OPEN ACCESS ARTICLE

This Article Free via Open Access: OA OA Full Text Full Text (PDF) OA All Versions of this Article: 149/2/1042    most recent pp.108.130948v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Endres, S. Articles by Tenhaken, R. Search for Related Content PubMed PubMed Citation Articles by Endres, S. Articles by Tenhaken, R. Agricola Articles by Endres, S. Articles by Tenhaken, R.

BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES

Myoinositol Oxygenase Controls the Level of Myoinositol in Arabidopsis, But Does Not Increase Ascorbic Acid^1,[OA]

University of Salzburg, 5020 Salzburg, Austria

Ascorbic acid (AsA) is a major plant antioxidant. Mutants like vtc1 show a reduced AsA concentration, which confirmed by genetic evidence the previously proposed AsA pathway via GDP-Man. Here we investigate the role of an animal-like alternative biosynthesis route to AsA, starting from the metabolite D-GlcUA, which is produced in plants by myoinositol oxygenase (Miox). Miox-overexpressing lines have a more than 30-fold up-regulated transcript level and higher enzymatic activity as shown by increased incorporation of Miox-derived sugars into cell wall polymers. In addition, Miox overexpressors exhibit a lower steady-state level of myoinositol and accumulate less myoinositol in feeding experiments due to an enhanced turnover rate. The AsA concentration remains the same in wild-type and Miox overexpressor lines. Even challenging plants with stress, which increases AsA concentration 4-fold, reveals no difference in AsA biosynthesis between wild-type and Miox-overexpressing lines. We conclude that D-GlcUA derived from the Miox reaction plays a negligible role for AsA biosynthesis. However, Miox controls the metabolite level of myoinositol in plants.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Raimund Tenhaken (raimund.tenhaken{at}sbg.ac.at).

^[OA] Open access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.108.130948

^* Corresponding author; e-mail raimund.tenhaken{at}sbg.ac.at.

Received October 9, 2008; accepted December 16, 2008; published December 17, 2008.