Infectious mutants of cassava latent virus generatedin vivofrom intact recombinant DNA clones containing single copies of the genome

Abstract

Intact recombinant DNAs containing single copies of either component of the cassava latent virus genome can elicit infection when mechanically inoculated to host plants in the presence of the appropriate second component. Characterisation of infectious mutant progeny viruses, by analysis of virus-specific supercoiled DNA intermediates, indicates that most if not all of the cloning vector has been deleted, achieved at least in some cases by intermolecular recombination in vivo between DNAs 1 and 2. Significant rearrangements within the intergenic region of DNA 2, predominantly external to the common region, can be tolerated without loss of infectivity suggesting a somewhat passive role in virus multiplication for the sequences in question. Although packaging constraints might impose limits on the amount of DNA within geminate particles, isolation of an infectious coat protein mutant defective in virion production suggests that packaging is not essential for systemic spread of the viral DNA.

Regulation of African cassava mosaic virus complementary-sense gene expression by N-terminal sequences of the replication-associated protein AC1

“…The coat protein caused a significant (30-40 %) reduction in complementary-sense gene expression. Although it is known that the coat protein affects the relative levels of ssDNA and dsDNA (Stanley & Townsend, 1986;Sunter et al, 1990), its influence on gene expression has not been reported previously. While it is possible that the coat protein has a specific effect on complementary-sense expression, it could cause a general reduction in the level of gene expression simply as a result of its ability to bind to dsDNA (Ingham et al, 1995), in this instance to the GUS expression cassettes.…”

“…Virion-sense gene A V1 encodes the coat protein (Townsend et al, 1985). A function has yet to be assigned to the overlapping gene, A V2, and neither virion-sense gene is required for systemic infection of Nicotiana benthamiana (Stanley & Townsend, 1986;Etessami et al, 1989). Of the four overlapping complementary-sense genes, AC1 is essential for viral DNA replication (Brough et al, 1988;Elmer et al, 1988;Etessami et al, 1991), AC2 transactivates the expression of coat protein and DNA B genes (Haley et al, 1992; and AC3 is required for normal levels of viral DNA replication (Sunter et al, 1990;Etessami et al, 1991;Morris et al, 1991).…”

The Subcellular Location of the Gene 1 Product of Cauliflower Mosaic Virus Is Consistent with a Function Associated with Virus Spread

“…The alterations included an increased diameter of the intersymplastic channel sufficient to allow virus particles to pass through and, in many cases, virus particles were observed within the channel. The presence of virus particles free in the cytoplasm and en route between cells argues strongly that such particles mediate the spread of infection in these tissues, although it cannot be excluded that other forms of nucleoprotein, or nucleic acid, may also be involved, particularly as isolates of tobacco rattle virus (Lister, 1966) or cassava latent virus (Stanley & Townsend, 1986) that lack coat protein can infect plants systemically.…”

Complete nucleotide sequence of pepper huasteco virus: analysis and comparison with bipartite geminiviruses

“…Several experiments in which components of bipartite geminiviruses were exchanged (pseudorecombination) have been recently reported yon Arnim & Stanley, 1992). This pseudorecombination mechanism can now be added to the intermolecular recombination reported for ACMV (Etessami et al, 1989;Klinkenberg et at., 1989;Stanley & Townsend, 1986). Both mechanisms, independently or acting in a concerted manner, might be important in nature for the generation of new viruses.…”