Comparison of Four Satellite RNA Isolates of Cucumber Mosaic Virus

Abstract

Four satellite RNA isolates of cucumber mosaic virus (CMV), S19-, T43-, T62- and T73-sat-RNAs were obtained from CMV-infected plants collected in Tochigi Prefecture of Japan. Their physical and biological properties were investigated. T43- and T62-satRNAs induced necrosis on tomato like Y-satRNA, whereas S19- and T73-satRNAs did not. T43-satRNA was found to be identical to T62-satRNA by nucleotide sequence determination. The sequences were compared with each other and with other satellite RNAs, revealing high degree of nucleotide sequence homology between S19-satRNA and Y-satRNA (91%) and between T43-satRNA and OY2-satRNA (94%). Further analyses of the three sequences indicate that no common open reading frame is present and thus, they do not seem to encode any protein products essential for their biological activity. Competition of the satellite RNAs with Y-satRNA was examined by mixed inoculations under the condition using tobacco as a host and CMV-O as a helper virus. The relative replication ability of T43-satRNA is superior to that of Y-satRNA while T73-satRNA is apparently similar to or a little better than Y-satRNA.