Training Grant GM 08362.


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1 - Rice University, Biochemistry & Cell Biology, 6100 Main St, MS-140, Houston, TX, 77005, United States
2 - Rice University, Chemistry
3 - Rice University, Biochemistry & Cell Biology

Keywords:
terpene
triterpenoid
squalene epoxidase.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P20016
Abstract ID:301


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