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BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES

Metabolite Sorting of a Germplasm Collection Reveals the Hydroxylase3 Locus as a New Target for Maize Provitamin A Biofortification^{1,[C],[W],[OA]}

Department of Biological Sciences, Lehman College, City University of New York, Bronx, New York 10468 (R.V., C.E.G., N.L., A.J.C., R.F.Q., E.T.W.); and Graduate School and University Center, City University of New York, New York, New York 10016–4309 (R.V., R.F.Q., E.T.W.)

Vitamin A deficiency, a global health burden, can be alleviated through provitamin A carotenoid biofortification of major crop staples such as maize (Zea mays) and other grasses in the Poaceae. If regulation of carotenoid biosynthesis was better understood, enhancement could be controlled by limiting β-carotene hydroxylation to compounds with lower or no nonprovitamin A activity. Natural maize genetic diversity enabled identification of hydroxylation genes associated with reduced endosperm provitamin A content. A novel approach was used to capture the genetic and biochemical diversity of a large germplasm collection, representing 80% of maize genetic diversity, without having to sample the entire collection. Metabolite data sorting was applied to select a 10-line genetically diverse subset representing biochemical extremes for maize kernel carotenoids. Transcript profiling led to discovery of the Hydroxylase3 locus that coincidently mapped to a carotene quantitative trait locus, thereby prompting investigation of allelic variation in a broader collection. Three natural alleles in 51 maize lines explained 78% of variation and approximately 11-fold difference in β-carotene relative to β-cryptoxanthin and 36% of the variation and 4-fold difference in absolute levels of β-carotene. A simple PCR assay to track and identify Hydroxylase3 alleles will be valuable for predicting nutritional content in genetically diverse cultivars found worldwide.

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: Eleanore T. Wurtzel (wurtzel{at}lehman.cuny.edu).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[W] The online version of this article contains Web-only data.

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

www.plantphysiol.org/cgi/doi/10.1104/pp.109.145177

^* Corresponding author; e-mail wurtzel{at}lehman.cuny.edu.

Received July 22, 2009; accepted September 8, 2009; published September 18, 2009.