Identification of a Dolabellane Type Diterpene Synthase and other Root-Expressed Diterpene Synthases in Arabidopsis.

Qiang Wang,Reuben J Peters,Andrew Muchlinski,Jung-Hyun Huh,Dorothea Tholl,Meirong Jia

doi:10.3389/fpls.2016.01761

Qiang Wang, Reuben J Peters + Show 4 more

Open Access

https://doi.org/10.3389/fpls.2016.01761

Copy DOI

Abstract

Arabidopsis thaliana maintains a complex metabolism for the production of secondary or specialized metabolites. Such metabolites include volatile and semivolatile terpenes, which have been associated with direct and indirect defensive activities in flowers and leaves. In comparison, the structural diversity and function of terpenes in Arabidopsis roots has remained largely unexplored despite a substantial number of root-expressed genes in the Arabidopsis terpene synthase (TPS) gene family. We show that five root-expressed TPSs of an expanded subfamily-a type clade in the Arabidopsis TPS family function as class I diterpene synthases that predominantly convert geranylgeranyl diphosphate (GGPP) to different semi-volatile diterpene products, which are in part detectable at low levels in the ecotypes Columbia (Col) and Cape Verde Island (Cvi). The enzyme TPS20 produces a macrocyclic dolabellane diterpene alcohol and a dolabellane-related diterpene olefin named dolathaliatriene with a so far unknown C6-C11 bicyclic scaffold besides several minor olefin products. The TPS20 compounds occur in all tissues of Cvi but are absent in the Col ecotype because of deletion and substitution mutations in the Col TPS20 sequence. The primary TPS20 diterpene products retard the growth of the root rot pathogen Pythium irregulare but only at concentrations exceeding those in planta. Together, our results demonstrate that divergence and pseudogenization in the Arabidopsis TPS gene family allow for structural plasticity in diterpene profiles of above- and belowground tissues.

Highlights

Among the many specialized metabolites that are synthesized by plants, terpenes exhibit some of the highest biosynthetic and structural diversity (Degenhardt et al, 2009; Thimmappa et al, 2014; Zi et al, 2014; Lange, 2015; Tholl, 2015)
While sesquiTPS and/or diterpene synthases (diTPSs) activities were detected for Col TPS9, TPS22, TPS25, TPS26, and TPS30, no activity was found for the full length or truncated recombinant proteins of TPS19, TPS20, and TPS29 in coexpression with (E,E)-FPP synthase, geranylgeranyl diphosphate (GGPP) synthase, or entCPP synthase
We found that TPS20 was expressed in roots of the ecotype Cape Verde Island (Cvi), whereas transcripts of TPS19 and TPS29 were not detected in the root of this ecotype (Supplementary Figure S1)

Summary

Introduction

Among the many specialized metabolites that are synthesized by plants, terpenes exhibit some of the highest biosynthetic and structural diversity (Degenhardt et al, 2009; Thimmappa et al, 2014; Zi et al, 2014; Lange, 2015; Tholl, 2015). This diversity is reflective of the multiple biological roles of terpene compounds in the attraction of pollinators (Byers et al, 2014), in direct and indirect defense against herbivores and pathogens (Kessler and Baldwin, 2001; Unsicker et al, 2009; Hall et al, 2011; Schmelz et al, 2011; Huang et al, 2012; Mithöfer and Boland, 2012; Quintana-Rodriguez et al, 2015), as signals in systemic acquired resistance or inter/intra-plant communication (Arimura et al, 2000; Heil and Silva Bueno, 2007; Karban and Shiojiri, 2009; Chaturvedi et al, 2012), and in the protection against abiotic stress (Loreto et al, 2001; Ryan et al, 2014; Vaughan et al, 2015) To facilitate such interactions at short and long distance, plants often employ volatile or Diterpene Synthases in Arabidopsis semi-volatile terpenes of low molecular weight that include the 5-carbon hemiterpenes, 10-carbon monoterpenes, 15-carbon sesquiterpenes, and 20-carbon diterpenes (Dudareva et al, 2006). Comparatively few studies have shown to what extent the diversity of volatile or semi-volatile terpene metabolism and function in plant roots resembles that of leaves and flowers or varies depending on the exposure of plant tissues to different environments above and belowground (Köllner et al, 2008; Chen et al, 2009)

Methods

Results

Conclusion