Transcriptome Analysis of the Japanese Pine Sawyer Beetle, Monochamus alternatus, Infected with the Entomopathogenic Fungus Metarhizium anisopliae JEF-197.

Jong-Cheol Kim,Sihyeon Kim,Woo-Jin Kim,So-Eun Park,Tae-Young Shin,Se-Jin Lee,Jaesu Kim,Mi-Rong Lee

doi:10.3390/jof7050373

Abstract

The Japanese pine sawyer (JPS) beetle, Monochamus alternatus Hope (Coleoptera: Cerambycidae), damages pine trees and transmits the pine wilt nematode, Bursaphelenchus xylophilus Nickle. Chemical agents have been used to control JPS beetle, but due to various issues, efforts are being made to replace these chemical agents with entomopathogenic fungi. We investigated the expression of immune-related genes in JPS beetle in response to infection with JEF-197, a Metarhizium anisopliae isolate, using RNA-seq. RNA samples were obtained from JEF-197, JPS adults treated with JEF-197, and non-treated JPS adults on the 8th day after fungal treatment, and RNA-seq was performed using Illumina sequencing. JPS beetle transcriptome was assembled de novo and differentially expressed gene (DEG) analysis was performed. There were 719 and 1953 up- and downregulated unigenes upon JEF-197 infection, respectively. Upregulated contigs included genes involved in RNA transport, ribosome biogenesis in eukaryotes, spliceosome-related genes, and genes involved in immune-related signaling pathways such as the Toll and Imd pathways. Forty-two fungal DEGs related to energy and protein metabolism were upregulated, and genes involved in the stress response were also upregulated in the infected JPS beetles. Together, our results indicate that infection of JPS beetles by JEF-197 induces the expression of immune-related genes.

Highlights

The Japanese pine sawyer (JPS) beetle, Monochamus alternatus Hope (Coleoptera: Cerambycidae), is a major pest that causes serious damage to pine trees by mediating transmission of the pine wilt nematode, Bursaphelenchus xylophilus Nickle (Aphelenchida: Aphelenchoididae) that causes pine wilt disease [1]
JPS adults sprayed with a conidial suspension (1.0 × 107 conidia/mL) of JEF-197 had a mortality of 53.3% on the 8th day after fungal inoculation (Figure 1a), and the LT50 of adults was 7.86 days, which was confirmed by probit analysis (χ2 = 8.774, df = 10, p = 0.554)
Our results indicate that the immune response of JPS beetles was activated in response to fungal infection, and antimicrobial peptides (AMPs) production was likely induced

Summary

Introduction

The Japanese pine sawyer (JPS) beetle, Monochamus alternatus Hope (Coleoptera: Cerambycidae), is a major pest that causes serious damage to pine trees by mediating transmission of the pine wilt nematode, Bursaphelenchus xylophilus Nickle (Aphelenchida: Aphelenchoididae) that causes pine wilt disease [1]. This beetle has spread to East Asian countries including Korea, Japan, and China, in addition to Portugal in Europe [2,3]. The main means of controlling JPS beetles are chemical agents such as neonicotinoids, fenitrothions, thiacloprids, and thiamethoxams [4,5]. We confirmed that this fungus is highly virulent against JPS beetles [14,15]

Methods

Results

Conclusion