In Vitro Synthesis of Cauliflower Mosaic Virus DNA in Viroplasms
Cauliflower Mosaic Virus (CaMV) is a DNA plant virus, and as such an attractive model for studying the molecular biology of plants (1, 2). Its genome is a circular double-stranded molecule, 8 kb in length. The encapsidated form possesses three single-stranded discontinuities (3) where the 5’ and 3’ ends of the interrupted strand overlap one another (4, 5). One interruption is on the transcribed strand a and the other two on the opposite strand 3. Viral DNA is also found in the nucleus as covalently closed supercoiled molecules associated with histones (6). The resulting minichromosomes are actively transcribed (7) into at least two polyadenylated transcripts: the 19S RNA, messenger for the viroplasm matrix protein, and the 35S RNA spanning the whole genome with a terminal redundancy of 180 nucleotides. A model for the replication of CaMV DNA which involves reverse transcription of the 35S RNA is emerging (refer to Pfeiffer et al, in this volume).
KeywordsViral Sequence Leaf Crude Extract Polyadenylated Transcript Terminal Redundancy Label Organelle
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