Physicochemically distinct gold nanomaterials suppress pine wilt disease through divergent nematicidal mechanisms against Bursaphelenchus xylophilus

Pine wilt disease (PWD), caused by Bursaphelenchus xylophilus , is notoriously difficult to control as the nematodes reside deep within host tissues, while conventional chemical treatments pose significant ecological risks. This study reports on the synthesis, characterization, and comparative evaluation of two distinct, environmentally friendly gold nanomaterials for PWD management: ultrasmall, negatively charged L-histidine-stabilized gold nanoclusters (His-AuNCs) and larger, positively charged polyethyleneimine-functionalized gold nanoparticles (PEI-AuNPs). His-AuNCs were synthesized via a green aqueous-phase method, yielding monodisperse particles (1.36 ± 0.05 nm; -19.2 ± 0.3 mV). PEI-AuNPs were uniform, spherical particles with a positive surface charge (+26.5 ± 1.5 mV) and a hydrodynamic diameter of 11.18 ± 0.9 nm. In vitro assays demonstrated that both nanomaterials induced nematode immobilization in a concentration- and time-dependent manner, with 0.5 mg/L His-AuNCs causing ~70% immobility and 0.5 mg/L PEI-AuNPs causing over 75% immobility after 48 hours. In feeding-based assays, both materials suppressed nematode population expansion. Confocal and TEM imaging confirmed that both nanoparticles were internalized by B. xylophilus , accumulating in internal tissues, particularly in the anterior and intestinal regions. Stem injection of either nanomaterial (at 0.05 mg/L) effectively delayed symptom onset, reduced disease severity, and preserved vascular integrity in pine seedlings. Transcriptomic analysis revealed distinct molecular responses: His-AuNCs downregulated genes related to cuticle formation and metabolism, whereas PEI-AuNPs induced a focused stress response, primarily upregulating heat shock proteins. Despite their potent bioactivity, both materials exhibited minimal acute toxicity in zebrafish assays, supporting their environmental safety. These findings establish that surface functionalization is associated with distinct phenotypic and transcriptional response signatures of gold nanomaterials and demonstrate that both PEI-AuNPs and His-AuNCs are promising, dual-function agents for the sustainable control of pine wilt disease. • Surface-functionalized gold nanomaterials directly suppress Bursaphelenchus xylophilus • Ultrasmall Au nanoclusters and PEI-Au nanoparticles show distinct nematicidal modes • Gold nanomaterials are internalized and accumulate in nematode tissues • Low-dose stem injection delays pine wilt disease and preserves vascular integrity • Minimal acute toxicity is observed in a zebrafish biosafety model