Molecular Cloning and Characterization of Five Glutathione S-Transferase Genes and Promoters from Micromelalopha troglodyta (Graeser) (Lepidoptera: Notodontidae) and Their Response to Tannic Acid Stress.

Fang Tang,Huizhen Tu,Xiwu Gao,Pei Liang,Qingli Shang

doi:10.3390/insects11060339

Fang Tang, Huizhen Tu + Show 3 more

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https://doi.org/10.3390/insects11060339

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Abstract

Plants accumulate phenolic compounds such as tannic acid to resist insect herbivores. The survival of insects exposed to toxic secondary metabolites depends on the detoxification metabolism mediated by limited groups of glutathione S-transferases (GSTs). Micromelalopha troglodyta (Graeser) (Lepidoptera: Notodontidae) is an important foliar pest of poplar trees. GSTs play an important role in xenobiotic detoxification in M. troglodyta. Five GST genes were identified in M. troglodyta and were classified into five different cytosolic GST classes, delta, omega, sigma, theta, and zeta. Real-time fluorescent quantitative polymerase chain reaction (qPCR) was used to determine the mRNA expression of the five cloned GSTs in the midguts and fat bodies of M. troglodyta. The mRNA expression of the five GSTs was significantly induced when M. troglodyta was exposed to tannic acid. To further understand the tannic acid regulatory cascade, the 5′-flanking promoter sequences of the five MtGSTs were isolated by genome walking methods, and the promoters were very active and induced by tannic acid. In summary, the induction of GST mRNA expression was due to the response of five MtGST promoters to tannic acid. Therefore, MtGST promoters play an important role in the regulation of GST transcription.

Highlights

The rapid growth and spread of the poplar tree account for its widespread cultivation and naturalization throughout the world
We address the following questions in this study: (1) How does tannic acid affect the expression of MtGST mRNA and (2) how do the 5 MtGST promoters respond to tannic acid? These studies are very important in understanding the regulatory mechanism of MtGST mRNA expression in M. troglodyta
MtGSTt1 was induced by tannic acid, while the transcriptional expression of MtGSTt1 was inhibited, which showed that in addition to the promoter, there may be negative regulatory elements involved in the expression of MtGSTt1 in M. troglodyta

Summary

Introduction

The rapid growth and spread of the poplar tree account for its widespread cultivation and naturalization throughout the world. The wood is commonly used as fuel, but is used for furniture, panelling and plywood production [1]. Poplar trees are vital to the forests of China, and Micromelalopha troglodyta (Graeser) (Lepidoptera: Notodontidae) is an important foliar pest of poplar trees. Due to the high fecundity and rapid growth of this insect, infestations usually lead to huge economic losses. Because of many kinds of plant secondary metabolites in poplars [1], the host chemical defence was the main pressure for these pests in addition to the pesticide stress. Detoxification enzymes, including glutathione S-transferases (GSTs; EC2.5.1.18), are important parts of adaptation mechanisms. GSTs act in physiological roles by initiating the detoxication of potential alkylating agents and interacting

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