Anti-Tobacco Mosaic Virus Effects of Silver Nanoparticles Coated with Alginate Oligosaccharides Prepared through Enzymatic Degradation

Recombinant alginate lyase was used to degrade alginic acid to prepare unsaturated alginate oligosaccharides (AOs), which were applied to directly reduce silver nitrate to obtain AO-coated silver nanoparticles (AOs@AgNPs), and as a stabilizer as well. First, alginate lyase aly-SJ02 from the marine bacterium Pseudoalteromonas sp. SM0524 was heterologously expressed in Yarrowia lipolytica. Next, the AOs produced through enzymatic degradation were used as reducing and stabilizing agents with silver nitrate to prepare AOs@AgNPs, and the particle size, stability, and other basic data were measured. Finally, based on the enhancement of plant resistance by AOs and the broad-spectrum antiviral bactericidal effect, three kinds of AgNPs had desirable passivation, prevention, and treatment effects on tobacco mosaic virus (TMV). The best control effect was observed for AOs@AgNPs, and it has been verified that AOs@AgNPs have a strong inhibitory effect at both the gene transcription and protein expression levels of TMV. AOs@AgNPs were far better than the AgNPs prepared by using alginate polysaccharides.