Evolution of Terpene Synthases in Orchidaceae.

Li-Min Huang,Wen-Huei Chen,Chun-Neng Wang,Hsin Huang,Hong-Hwa Chen,Yu-Chen Chuang

doi:10.3390/ijms22136947

Abstract

Terpenoids are the largest class of plant secondary metabolites and are one of the major emitted volatile compounds released to the atmosphere. They have functions of attracting pollinators or defense function, insecticidal properties, and are even used as pharmaceutical agents. Because of the importance of terpenoids, an increasing number of plants are required to investigate the function and evolution of terpene synthases (TPSs) that are the key enzymes in terpenoids biosynthesis. Orchidacea, containing more than 800 genera and 28,000 species, is one of the largest and most diverse families of flowering plants, and is widely distributed. Here, the diversification of the TPSs evolution in Orchidaceae is revealed. A characterization and phylogeny of TPSs from four different species with whole genome sequences is available. Phylogenetic analysis of orchid TPSs indicates these genes are divided into TPS-a, -b, -e/f, and g subfamilies, and their duplicated copies are increased in derived orchid species compared to that in the early divergence orchid, A. shenzhenica. The large increase of both TPS-a and TPS-b copies can probably be attributed to the pro-duction of different volatile compounds for attracting pollinators or generating chemical defenses in derived orchid lineages; while the duplications of TPS-g and TPS-e/f copies occurred in a species-dependent manner.

Highlights

Terpenoids are the largest group of natural metabolites in the plant kingdom, including more than 40,000 different compounds, and have multiple physiological and ecological roles
Some terpene synthases (TPSs) are responsible for producing compounds that are related to plant growth and development, such as gibberellin biosynthesis [29], others are responsible in secondary metabolism like monoterpenes and sesquiterpenes for pollination and defense [30,31]
There are two compartmentalized terpenoid biosynthesis pathways, the mevalonic acid (MVA) pathway that occurs in the cytosol, and the methylerythritol phosphate (MEP) pathway that occurs in plastids to produce isopentenyl diphosphate (IPP) and its allylic isomer-dimethylallyl diphosphate (DMAPP) converted by isopentenyl diphosphate isomerase (IDI) (Figure 1) [50,51,52]

Summary

Introduction

Terpenoids are the largest group of natural metabolites in the plant kingdom, including more than 40,000 different compounds, and have multiple physiological and ecological roles. Most terpene synthases belong to monoterpene synthase (MTPSs) [22], sesquiterpene synthase (STPSs), and diterpene synthase (DTPSs) [23] They all share three conserved domains in the active site, including ‘DDXXD’, ‘DXDD’, and ‘EDXXD’. Some TPSs are responsible for producing compounds that are related to plant growth and development, such as gibberellin biosynthesis [29], others are responsible in secondary metabolism like monoterpenes and sesquiterpenes for pollination and defense [30,31]. Containing more than 800 genera and 28,000 species, the Orchidaceae, classified in class Liliopsida, order Asparagales, is one of the largest and most diverse families of flowering plants [33].

Terpenoids and Their Biosynthesis in Plants

The Arrangement of TPS

Conclusions