Structural characterization of a polysaccharide from dry mycelium of Penicillium chrysogenum that induces resistance to Tobacco mosaic virus in tobacco plants.

Polysaccharides are essential macromolecules that are present in all living organisms. They have a range of biological activities, such as antiviral, antioxidant, immunity-enhancing, and anticancer activities. In this study, a polysaccharide (PCPS) was separated and extracted from dry mycelium of Penicillium chrysogenum by a boiling water step and gel-filtration chromatography. Its structure was characterized by high performance gel-permeation chromatography, chemical derivative, and nuclear magnetic resonance analyses. The results showed that PCPS is a neutral galactomannan with an apparent molecular weight of 19.5 kDa. We evaluated the antiviral activity of PCPS. In half-leaf assays of tobacco plants, the protective effect of PCPS against Tobacco mosaic virus (TMV) was stronger than the protective effects of ningnanmycin and oligosaccharins. Electron microscopy analyses showed that PCPS can directly inactivate viral particles. The mechanism of the antiviral activity of PCPS was explored in a preliminary study. PCPS induced the production of NO and H₂O₂ to initiate an early defense response. Treatment with PCPS resulted in increased transcript levels of the genes PAL, 4CL, LPO, and increased activities of phenylalanine lyase and peroxidase, which improved the TMV resistance of Nicotiana glutinosa. Expression of the PR-1b gene was also activated during the defense response.