Gene Coexpression Analysis Reveals Complex Metabolism of the Monoterpene Alcohol Linalool inArabidopsisFlowers

Jean-François Ginglinger,René Höfer,Jonathan Gershenzon,Francel Verstappen,Bernd Schneider,Laurence Miesch,Pascaline Ullmann,Tobias G Köllner,Franziska Beran,Patricia Claudel,Jérôme Mutterer,Raymonde Baltenweck,Francis Karst,Christian Paetz,Michel Miesch,Jürgen Ehlting,Raphaël Lugan ,Marc Fischer ,Benoît Boachon ,Harro J Bouwmeester ,Danièle Werck‐Reichhart

doi:10.1105/tpc.113.117382

Abstract

The cytochrome P450 family encompasses the largest family of enzymes in plant metabolism, and the functions of many of its members in Arabidopsis thaliana are still unknown. Gene coexpression analysis pointed to two P450s that were coexpressed with two monoterpene synthases in flowers and were thus predicted to be involved in monoterpenoid metabolism. We show that all four selected genes, the two terpene synthases (TPS10 and TPS14) and the two cytochrome P450s (CYP71B31 and CYP76C3), are simultaneously expressed at anthesis, mainly in upper anther filaments and in petals. Upon transient expression in Nicotiana benthamiana, the TPS enzymes colocalize in vesicular structures associated with the plastid surface, whereas the P450 proteins were detected in the endoplasmic reticulum. Whether they were expressed in Saccharomyces cerevisiae or in N. benthamiana, the TPS enzymes formed two different enantiomers of linalool: (-)-(R)-linalool for TPS10 and (+)-(S)-linalool for TPS14. Both P450 enzymes metabolize the two linalool enantiomers to form different but overlapping sets of hydroxylated or epoxidized products. These oxygenated products are not emitted into the floral headspace, but accumulate in floral tissues as further converted or conjugated metabolites. This work reveals complex linalool metabolism in Arabidopsis flowers, the ecological role of which remains to be determined.

Highlights

A prolific expansion of the cytochrome P450 (CYP) gene family in land plants has generated the largest family of enzymes in plant metabolism (Nelson and Werck-Reichhart, 2011)
By recombinant expression in yeast (Saccharomyces cerevisiae) and in planta we demonstrate that all four genes contribute to a far overlooked and complex linalool metabolism occurring in the flowers of Arabidopsis
Coexpression Analysis Identifies Candidate P450 Genes Predicted to be Involved in Monoterpenoid Metabolism

Summary

Introduction

A prolific expansion of the cytochrome P450 (CYP) gene family in land plants has generated the largest family of enzymes in plant metabolism (Nelson and Werck-Reichhart, 2011). A complex bouquet of volatile compounds, including more than 24 monoterpenes and 26 sesquiterpenes, was found emitted from inflorescences and other aerial parts of the plant (Aharoni et al, 2003; Chen et al, 2003; Steeghs et al, 2004; Rohloff and Bones, 2005). It comprised several oxygenated compounds such as the lilac aldehydes, a-terpineol, verbenone, and longiborneol. It comprised several oxygenated compounds such as the lilac aldehydes, a-terpineol, verbenone, and longiborneol. 1,8-Cineole was the main terpenoid found to be emitted from roots (Steeghs et al, 2004)

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