Wu_2026_Front.Microbiol_17_1894528

INTRODUCTION: Strigolactones (SLs) are carotenoid-derived signaling molecules that play essential roles in plant development and rhizosphere communication, particularly in the establishment of beneficial plant-fungus interactions. Although SL-mediated signaling has been extensively studied in arbuscular mycorrhizal symbioses, its role in the Gastrodia elata-Armillaria association remains largely unknown. METHODS: In this study, the Gastrodia-symbiotic strain Armillaria gallica Arm016 and the non-symbiotic strain Armillaria ostoyae Arm024 were used to investigate the effects of the synthetic SL analog GR24 on fungal growth, rhizomorph development, and transcriptional responses. To explore the molecular basis of SL perception, three candidate receptor-encoding transcripts were identified in Arm016 through homology-based screening. Domain annotation and structural modeling were performed to characterize their structural features. RESULTS: GR24 treatment significantly promoted rhizomorph formation in Arm016, increasing rhizomorph numbers by 82.9% compared with the control (p < 0.01), whereas only a minor effect was observed in Arm024. Biomass accumulation was enhanced in both strains following GR24 treatment. Transcriptome analysis revealed markedly different responses between the two species. A total of 489 differentially expressed genes (DEGs) were identified in Arm016, compared with only 55 DEGs in Arm024. Functional enrichment analysis indicated that GR24-responsive genes in Arm016 were primarily associated with filamentous growth, metabolic processes, catalytic activity, and transporter functions, suggesting extensive transcriptional reprogramming related to fungal development. In contrast, Arm024 exhibited a comparatively weak transcriptional response. Domain annotation revealed the presence of the conserved alpha/beta-hydrolase (Abhydrolase_1) domain, a hallmark of canonical plant SL receptors. Structural modeling further demonstrated that the candidate protein i2 shares a conserved alpha/beta-hydrolase fold with the Arabidopsis thaliana SL receptor D14 (TM-score = 0.64), supporting its potential role in SL perception. DISCUSSION/CONCLUSION: Collectively, these findings demonstrate that symbiotic and non-symbiotic Armillaria species exhibit distinct sensitivities to SL signaling and provide preliminary evidence for the existence of D14/KAI2-like SL perception mechanisms in Armillaria. This study advances our understanding of chemical communication within the Gastrodia-Armillaria symbiosis and provides a foundation for elucidating the molecular mechanisms underlying fungal recruitment and symbiotic establishment.