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A WD40 Repeat Protein from Medicago truncatula Is Necessary for Tissue-Specific Anthocyanin and Proanthocyanidin Biosynthesis But Not for Trichome Development^1,[W],[OA]

Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (Y.P., G.J.P., J.W., D.H., S.N.A., Y.T., X.C., M.T., K.S.M., L.W.S., R.A.D); Department of Genetics and Cell Biology, University of Minnesota, St. Paul, Minnesota 55108 (J.P.W., K.S., M.D.M.); and Institut des Sciences du Vegetale, CNRS, 91198 Gif sur Yvette, France (P.R.)

WD40 repeat proteins regulate biosynthesis of anthocyanins, proanthocyanidins (PAs), and mucilage in the seed and the development of trichomes and root hairs. We have cloned and characterized a WD40 repeat protein gene from Medicago truncatula (MtWD40-1) via a retrotransposon-tagging approach. Deficiency of MtWD40-1 expression blocks accumulation of mucilage and a range of phenolic compounds, including PAs, epicatechin, other flavonoids, and benzoic acids, in the seed, reduces epicatechin levels without corresponding effects on other flavonoids in flowers, reduces isoflavone levels in roots, but does not impair trichome or root hair development. MtWD40-1 is expressed constitutively, with highest expression in the seed coat, where its transcript profile temporally parallels those of PA biosynthetic genes. Transcript profile analysis revealed that many genes of flavonoid biosynthesis were down-regulated in a tissue-specific manner in M. truncatula lines harboring retrotransposon insertions in the MtWD40-1 gene. MtWD40-1 complemented the anthocyanin, PA, and trichome phenotypes of the Arabidopsis (Arabidopsis thaliana) transparent testa glabrous1 mutant. We discuss the function of MtWD40-1 in natural product formation in M. truncatula and the potential use of the gene for engineering PAs in the forage legume alfalfa (Medicago sativa).

² Present address: Calgene/Monsanto, 1920 5th Street, Davis, CA 95616.

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: Richard A. Dixon (radixon{at}noble.org).

^[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.109.144022

^* Corresponding author; e-mail radixon{at}noble.org.

Received June 30, 2009; accepted August 21, 2009; published August 26, 2009.