Isolation, Expression Profiling, and Regulation via Host Allelochemicals of 16 Glutathione S-Transferases in the Chinese White Pine Beetle, Dendroctonus armandi.

Haiming Gao,Danyang Fu,Hui Chen,Lulu Dai,Yaya Sun

doi:10.3389/fphys.2020.546592

Abstract

The Chinese white pine beetle (Dendroctonus armandi) is undoubtedly one of the most important pests causing ecological damage in the Qinling Mountains. When bark beetles invade conifers, they must overcome host tree defenses, including primary resistance and induced resistance responses. Moreover, this induced resistance occurs following herbivory by bark beetles. Bark beetles have a corresponding defense mechanism for degrading toxic compounds, and glutathione S-transferases (GSTs) can catalyze the binding of endogenous substances that reduce glutathione (GSH) to various harmful electrophilic substrates, increasing their solubility and facilitating their excretion from cells. In this experiment, we successfully obtained sixteen full-length sequences of D. armandi, which belonged to four GST categories (delta, epsilon, sigma, and theta). The transcript levels of sixteen GSTs in D. armandi were compared at four developmental stages (larvae, pupae, teneral adults, and adults), three different tissues (antennae, gut, and reproductive organs), and under various levels of terpenoid stimuli during feeding on phloem tissue to evaluate the various relevant modes of action. This study aids in the understanding of the interaction between monoterpenes and beetles, and beetles’ detoxification through GSTs.

Highlights

Bark beetles in Scolytinae, including genera Dendroctonus, Ips, and Scolytus, are the most important pests affecting forest health north of the Equator (Schelhaas et al, 2003; Raffa et al, 2008; Bentz et al, 2010; Marini et al, 2017)
Further study shows that delta and epsilon class glutathione S-transferases (GSTs) are involved in insecticide resistance in Meligethes aeneus to the most commonly used pyrethroids (Erban and Stara, 2014)
A total of 16 full-length GST codon sequences were obtained from D. armandi which belonged to the delta, epsilon, sigma, and theta families

Summary

Introduction

Bark beetles in Scolytinae, including genera Dendroctonus, Ips, and Scolytus, are the most important pests affecting forest health north of the Equator (Schelhaas et al, 2003; Raffa et al, 2008; Bentz et al, 2010; Marini et al, 2017). The Chinese white pine beetle, Dendroctonus armandi (Coleoptera: Curculionidae; Scolytinae) is one of the most harmful pests in the Qinling Mountain ecosystem (Yin et al, 1984; Chen and Yuan, 2000). Various native insects, such as D. armandi, can undergo population increases that reach epidemic levels, leading to widespread tree death in the forest ecosystem south of the Qinling Mountains. Monoterpenes are indispensable substances in pheromone precursor synthesis for beetles (Lindström et al, 1989; Seybold, 1993; Byers, 1995) or serve as the main attractant of other herbivores and even fungal symbionts (DiGuistini et al, 2011)

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