A novel satellite RNA of cucumber mosaic virus induces unique line-pattern mosaic symptoms in tobacco

The CMV(YW) isolate of cucumber mosaic virus (CMV) induced unique line-pattern mosaic symptoms in systemically infected leaves of tobacco (Nicotiana tabacum cv. Ky57). By northern hybridization analysis using cDNA to CMV(Y) satellite RNA as a probe, it was confirmed that CMV(YW) contained a satellite RNA, which was designated sat-YW RNA; this was 388 nucleotides in length and did not have either a conserved domain that induces necrosis in tomato or chlorosis in tobacco. CMV(YW) free of sat-YW RNA, which was isolated by the single lesion isolation method using Chenopodium amaranticolor, did not induce the unique line-pattern mosaic symptom. Furthermore, the sat-YW RNA-mediated line-pattern mosaic symptom was also induced by in vitro transcribed infectious sat-YW RNA in tobaccos infected with either CMV(YW) or CMV(Y) genomic RNA. These results clearly demonstrated that sat-YW RNA induces the unique line-pattern mosaic symptom on CMV-infected tobaccos.