The rise of post-traumatic stress disorders.
Authors: G Jackson
Journal: BMJ (1991)

<h3>Abstract</h3> Satellites associated with plant or animal viruses have been largely detected and characterized, while those from mycoviruses together with their roles remain far less determined. Three dsRNA segments (dsRNA 1 to 3 termed according to their decreasing sizes) were identified in a strain of phytopathogenic fungus <i>Pestalotiopsis fici</i> AH1-1 isolated from a tea leaf. The complete sequences of dsRNAs 1 to 3, with the sizes of 10316, 5511, and 631 bp, were determined by random cloning together with a RACE protocol. Sequence analyses support that dsRNA1 is a genome of a novel hypovirus belonging to a newly proposed genus “Alphahypovirus” of the family <i>Hypoviridae</i>, tentatively named Pestalotiopsis fici hypovirus 1 (PfHV1); dsRNA2 is a defective RNA (D-RNA) generating from dsRNA1 with septal deletions; and dsRNA3 is the satellite component of PfHV1 since it could be co-precipitated with other dsRNA components in the same sucrose fraction by ultra-centrifuge, suggesting that it is encapsulated together with PfHV1 genomic dsRNAs. Moreover, dsRNA3 shares an identical stretch (170 bp) with dsRNAs 1 and 2 at their 5′ termini and the remaining is heterogenous, which is distinct from a typical satellite that generally has very little or no sequence similarity with helper viruses. More importantly, dsRNA3 lacks a substantial open reading frame (ORF) and a poly (A) tail, which is unlike the known satellite dsRNAs of hypoviruses, as well as unlike those in association with <i>Totiviridae</i> and <i>Partitiviridae</i> since the latters are encapsidated in coat proteins. As up-regulated expression of dsRNA3, dsRNA1 was significantly down-regulated, suggesting that dsRNA3 negatively regulates the expression of dsRNA1, whereas dsRNAs 1 to 3 have no obvious impact on the biological traits of the host fungus including morphologies and virulence. This study indicates that PfHV1 dsRNA3 is a special type of satellite-like nucleic acid that has substantial sequence homology with the host viral genome without encapsidation in a coat protein, which broadens the definition of satellite. <h3>IMPORTANCE</h3> Satellites in association with plant or animal viruses have been largely detected and characterized, while those from mycoviruses together with their roles remain far less determined. Here, a special satellite-like dsRNA (SatL-dsRNA) together with its helper virus, a novel hypovirus from <i>Pestalotiopsis fici</i>, was identified and characterized. This SatL-dsRNA lacks a substantial open reading frame and a poly (A) tail, which is unlike the known satellite dsRNAs of hypoviruses. It is also unlike those in association with <i>Totiviridae</i> and <i>Partitiviridae</i> since the latters are encapsidated in coat proteins. As up-regulated expression of the SatL-dsRNA, the helper virus genome was significantly down-regulated, suggesting that it negatively regulates the genomic expression of the helper virus. This special SatL-dsRNA has substantial sequence homology with the host viral genome and is not encapsidated in the coat protein of its helper virus, which represents a novel class of satellite-like nucleic acids, and it broadens the definition of satellite.