CSL-gel induces broad-spectrum resistance against different plant virus
To assess whether CSL-gel induces broad-spectrum resistance against different virus, N. benthamiana plants treated with CSL-gel were separately inoculated with the tobacco rattle virus (TRV), potato virus X (PVX) and turnip mosaic virus (TuMV) by rubbing. SL-gel and water treated plants were included as controls. At the early stage of infection (TRV: 5 dpi, TuMV: 12dpi), the number of green fluorescent spots in CSL-gel-treatedN. benthamiana was similar to SL-gel-treated plants. However, in the late stage of infection (TRV: 9 dpi, TuMV: 16 dpi), the green fluorescent signals present in the young leaves of the CSL-gel-treated plant were significantly lower than that of the water and SL-gel treatment groups (Figure 6a-b ). Figure 6c showed that 18 days after inoculation, symptoms caused by PVX were relatively mild in the young leaves of and CSL-gel-treated plants, while PVX caused severe symptoms in the young leaves of water-treated plants. At 22 dpi, PVX infection developed severely curly young leaves in the water-treated plants, and plants treated with SL-gel showed mild symptoms. However, no symptoms caused by PVX infection were observed in the CSL-gel-treated plants (Figure 6c ). Furthermore, qPCR analysis showed that the number of virus-CP transcripts in the CSL-gel-treated plant was significantly lower than that in the SL-gel and water-treated plants (Figure 6d-i ). Therefore, we can conclude that CSL-gel inhibits the infection caused by the majority of viruses in N. benthamianaplants.