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BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES

Identification of an Arabidopsis Feruloyl-Coenzyme A Transferase Required for Suberin Synthesis^1,[W],[OA]

Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824

All plants produce suberin, a lipophilic barrier of the cell wall that controls water and solute fluxes and restricts pathogen infection. It is often described as a heteropolymer comprised of polyaliphatic and polyaromatic domains. Major monomers include -hydroxy and ,-dicarboxylic fatty acids, glycerol, and ferulate. No genes have yet been identified for the aromatic suberin pathway. Here we demonstrate that Arabidopsis (Arabidopsis thaliana) gene AT5G41040, a member of the BAHD family of acyltransferases, is essential for incorporation of ferulate into suberin. In Arabidopsis plants transformed with the AT5G41040 promoter:YFP fusion, reporter expression is localized to cell layers undergoing suberization. Knockout mutants of AT5G41040 show almost complete elimination of suberin-associated ester-linked ferulate. However, the classic lamellar structure of suberin in root periderm of at5g41040 is not disrupted. The reduction in ferulate in at5g41040-knockout seeds is associated with an approximate stoichiometric decrease in aliphatic monomers containing -hydroxyl groups. Recombinant AT5G41040p catalyzed acyl transfer from feruloyl-coenzyme A to -hydroxyfatty acids and fatty alcohols, demonstrating that the gene encodes a feruloyl transferase. CYP86B1, a cytochrome P450 monooxygenase gene whose transcript levels correlate with AT5G41040 expression, was also investigated. Knockouts and overexpression confirmed CYP86B1 as an oxidase required for the biosynthesis of very-long-chain saturated ,-bifunctional aliphatic monomers in suberin. The seed suberin composition of cyp86b1 knockout was surprisingly dominated by unsubstituted fatty acids that are incapable of polymeric linkages. Together, these results challenge our current view of suberin structure by questioning both the function of ester-linked ferulate as an essential component and the existence of an extended aliphatic polyester.

² Present address: Unité Mixte de Recherche 5200, Centre National de la Recherche Scientifique/University of Bordeaux, F–33076 Bordeaux, France.

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: Mike Pollard (pollard9{at}msu.edu).

^[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.109.144907

^* Corresponding author; e-mail pollard9{at}msu.edu.

Received July 16, 2009; accepted September 13, 2009; published September 16, 2009.

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