Quercetin influences response in Nicotiana megalosiphon infected by satellite-associated cucumber mosaic virus

Quercetin is a prominent flavonoid with a remarkable spectrum of biochemical activities. Its impact on human health, as well as its role in the normal development of plants has been exten-sively studied. In this work the influence of quercetin on satel-lite associated cucumber mosaic virus (CMV) infection and the response of Nicotiana megalosiphon host plants were investigated. Daily continuous flavonoid treatment of infected plants resulted in a significant increase in leaf mass and total protein synthesis. Attenuation of the yellowing symptom was also recorded, accompanied by lower expression of both viral and satellite replicative dsRna. This correlated with the decreased total peroxidase activity established in those plants. Expression of some glycoproteins (38 and 22.5 kDa), absent in healthy plants, were suppressed when infected plants were treated with quercetin. At the same time, some other infection-specific glycoproteins (22, 24 and 29 kDa) were significantly amplified by quercetin. The inability of quercetin to bind Cmv nucleoprotein or isolated ssRna was demonstrated. Quercetin has not shown any effect on Hsp70 synthesis in Cmv-infected plants.