REPLICATION INTERMEDIATES OF RICE TUNGRO BACILLIFORM VIRUS-DNA SUPPORT A REPLICATION MECHANISM INVOLVING REVERSE TRANSCRIPTION

Rice tungro bacilliform virus (RTBV) replication intermediates have be en studied in rice plants infected with the virus. Unencapsidated viru s-specific molecules were identified which had open circular, linear, supercoiled (SC), strong-stop, single-stranded, linear double-stranded hairpin, and double-stranded with single-stranded extension DNA forms . The structures of these different DNA forms were consistent with the replication model of cauliflower mosaic virus and support other resul ts that reverse transcription is involved in the replication of RTBV. The existence of nonspecific and defective (+)-strand priming is sugge sted. The relative amount of SC DNAs differs in various tissues of the same plant and in the same tissue at different ages. This indicates h ost regulation of the virus replication cycle and a feedback regulator y mechanism in controlling the SC DNA level. There are no obvious diff erences in the composition of the replication intermediates between in sect-infected and agroinoculated rice plants. (C) 1994 Academic Press, Inc.