The tomato (Solanum lycopersicum) callose synthase genes CalS11-like and CalS12-like encode proteins that are essential for the formation of callose, a major component of pollen mother cell walls; these enzymes also function in callose formation during pathogen infection. This article describes the targeting of these callose synthase mRNAs by a small RNA derived from the virulence modulating re...

Weed plants characteristic for potato and hop fields have not been considered in the past as potential hosts that could transmit and lead to spreading of potato spindle tuber (PSTVd) and hop stunt (HSVd) viroids, respectively. To gain insight into this problem, we biolistically inoculated these weed plants with viroid populations either as RNA or as cDNA. New potential viroid host species, coll...

Viroids are small autonomously replicating RNAs that share structural features with other subviral circular single-stranded RNAs of plants. Viroids and other circular single-stranded RNAs can be synthesised in vitro by a PCR-based procedure using a simple set of reactions. Two end-to-end primers are selected from a desired region of the viroid, one for the synthesis of the first strand cDNA and...

The peach latent mosaic viroid (PLMVd) is used to study the interactions between a viroid containing hammerhead ribozymes and its natural host, peach. To gain insight into the molecular basis of the phenotypic effects observed upon viroid infection, sequence variants from three PLMVd isolates that differ in symptom expression on the peach indicator GF-305 have been characterized. Analysis of th...

As a consequence of two unique physical properties, small size and circularity, viroid RNAs do not code for proteins and thus depend on RNA sequence/structural motifs for interacting with host proteins that mediate their invasion, replication, spread, and circumvention of defensive barriers. Viroid genomes fold up on themselves adopting collapsed secondary structures wherein stretches of nucleo...

Avocado sunblotch viroid, peach latent mosaic viroid, chrysanthemum chlorotic mottle viroid, and eggplant latent viroid (ELVd), the four recognized members of the family Avsunviroidae, replicate through the symmetric pathway of an RNA-to-RNA rolling-circle mechanism in chloroplasts of infected cells. Viroid oligomeric transcripts of both polarities contain embedded hammerhead ribozymes that, du...

For the identification of RNA-binding proteins that specifically interact with potato spindle tuber viroid (PSTVd), we subjected a tomato cDNA expression library prepared from viroid-infected leaves to an RNA ligand screening procedure. We repeatedly identified cDNA clones that expressed a protein of 602 amino acids. The protein contains a bromodomain and was termed viroid RNA-binding protein 1...

Plants can attenuate the replication of plant viruses and viroids by RNA silencing induced by virus and viroid infection. In higher plants, silencing signals such as small interfering RNAs (siRNAs) produced by RNA silencing can be transported systemically through phloem, so it is anticipated that antiviral siRNA signals produced in a stock would have the potential to attenuate propagation of vi...

The complete nucleotide sequence of apple scar skin viroid(ASSV) has been established, and a probable secondary structure is proposed. A single-stranded circular ASSV RNA consists of 330 nucleotides and can assume the rodlike conformation with extensive base-pairing characteristic of all the known viroids. ASSV shows low sequence homologies with other viroids and lacks the central conserved reg...

A major challenge in the agricultural industry is the development of techniques that can screen plant samples for viroid infection. Microarrays are promising in this regard, as their high throughput nature can potentially allow for the detection of a range of viroids in a single test. In this paper we present a microarray that can detect a wide spectrum of all 8 reported viroid genera including...