Metarhizium anisopliae JEF-197 Loses Glucose Metabolism in Surviving Japanese Pine Sawyer Beetle Against the Fungal Pathogen

Abstract

Japanese pine sawyer beetle (JPSB), Monochamus alternatus is a forest insect pest with damaging to pine trees through vectoring plant-parasitic nematodes. In our previous work, the entomopathogenic Metarhizium anisopliae JEF-197 was effective in controlling JPSB adults. However some of JPSB adults survived well even against the fungal treatment. Now here in this work, we analyzed the transcriptome of JEF-197 from the fungus-treated JPSB adults which still survived in 8 days after the treatment. The day was determined based on the lethal time 50 (LT₅₀) in our previous study. As a control, JEF-197 was cultured on 1/4SDA for 8 days. The plate-cultured JEF-197 transcripts were used for building-up an index in the abundance analysis using kallisto to investigate the gene regulation. Additionally, transcripts from the JEF-197-treated PSB were analyzed to find possible fungal transcripts to enlarge the index of abundance analysis. In the following differentially expressed gene (DEG) analysis, most JEF-197 transcripts showed significant down-regulations in JPSB adults 8 days after treatment, which were presented as clustering heatmap, PCA, MA and Volcano plots. The GO enrichment analysis showed similar results, in which most of pathways were significantly suppressed. Metabolic and biosynthesis metabolisms were most dominantly downregulated pathways. Particularly, many genes of glucose metabolisms were significantly suppressed, including genes for glycolysis, TCA, ATP & nucleotide synthesis, and glycogen & chitin production. This work suggests that JEF-197 lost its own glucose metabolism in the survived JPSB adults, and the survival could be involved in the active and continuous host defense mechanisms. It gives us questions what factors would be involved in the different response of individual to the fungal treatment and what happens if live and dead hosts were pooled in RNA-sequencing.