l-Tartaric acid synthesis from vitamin C in higher plants

doi:10.1073/pnas.0510864103

l-Tartaric acid synthesis from vitamin C in higher plants

*School of Agriculture, Food, and Wine, University of Adelaide, Adelaide, SA 5005, Australia;
^†Department of Plant Pathology, University of California, Davis, CA 95616-8680; and
^‡Cooperative Research Centre for Viticulture, P.O. Box 145, Glen Osmond, SA 5064, Australia

Edited by Luis Herrera-Estrella, National Polytechnic Institute, Guanajuato, Mexico, and approved February 3, 2006 (received for review December 15, 2005)

Abstract

The biosynthetic pathway of l-tartaric acid, the form most commonly encountered in nature, and its catabolic ties to vitamin C, remain a challenge to plant scientists. Vitamin C and l-tartaric acid are plant-derived metabolites with intrinsic human value. In contrast to most fruits during development, grapes accumulate l-tartaric acid, which remains within the berry throughout ripening. Berry taste and the organoleptic properties and aging potential of wines are intimately linked to levels of l-tartaric acid present in the fruit, and those added during vinification. Elucidation of the reactions relating l-tartaric acid to vitamin C catabolism in the Vitaceae showed that they proceed via the oxidation of l-idonic acid, the proposed rate-limiting step in the pathway. Here we report the use of transcript and metabolite profiling to identify candidate cDNAs from genes expressed at developmental times and in tissues appropriate for l-tartaric acid biosynthesis in grape berries. Enzymological analyses of one candidate confirmed its activity in the proposed rate-limiting step of the direct pathway from vitamin C to tartaric acid in higher plants. Surveying organic acid content in Vitis and related genera, we have identified a non-tartrate-forming species in which this gene is deleted. This species accumulates in excess of three times the levels of vitamin C than comparably ripe berries of tartrate-accumulating species, suggesting that modulation of tartaric acid biosynthesis may provide a rational basis for the production of grapes rich in vitamin C.

Footnotes

^§To whom correspondence should be addressed. E-mail: christopher.ford{at}adelaide.edu.au
Author contributions: S.D., D.R.C., and C.M.F. designed research; S.D. and C.M.F. performed research; D.R.C. contributed new reagents/analytic tools; S.D. and D.R.C. analyzed data; and S.D., D.R.C., and C.M.F. wrote the paper.
Conflict of interest statement: No conflicts declared.
This paper was submitted directly (Track II) to the PNAS office.
Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. DQ124868).
Abbreviations:

Abbreviations:

TA,

l-tartaric acid;

AA,

l-ascorbic acid;

OxA,

oxalic acid;

l-IdnDH,

l-idonate dehydrogenase.