AUTHOR=Shen Zhong-Jian , Liu Yan-Jun , Gao Xu-Hui , Liu Xiao-Ming , Zhang Song-Dou , Li Zhen , Zhang Qing-Wen , Liu Xiao-Xia 

TITLE=Molecular Identification of Two Thioredoxin Genes From Grapholita molesta and Their Function in Resistance to Emamectin Benzoate

JOURNAL=Frontiers in Physiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2018.01421

DOI=10.3389/fphys.2018.01421

ISSN=1664-042X

ABSTRACT=<p>Thioredoxins (Trxs), a member of the thioredoxin system, play crucial roles in maintaining intracellular redox homeostasis and protecting organisms against oxidative stress. In this study, we cloned and characterized two genes, <italic>GmTrx2</italic> and <italic>GmTrx-like1</italic>, from <italic>Grapholita molesta</italic>. Sequence analysis showed that <italic>GmTrx2</italic> and <italic>GmTrx-like1</italic> had highly conserved active sites CGPC and CXXC motif, respectively, and shared high sequence identity with selected insect species. The quantitative real-time polymerase chain reaction results revealed that <italic>GmTrx2</italic> was mainly detected at first instar, whereas <italic>GmTrx-like1</italic> was highly concentrated at prepupa day. The transcripts of <italic>GmTrx2</italic> and <italic>GmTrx-like1</italic> were both highly expressed in the head and salivary glands. The expression levels of <italic>GmTrx2</italic> and <italic>GmTrx-like1</italic> were induced by low or high temperature, <italic>E. coli</italic>, <italic>M. anisopliae</italic>, H<sub>2</sub>O<sub>2</sub>, and pesticides (emamectin benzoate). We further detected interference efficiency of <italic>GmTrx2</italic> and <italic>GmTrx-like1</italic> in <italic>G. molesta</italic> larvae and found that peroxidase capacity, hydrogen peroxide content, and ascorbate content all increased after knockdown of <italic>GmTrx2</italic> or <italic>GmTrx-like1</italic>. Furthermore, the hydrogen peroxide concentration was increased by emamectin benzoate and the sensitivity for larvae to emamectin benzoate was improved after <italic>GmTrx2</italic> or <italic>GmTrx-like1</italic> was silenced. Our results indicated that <italic>GmTrx2</italic> and <italic>GmTrx-like1</italic> played vital roles in protecting <italic>G. molesta</italic> against oxidative damage and also provided the theoretical basis for understanding the antioxidant defense mechanisms of the Trx system in insects.</p>