ANALYSIS OF THE DETERMINANTS OF THE SATELLITE RNA OF CUCUMBER MOSAIC CUCUMOVIRUS FOR HIGH ACCUMULATION IN SQUASH

Ix-satRNA is a 334-nt cucumber mosaic cucomovirus satellite RNA (CMV-s atRNA) with the unusual property of accumulating to high levels in hos t plants of the family Cucurbitaceae. To identify the determinants for this unusual phenotype, recombinant satRNAs were obtained, by in vitr o manipulation of full-length cDNA clones between clone-derived Ix5-sa tRNA and two other CMV-satRNAs that do not accumulate efficiently in s quash: D4-satRNA, which differs in 7 positions from Ix5-satRNA, and B2 1-satRNA, which differs in 45 positions. The analysis of the accumulat ion in squash of these hybrid satRNAs showed that determinants for hig h accumulation in squash occur in three molecular domains: nucleotides 1-46 (a C at position 20), 47-185 (a C at position 102), and 185-334 (not identified). None of these determinants seemed to be necessary or sufficient to confer a phenotype of high accumulation in squash. They resulted, or did not result, in such a phenotype according to the seq uences that occur in other parts of the satRNA molecule. Not all of th e identified determinants were equally affected by sequence context. T hese results may suggest that the phenotype in squash is determined by the conformation of the satRNA. (C) 1994 Academic Press, Inc.