DEGs in transcriptome of virulent CN-Bx1 and avirulent US-Bx1. from Enhancement of oxidative stress contributes to increased pathogenicity of the invasive pine wood nematode

Reactive oxygen species (ROS) play important roles in defence response of host plants versus pathogens. While generation and detoxification of ROS is well understood, how varied ability of different isolates of pathogens to overcome host ROS, or ROS contribution to a particular isolate's pathogenicity, remains largely unexplored. Here, we report that transcriptional regulation of ROS pathway, in combination with the insulin pathway, increases the pathogenicity of invasive species <i>Bursaphelenchus xylophilus</i>. The results showed a positive correlation between fecundity and pathogenicity of different nematode isolates. The virulent isolates from introduced populations in Japan, China and Europe had significantly higher fecundity than native avirulent isolates from the USA. Increased expression of <i>Mn-SOD</i> and reduced expression of <i>catalase</i>/<i>GPX-5</i> and H₂O₂ accumulation during invasion are associated with virulent strains. Additional H₂O₂ could improve fecundity of <i>B. xylophilus</i>. Furthermore, depletion of <i>Mn-SOD</i> decreased fecundity and virulence of <i>B. xylophilus</i>, while insulin pathway is significantly affected. Thus, we propose that destructive pathogenicity of <i>B. xylophilus</i> to pines is partly due to upregulated fecundity modulated by insulin pathway in association with ROS pathway and further enhanced by H₂O₂ oxidative stress. These findings provide a better understanding of pathogenic mechanisms in plant–pathogen interactions and adaptive evolution of invasive species.This article is part of the theme issue ‘Biotic signalling sheds light on smart pest management’.

活性氧簇（Reactive oxygen species，ROS）在宿主植物对抗病原菌的防御反应中发挥关键作用。尽管ROS的产生与解毒机制已被充分阐明，但不同病原菌分离株克服宿主ROS的能力存在差异，且ROS对特定分离株致病性的贡献仍未得到充分探索。本研究发现，ROS通路与胰岛素通路的转录调控协同作用，可提升入侵物种松材线虫（Bursaphelenchus xylophilus）的致病性。研究结果显示，不同线虫分离株的繁殖力与致病性呈正相关。采自日本、中国及欧洲入侵种群的强毒性分离株，其繁殖力显著高于来自美国的本土无毒分离株。入侵过程中，锰超氧化物歧化酶（Mn-SOD）的表达上调、过氧化氢酶（catalase）/谷胱甘肽过氧化物酶5（GPX-5）的表达下调，以及过氧化氢（H₂O₂）的积累，均与强毒株相关。外源过氧化氢（H₂O₂）可提升松材线虫的繁殖力。此外，敲低锰超氧化物歧化酶（Mn-SOD）的表达会降低松材线虫的繁殖力与毒性，同时胰岛素通路也会受到显著影响。据此，我们提出：松材线虫对松树的破坏性致病性，部分源于胰岛素通路与ROS通路协同调控的繁殖力上调，且该过程可被过氧化氢（H₂O₂）介导的氧化应激进一步增强。本研究结果有助于深入理解植物-病原菌互作的致病机制，以及入侵物种的适应性进化。本文隶属于“生物信号传导为智能害虫防治提供启示”专题栏目。