# Effects of Dominant Associated Bacteria Agrobacterium radiobacter Bx.F4 and Delftia tsuruhatensis Bx.Q2 on the Physiological Traits of Bursaphelenchus xylophilus: Insights from RNA-Seq Analysis

## TL;DR

This study shows how two bacteria associated with pine wood nematodes affect their movement, reproduction, and disease-causing ability.

## Contribution

The study identifies specific bacterial strains that influence nematode physiology and pathogenicity through RNA-Seq analysis.

## Key findings

- Agrobacterium radiobacter Bx.F4 enhances nematode motility, reproduction, and pathogenicity.
- Delftia tsuruhatensis Bx.Q2 reduces nematode motility, reproduction, and pathogenicity.
- RNA-Seq analysis revealed enriched pathways like JNK, Wnt, and FOXO related to nematode physiology.

## Abstract

To investigate the role of bacteria associated with pine wood nematodes (PWNs), Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle, we isolated two dominant bacterial strains (Agrobacterium radiobacter Bx.F4 and Delftia tsuruhatensis Bx.Q2) from B. xylophilus with different pathogenicity (highly pathogenic F and weakly pathogenic Q) identified in previous studies. In this study, Agrobacterium radiobacter Bx.F4 and Delftia tsuruhatensis Bx.Q2 were inoculated, respectively, to aseptic PWNs to identify the effects of dominant nematode-associated bacteria on the motility, egg laying, population growth, lifespan, feeding ability, and pathogenicity of PWNs. The results showed that Agrobacterium radiobacter Bx.F4 could significantly enhance the motility, egg-laying, population growth, lifespan, feeding ability, and pathogenicity of PWNs, while Delftia tsuruhatensis Bx.Q2 exhibited the opposite effects. Furthermore, using RNA-sequencing analysis, we found that the longevity regulatory pathways, along with the JNK, Wnt, and FOXO signaling pathways related to these genes were clearly enriched. These results indicate that dominant bacterial strains associated with B. xylophilus may regulate various metabolic activities within the nematode, thereby exerting a significant influence on its physiological state and pathogenicity. This also provides a potential strategy for the biocontrol of pine wilt disease (PWD).