Roger Hull

Transcription of cauliflower mosaic virus DNA. Detection of transcripts, properties, and location of the gene encoding the virus inclusion body protein

We have detected several cauliflower mosaic virus transcripts in infected turnip leaves by northern-blot hybridization. These RNAs ranged in size from 0.9 to about 8 kb. Two species, a heterogeneous 7-to 8-kb RNA and a 2.3-kb RNA, accumulated radioactivity when CaMV-infected leaves were labeled with [32P]orthophosphate 20 days postinoculation. An abundant 62,000 MW polypeptide was synthesized in a rabbit reticulocyte lysate programmed with RNA from infected plants, but this polypeptide was absent when RNA from noninfected plants was used to direct translation. The 62,000 MW polypeptide was also the major in vitro product specified by virus-specific poly(A)+RNA purified by hybridization with CaMV DNA immobilized on DBM paper. The in vitro-synthesised 62,000 MW polypeptide was shown to be very similar to the major protein component of virus inclusion bodies by peptide fingerprint analysis. The 2.3-kb transcript is the mRNA encoding the 62,000 MW inclusion body protein. Crossed-contact hybridization mapping of this messenger on cloned CaMV DNA revealed that it is transcribed from the contiguous EcoR1 fragments d and b. The 7- to 8-kb RNA hybridized to all EcoR1 fragments and is probably a full-length primary transcript of the alpha-DNA strand.

The application of spot hybridization to the detection of DNA and RNA viruses in plant tissues.

A solid-phase nucleic acid hybridization technique for the detection of DNA and RNA viruses in plant tissues is described. The method involves spotting crude samples onto nitrocellulose and using 12P-labelled DNA hybridization probes. The limit of sensitivity is 5-20 pg virus/spot or approximately 5 micrograms/g leaf tissue. The method is quantitative for DNA viruses in crude homogenates, but not for RNA viruses. The amount of cauliflower mosaic virus in infected leaves and protoplasts was estimated. The amplitude of spot hybridization to screening plant material from glasshouses and field is discussed.

Alfalfa Mosaic Virus

Publisher Summary In 1931, Weimer reported that the causal agent of a mosaic disease of alfalfa was a virus, which he named alfalfa mosaic virus (AMV). This virus has subsequently received several other designations, including Alfalfa Virus I, Medicago Virus 2, Marmor rnedicaginis, and Lucerne Mosaic Virus, and R/1 1.3/18 U/U s/Ap. Various research workers have shown that this virus causes diseases in other crops, e.g., Potato Calico, noted by Hungerford. AMV was partially purified by Ross; thus it was the first aphid-transmitted virus to be purified. However, there was little interest in purified AMV until around 1960, when Bancroft and Kaesberg, Kelley and Kaesberg, and Gibbs et al., showed that virus preparations contain several components and that the virus particles, unlike those of other plant viruses, have a bacilliform shape, Subsequently, work on this virus has intensified with the studies on the structure and function of the components. This chapter is intended to bring together information on a wide range of topics and to offer some possible explanations of the unusual in vivo and in vitro behavior of this virus.

Cloning and sequence analysis of banana streak virus DNA.

Banana streak virus (BSV), a member of the Badnavirus group of plant viruses, causes severe problems in banana cultivation, reducing fruit yield and restricting plant breeding and the movement of germplasm. Current detection methods are relatively insensitive. In order to develop a PCR-based diagnostic method that is both reliable and sensitive, the genome of a Nigerian isolate of BSV has been sequenced and shown to comprise 7389 bp and to be organized in a manner characteristic of badnaviruses. Comparison of this sequence with those of other badnaviruses showed that BSV is a distinct virus. PCR with primers based on sequence data indicated that BSV sequences are present in the banana genome.

