Chitosan Oligosaccharide
Antiviral activity of chitosan nanoparticles for controlling plant-infecting viruses
Chitosan nanoparticles (ChiNPs) are a potentially effective means for controlling numerous plant diseases. This study firstly describes the antiviral capabilities of ChiNPs to control plant viral diseases compared to its bulk form. Bean yellow mosaic virus (BYMV) was used as a model plant virus affecting faba bean plants and many other legumes. The antiviral effectiveness of ChiNPs and chitosan were evaluated as a curative application method, using six dosage rates (50, 100, 200, 250, 300 and 400 mg/L). Results indicated that ChiNPs curatively applied 48 h post virus inoculation entirely inhibit the disease infectivity and viral accumulation content at 300 mg/L and 400 mg/L. The virus titre was greatly alleviated within the plant tissues by 7.71% up to100% depending on ChiNP dosage rates. However, chitosan used in its bulk-based material form revealed a relatively low to an intermediate reduction in virus infectivity by 6.67% up to 48.86%. Interestingly, ChiNPs affect the virus particle’s integrity by producing defective and incomplete BYMV viral particles, defeating their replication and accumulation content within the plant tissues. Simultaneously, ChiNP applications were appreciably shown to promote the pathogenesis-related (PR-1) gene and other defence-related factors. The mRNA of the PR-1 gene was markedly accumulated in treated plants, reaching its maximum at 400 mg/L with 16.22-fold relative expression change over the untreated control. Further, the total phenol dynamic curve was remarkably promoted for 30 days in response to ChiNP application, as compared to the untreated control. Our results provide the first report that chitosan-based nanomaterials have a superior effect in controlling plant viruses as an antiviral curing agent, suggesting that they may feasibly be involved in viral disease management strategies under field conditions without serious health concerns and environmental costs.
Significance: Our findings show that chitosan nanoparticles have a powerful curing antiviral activity against BYMV disease. These findings open the door for the use of eco-friendly nano-based tools in controlling numerous plant viruses. The use of eco-friendly nano-based materials could result in a successful integrative control strategy for plant viruses under field conditions, negating the need for the conventional measure used to control most of the insect-transmitted plant viruses, that is insecticide application against vector insects.
Chitosan is one of the most abundant carbohydrate biopolymers in the world and chitosan oligosaccharide (COS), which is prepared from chitosan, is a plant immunity regulator. The present study aimed to validate the effect of COS on inducing resistance to tobacco mosaic virus (TMV) in Arabidopsis and to investigate the potential defence-related signalling pathways involved. Optimal conditions for the induction of TMV resistance in Arabidopsis were COS pretreatment at 50 mg/L for 1 day prior to inoculation with TMV. Multilevel indices, including phenotype data and TMV coat protein expression, revealed that COS induced TMV resistance in wild-type and jasmonic acid pathway- deficient (jar1) Arabidopsis plants, but not in salicylic acid pathway deficient (NahG) Arabidopsis plants. Quantitative-PCR and analysis of phytohormone levels confirmed that COS pretreatment enhanced the expression of the defence-related gene PR1, which is a marker of salicylic acid signalling pathway and increased the amount of salicylic acid in WT and jar1, but not in NahG plants. Taken together, these results confirm that COS induces TMV resistance in Arabidopsis via activation of the salicylic acid signalling pathway.
Cucumber mosaic virus (CMV), one of the main viruses, is responsible for Passiflora spp. (passion fruit) virus diseases, which negatively affect its planting, cultivation, and commercial quality. In this study, a laboratory anti-CMV activity screening model for Passiflora spp. CMV disease was first established. Then, the effects of different antiviral agents of chitosan oligosaccharide (COS), dufulin (DFL), and ningnanmycin (Ning) on CMV virulence rate in Passiflora spp. were determined. The virulence rate and anti-CMV activity in Passiflora spp. treated with COS were 50% and 45.48%, respectively, which were even better than those of DFL (66.67% and 27.30%, respectively) and Ning (83.30% and 9.17%, respectively). Field trials test results showed COS revealed better average control efficiency (47.35%) against Passiflora spp. CMV disease than those of DFL (40.93%) and Ning (33.82%), indicating that COS is effective in the control of the Passiflora spp. CMV disease. Meanwhile, the nutritional quality test results showed that COS could increase the contents of soluble solids, titratable acids, vitamin C, and soluble proteins in Passiflora spp. fruits as well as enhance the polyphenol oxidase (PPO), superoxide dismutase (SOD), and peroxidase (POD) activity in the leaves of Passiflora spp. seedlings. In addition, the combined transcriptome and proteome analysis results showed that COS mainly acted on the Brassinosteroids (BRs) cell signaling pathway, one of plant hormone signal transduction pathway, in Passiflora spp., thus activating the up-regulated expression of TCH4 and CYCD3 genes to improve the resistance to CMV disease. Therefore, our study results demonstrated that COS could be used as a potential plant immune inducer to control the Passiflora spp. CMV disease in the future.