Abstract
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.
Highlights
Tobacco mosaic virus (TMV) is a plant virus used to study plant disease, and SA and JA signalling pathways have both been shown to be involved in plant defence following TMV infection
Other reports on TMV-infected tobacco, showed that the expression of genes associated with the JA-mediated defence pathway were significantly upregulated after 1 d, whereas genes associated with the SA-mediated defence pathway were significantly upregulated after 5 days
The TMV coat protein (TMV-CP) levels in inoculated leaves showed that COS could induce TMV resistance in Arabidopsis (Fig. 1)
Summary
Tobacco mosaic virus (TMV) is a plant virus used to study plant disease, and SA and JA signalling pathways have both been shown to be involved in plant defence following TMV infection. Jar[1] and NahG Arabidopsis mutants were employed to explore the signalling pathways involved in COS-induced resistance to TMV. The most effective concentration of COS, and the optimal pretreatment time, for resistance to TMV were studied in wild Arabidopsis plants.
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