DIFFERENTIAL INTERACTIONS OF BAMBOO MOSAIC POTEXVIRUS SATELLITE RNAS,HELPER VIRUS, AND HOST PLANTS

Bamboo mosaic potexvirus (BaMV) supports the replication and encapsida tion of a single-stranded satellite RNA (satBaMV), Full-length infecti ous cDNA clones of satBaMV variants with a 0.7 to 7.5% difference in n ucleotide sequence were constructed, and in vitro transcripts were co- inoculated with BaMV RNA to barley protoplasts. Coinoculation with BSL 6 satBaMV transcripts resulted in a greatly reduced accumulation of ge nomic and subgenomic RNAs whereas co-inoculation with the prototype BS F4 or other variants did not, satBaMV variant BSL6-mediated interferen ce occurred at the genomic RNA, subgenomic RNA, and capsid protein lev els whereas the synthesis of minus strand was not significantly affect ed. Attenuation of the BaMV symptoms also was observed in Chenopodium quinoa and Nicotiana benthamiana plants co-inoculated with BSL6 satBaM V, In protoplasts of barley and N, benthamiana, BSF4 and BSL6 variants replicated at a similar level whereas in the inoculated leaves of C. quinoa and N, benthamiana BSL6 accumulated to a much lower level than BSF4, and was encapsidated. BSL6 satBaMV was rarely detected in the sy stemic leaves of N, benthamiana co-inoculated with BaMV RNA, indicatin g that BSL6 satBaMV may be a movement-inefficient variant. It is sugge sted that this variant may provide a potential source for both resista nce against BaMV and insights into the interactions of satellite RNA, helper virus, and symptom expression.