National Academy of Agricultural Sciences (NAAS)
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PRINT ISSN : 2319-7692
Online ISSN : 2319-7706 Issues : 12 per year Publisher : Excellent Publishers Email : editorijcmas@gmail.com / submit@ijcmas.com Editor-in-chief: Dr.M.Prakash Index Copernicus ICV 2018: 95.39 NAAS RATING 2020: 5.38 |
Viroids are plant sub viral pathogens with small, circular, single stranded and non-protein coding RNA genome that are currently known to infect only plants. These are the smallest self-replicating genetic units. These small RNAs contain all the information necessary to mediate replication, pathogenicity, intracellular and systemic trafficking. All or most of these functions likely result from direct interactions between distinct viroid RNA structural motifs and host cellular factors. The role of these motifs in overall biology of host viroid interactions have been studied in pospiviroidae and avsuniviroidae. Structural motif comprises nucleotides U43/C318 that form a small loop is required for trafficking from the bundle sheath into the phloem in Potato spindle tuber viroid (PSTVd). In Peach latent mosaic viroid (PLMVd) RNA with a specific structural motif of 12 to 13 nucleotides in left terminal folds into a hairpin, inhibits chloroplast development and results in complete albino phenotype by impairing transcription and translation of plastid rRNA and plastid encoded proteins respectively. Several experiments support that viroids trigger RNA silencing in their hosts. It is hypothesized that viroid-derived small RNAs (vd-siRNAs) targeting specific host DNA or mRNA sequences for transcriptional or posttranscriptional gene silencing respectively leads to viroid pathogenicity. Further research is needed to find out the role of all the structural motifs involved in establishment of infection, defense mechanism by plants against viroid, entry and exit in nucleus and chloroplast, participation of host proteins in specific steps replication, trafficking and molecular basis of viroid host range.
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