TRANS-ACTING UNTRANSLATED ELEMENTS OF GROUNDNUT ROSETTE VIRUS SATELLITE RNA ARE INVOLVED IN SYMPTOM PRODUCTION

Isolates of groundnut rosette umbravirus (GRV) contain a satellite RNA (sat-RNA), about 900 nucleotides (nt) in length, different variants o f which are responsible for the symptoms of different forms of rosette disease in groundnuts and, in the particular instance of sat-RNA YB3b , for the production of yellow blotch symptoms in Nicotiana benthamian a. Sat-RNA YB3b does not affect the accumulation of GRV genomic or sub genomic RNAs in infected plants. Replication of sat-RNA YB3b and induc tion of yellow blotch symptoms do not require the production of any sa t-RNA-encoded proteins. Experiments with deletion mutants identified t hree functional untranslated elements in sat-RNA YB3b. One (designated R) comprises nt 47-281, is essential for sat-RNA replication and appe ars to be cis-acting. The other two (designated A and B) comprise nt 2 80-470 and 629-849, respectively, are both involved in yellow blotch s ymptom production and can act in trans. Element A contains the determi nant that is unique to sat-RNA YB3b. The process of symptom induction by sat-RNA YB3b apparently involves a novel type of specific interacti on of two untranslated RNA elements, which can complement each other, with a host factor or factors.