Observations concerning the discontinuous DNAs of cauliflower mosaic virus.

Abstract

The double-stranded circular DNA encapsidated within cauliflower mosaic virus (CaMV) particles contains three single-stranded discontinuities, two in one strand and one in the other, so that, upon denaturation, three linear singlestranded DNAs are produced. Here we show that a fourth much smaller single-stranded DNA, termed a1, is also present in denatured CaMV DNA preparations. The 5' extremity of a, is identical to that of the a-strand, the strand of DNA possessing only one interruption, while its 3' extremity lies just two nucleotides downstream from a major transcription initiation site. We also show that the interrupted strand at each discontinuity sometimes has a single ribonucleotide in place of a deoxyribonucleotide at its 5' extremity. Oligoribonucleotide chains of eight and 10 residues in length have also been detected at the 5' end of one of the discontinuities. These structures are thought to be the vestiges of primers which have not been completely excised prior to encapsidation of the DNA. The possibility that synthesis of the astrand occurs by reverse transcription of viral RNA using initiator tRNAmet as primer is discussed.

Rice tungro bacilliform virus DNA independently infects rice after Agrobacterium-mediated transfer

“…1). These features and their distribution are similar to those of CaMV, where the tRNA Met binds to the primary transcript and acts as the primer for the synthesis of the positive-sense DNA strand during replication (Hull & Covey, 1983;Guilley et al, 1983;Pfeiffer & Hohn, 1983). For agroinfection with CaMV, it is necessary to have a 'one-and-a-bitmer" clone, comprising an uninterrupted sequence giving rise to the full-length 35S transcript with terminal repeats (Grimsley & Bisaro, 1987).…”

A DNA polymerase activity is associated with Cauliflower Mosaic Virus

“…In the past year a model for CaMV replication has been put forward independently by several authors (11)(12)(13)(14)(15). It has been suggested that, as for the retroviruses (for review see ref.…”

Further Evidence that Viroplasms Are the Site of Cauliflower Mosaic Virus Genome Replication by Reverse Transcription during Viral Infection

“…Although this transcript is considered to be a possible polycistronic messenger (Dixon & Hohn, 1984), it could also represent an essential intermediate in the multiplication of the viral genome. Indeed, a replication model involving RNA-dependent synthesis of the CaMV DNA has been proposed (Guilley et al, 1983;Pfeiffer & Hohn, 1983;Hull & Covey, 1983). Such a model is now supported by numerous data obtained mainly from the characterization of intracellular CaMV DNA replication intermediates and from studies performed with isolated subcellular fractions active in viral DNA synthesis (for a review, s¢¢ Hull et al, 1987).…”