Plant immune inducers are crucial tools for the green management of crop diseases. As an environmentally friendly biological inducer, oligochitosan (COS) can activate plant defense mechanisms to resist pathogens such as fungi, bacteria, and viruses. However, previous studies have mostly focused on its effects against tobacco mosaic virus, and the resistance mechanism against potato virus Y (PVY) remains unclear. PVY is a highly destructive virus that causes significant yield losses in potatoes and tobacco crops in developing countries. This gap has restricted the application of COS in PVY control. So, how exactly does COS induce plants to develop PVY resistance?
A research team led by Academician Baoan Song from the State Key Laboratory of Green Pesticide at Guizhou University conducted a systematic study using Nicotiana benthamiana as the model plant. The related findings have been published in Frontiers of Agricultural Science and Engineering (DOI: 10.15302/J-FASE-2025666).
Results showed that COS at a concentration of 100 μg·mL^–1 achieved a preventive efficacy of 54.7% against PVY, significantly reducing virus-induced damage to plants. Biochemical analyses revealed that COS treatment enhanced the activities of defense-related enzymes including catalase (CAT), peroxidase (POD), phenylalanine ammonia-lyase (PAL), and superoxide dismutase (SOD), while increasing hydrogen peroxide (H₂O₂) content—changes that collectively strengthen plant defense capabilities.
Integrated transcriptomic and proteomic analyses further uncovered the underlying molecular mechanisms: COS treatment induced differential expression of key genes (e.g., OXI1, NDPK4, MAPKKK21) and proteins associated with reactive oxygen species (ROS) signaling and the mitogen-activated protein kinase (MAPK) pathway in N. benthamiana. Functional validation demonstrated that COS specifically upregulates OXI1 gene expression, which in turn promotes the expression of MAPKKK21 and NDPK4, activating the MAPK signaling cascade and thereby enhancing PVY resistance.
To confirm the core role of OXI1, experiments were conducted using OXI1-overexpressing and OXI1-RNAi N. benthamiana mutants. Results indicated that plants overexpressing OXI1 exhibited significantly milder symptoms after PVY infection, with a 40% reduction in the expression of the PVY coat protein (PVY-CP). In contrast, OXI1-silenced plants were more susceptible to PVY, showing a 112% increase in PVY-CP expression. These findings clearly demonstrate that OXI1 is a key molecule mediating COS-induced PVY resistance.
This study clarifies that COS induces plant resistance against PVY through the ROS-mediated MAPK signaling pathway, filling the existing research gap. The discovery provides an important theoretical basis for the development of efficient and environmentally friendly plant antiviral agents, holding great promise for advancing the green control of PVY, reducing chemical pesticide use, and safeguarding the yield security of crops such as potatoes and tobacco.