Comparative transcriptomic analysis of the regulatory mechanisms underlying the resistance to Fusarium foetens mediated by konjac glucomannan oligosaccharides in tobacco

Oligosaccharides derived from storage polysaccharides have shown considerable potential in boosting innate immunity. In this study, konjac glucomannan oligosaccharides (KGMOS) with degree of polymerization 2–13 obtained by enzymatic hydrolysis of storage konjac glucomannans (KGM), was employed against the harmful pathogen Fusarium foetens in Nicotiana benthamiana. The application of KGMOS at concentrations ranging from 0.025 to 0.1 mg mL⁻¹ significantly inhibited the pathogen, reduced disease severity, and markedly increased the levels of H₂O₂ and callose. Comparative transcriptomic analysis revealed that distinct DEGs in KGMOS-treated plants were involved in MAPK signaling, plant hormone signal transduction, and plant-pathogen interaction pathways. Notably, defense-related genes associated with salicylic acid (SA) and jasmonic acid/ethylene (JA/ET) pathways were upregulated. Analysis indicates that the levels of transcripts encoding PR1, PR2, PR5 and NPR1 were increased in plants treated with KGMOS. Meanwhile, transcription factors, enzymes, receptors and co-receptors associated with defense responses were also upregulated in KGMOS treatment. RT-qPCR further confirmed the significant upregulation of SA and JA/ET pathway genes in KGMOS-treated plants. Increased SA content (2.37-fold) in these plants suggests improved disease resistance. The study concludes that KGMOS effectively enhances resistance against F. foetens, with high efficiency at 0.025 mg mL⁻¹, the lowest concentration assayed. These findings provided valuable insights into the potential application of KGMOS for disease management in sustainable agriculture and postharvest scenarios.