Noncoding RNAs of plant viruses and viroids: Sponges of host translation and RNA interference machinery


Publication Type:

Journal Article


Molecular Plant-Microbe Interactions, Volume 29, p.156-164 (2016)


<p>Noncoding sequences in plant viral genomes are well-known to control viral replication and gene expression in <em>cis</em>. However, plant viral and viroid noncoding (nc)RNA sequences can also regulate gene expression acting in <em>trans</em>, often acting like ‘sponges’ that bind and sequester host cellular machinery to favor viral infection. Noncoding sequences of small subgenomic (sg)RNAs of <em>Barley yellow dwarf virus</em> (BYDV) and <em>Red clover necrotic mosaic virus</em> (RCNMV) contain a cap-independent translation element that binds translation initiation factor eIF4G. We provide new evidence that a sgRNA of BYDV can globally attenuate host translation, probably by sponging eIF4G. Subgenomic ncRNA of RCNMV is generated via 5′ to 3′ degradation by a host exonuclease. The similar noncoding subgenomic flavivirus (sf)RNA, inhibits the innate immune response, enhancing viral pathogenesis. <em>Cauliflower mosaic virus</em> transcribes massive amounts of a 600-nt ncRNA, which is processed into small RNAs that overwhelm the host’s RNA interference (RNAi) system. Viroids use the host RNAi machinery to generate viroid-derived ncRNAs that inhibit expression of host defense genes by mimicking a microRNA. More examples of plant viral and viroid ncRNAs are likely to be discovered, revealing fascinating new weaponry in the host-virus arms race.</p>