Viruses, Viroids, and Prions

Genetic Modification of Plant Hormones Induced by Parasitic Nematodes, Virus, Viroid, Bacteria, and Phytoplasma in Plant Growing

“…Although viroids cause symptoms similar to viral infections in plants, they have exceptional structural, functional, and evolutionary features. Viroids are RNA with a minute genome varying between 250 and 401 bases, single-stranded, circular, non-protein-coding, and autonomously replicating RNA [75,76]. They need a host cell to reproduce.…”

An Inside Look into Biological Miniatures: Molecular Mechanisms of Viroids

“…Thereupon, in the next step, these (−) sense concatemers serve as templates for the synthesis of multimeric, linear (+) strand concatemers which subsequently are cleaved into monomeric (+) circles. In the alternate second pathway called symmetric, typical of Avsunviroidae ( Figure 2 ) [ 69 ], replication operates through two rolling circles wherein the multimeric linear (−) strands generated from the (+) sense RNA genome of the viroid undergo cleavage and ligation to generate circular (−) strand RNA monomers. These (−) strand circles then act as templates for the subsequent generation of linear, multimeric (+) strands which then cleave into (+) sense monomer genomes.…”

“…However, several research studies reported the accumulation of 21–24 nucleotide-long viroid-derived small RNAs [vd-sRNAs] in viroid-infected plants. Generation of vd-sRNAs impacts disease symptom expression in host plants ( Figure 3 [ 69 ]). This induction of vd-sRNAs was observed irrespective of the site of viroid replication and showed that viroids can induce RNA silencing of host genes [ 149 , 150 , 151 ].…”

“… Viroids induce disease by generating viroid small RNA (vsRNA) that elicit RNA interference. (Adapted from Clark et al, 2019 [ 69 ]). …”

Recent development in antiviral surfaces: Impact of topography and environmental conditions

“…There is a protective protein shell, capsid, inside the envelope that contains the genome of the virus which can either be DNA or RNA. Three different types of capsid shapes can be found in general; spherical, filamentous, and complex [ 6 ]. Capsid shape helps virus identification and additional information on virus-specific life cycles [ 7 ].…”