Replication of cauliflower mosaic virus and transcription of its genome in turnip leaf protoplasts

Abstract The replication of cauliflower mosaic virus (CaMV) was studied in turnip leaf protoplasts infected in culture with virus and in protoplasts isolated from infected plants. Production of mature virus in protoplasts infected in culture was synchronous but slow, requiring more than 4 days following infection. Virus assembly time in asynchronously infected cells (protoplasts from infected plants) was much shorter (10–15 hr), the difference considered to be the time in synchronous infection needed for the completion of replication cycle events prerequisite to virus assembly. About 2.5 days following synchronous infection in culture, a stable RNA species (apparent molecular weight of 1.5-1.8 × 10 6 ) coded by the CaMV genome appeared in infected protoplasts. The RNA species represented the coding capacity of a considerable portion (50–80%) of the CaMV genome as demonstrated by RNA-driven RNA-DNA hybridization reactions and by the hybridization of the viral RNA to Eco RI restriction fragments of the CaMV genome. The viral-coded RNA was the apparent product of asymmetrical transcription of the CaMV genome since it hybridized to only one DNA strand, the strand with one discontinuity. Other properties of the large viral-coded RNA suggest that it may serve a messenger function.

Does cauliflower mosaic virus replicate by reverse transcription

Abstract Cauliflower mosaic virus (CaMV) has an encapsidated genome of double-stranded DNA which exhibits several unusual features. These and other observations have led us to propose a model for CaMV replication which includes a reverse transcription step.

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

In nature, rice tungro disease is caused by an RNA and a DNA virus complex, but we have obtained an independently infectious clone of rice tungro bacilliform virus (RTBV) DNA. Infectivity could be demonstrated only when a more than unit-length copy was cloned in the Agrobacterium binary vector Bin 19 and agroinoculated into rice plants. Rice plants thus agroinfected with cloned RTBV DNA showed typical symptoms of tungro disease, presence of viral DNA and bacilliform particles, and could be used as a source of virus to infect healthy plants by the green leafhopper (Nephotettix virescens). The importance of this infectious clone in understanding the molecular biology of RTBV and the rice tungro disease is discussed.

Studies on alfalfa mosaic virus: I. The protein and nucleic acid

Abstract The molecular weight of the alfalfa mosaic virus (AMV) protein subunit was determined from amino acid analyses and specific staining for certain amino acids on peptide maps from tryptic and chymotryptic digests of the protein. A subunit molecular weight of 32,600 was confirmed by estimations of C-terminal and N-terminal residues and of the tryptophan content. AMV nucleic acid consisted of four components with sedimentation values of 24.3, 20.0, 17.3, and 12.7 S. The molecular weights of these components were estimated.

Approaches to nonconventional control of plant virus diseases

Abstract Plant viruses cause significant losses to crops worldwide and the three basic approaches to controlling them have not been overly successful. The new concept of nonconventional resistance, which involves transforming plants with nucleic acid sequences that interfere with the viral infection cycle, is a promising new approach. The current nonconventional strategies, those of coat protein‐mediated protection, antisense nucleic acids, satellite sequences, defective interfering molecules, and nonstructural genes, are reviewed with their advantages and disadvantages being discussed. The question of what exactly is nonconventional resistance is raised and suggestions are made for defining resistance. A range of strategies that are likely to be developed in the future are outlined together with some guiding principles for selection and deployment of these forms of resistance.

Retroid virus genome replication.

Publisher Summary Sixteen years have passed since reverse transcription was demonstrated in the replication cycle of retroviruses. This unique observation rationalized many earlier studies demonstrating that inhibitors of DNA synthesis prevented the establishment of infection by these RNA viruses. More recently, it has become apparent that reverse transcription is also used in the replication of two groups of DNA viruses. In 1982, evidence was obtained for a role of reverse transcription in the replication of hepadnaviruses, small DNA viruses of humans and animals, and it soon became clear that reverse transcription might also be involved in the replication of the caulimoviruses, a group of DNA viruses of plants. In 1983,it was pointed out that there were, in fact, striking similarities in the mechanisms by which retroviruses, hepadnaviruses, and caulimoviruses apparently used reverse transcription to replicate their genomes, and the supergroup name of retroid viruses was proposed.