Antiviral effect of the cotton plant-derived gossypol against tomato yellow leaf curl virus

Current approaches to controlling plant viral diseases mainly focus on plant resistance, whereas suppression of viruses in vector species could provide an important alternative approach. Here we identified the therapeutic compound, gossypol, as capable of clearing Tomato yellow leaf curl virus (TYLCV) from its vector Bemisia tabaci (whitefly). Our initial field surveys showed that no whiteflies identified from cotton carried TYLCV, in contrast to a high incidence of this virus in whiteflies from other crops including tomato, cucumber and sweet potato. We found that when whiteflies were transferred from tomato or cucumber to cotton, there was a sharp reduction in the number of viruliferous whiteflies. When the whiteflies fed on cotton or ingested the metabolite, gossypol, derived from cotton, there was a sharp decrease in the incidence and abundance of TYLCV carried by the whiteflies. Gossypol degraded the coat protein and viral genome of TYLCV both in vitro and in vivo. Laboratory and field trials all showed that gossypol decreased TYLCV disease severity and had therapeutic efficacy on the disease. Our findings point to the possibility of identifying virus-therapeutic compounds by initially screening viruses in vectors derived from different crop plants.