Up-regulation of carbon metabolism-related glyoxylate cycle and toxin production in Beauveria bassiana JEF-007 during infection of bean bug, Riptortus pedestris (Hemiptera: Alydidae)

• RNA-Seq of Bb JEF-007-infected bean bugs was conducted to identify highly expressed genes.
• Fungal glyoxylate cycle-related genes were highly expressed in the JEF-007-infected bean bugs.
• This work provides insight into how B. bassiana grow in bean bug at late stage infection.

Beauveria bassiana (Bb) is used as an environment-friendly biopesticide. However, the molecular mechanisms of Bb-host interactions are not well understood. Herein, RNA isolated from B. bassiana (Bb JEF-007) and Riptortus pedestris (Hemiptera: Alydidae) infected with this strain were firstly subjected to high-throughput next generation sequencing (NGS) to analyze and compare transcriptomes. Due to lack of fungal and host genome information, fungal transcriptome was processed to partially exclude non-infection specific genes and host-flora. Differentially Expressed Gene (DEG) analysis showed that 2381 genes were up-regulated and 2303 genes were down-regulated upon infection. Most DEGs were classified into the categories of single-organism, cellular and metabolism processes by Gene Ontology analysis. Most DEGs were involved in metabolic pathways based on Kyoto Encyclopedia of Genes and Genomes pathway mapping. Carbon metabolism-related enzymes in the glyoxylate cycle were significantly up-regulated, suggesting a possible role for them in Bb growth in the host. Additionally, transcript levels of several fungal genes were dramatically increased after infection, such as cytotoxic lectin-like protein, bacterial-like toxin, proteins related to cell wall formation, hyphal growth, nutrient uptake, and halogenated compound synthesis. This work provides insight into how entomopathogenic B. bassiana grows in agriculturally harmful bean bug at 6 d post infection.