Although many subviral RNAs reduce or intensify disease symptoms caused by the helper virus, only recently have clues concerning the mechanism of disease modulation been revealed. New models for DI RNA-mediated reduction in helper virus levels and symptom attenuation include DI RNA enhancement of posttranscriptional gene silencing (PTGS), which is an antiviral defense mechanism in plants. Symptom enhancement by the satRNA of Cucumber mosaic virus is caused by minus-strand induction of the programmed cell death pathway. In contrast, symptom enhancement by satC of Turnip crinkle virus is due to satC interference with virion formation, leading to increased levels of free coat protein, which is the viral suppressor of PTGS. Mutualism between satRNA and helper virus can be seen for the satRNA of Groundnut rosette virus, which contributes to the virus by allowing virion assembly. These novel findings are leading to re-evaluation of the relationships between subviral RNAs, helper viruses, and hosts.

中文翻译：

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植物病毒卫星和有缺陷的干扰RNA：新世纪的新范例。

尽管许多亚病毒RNA减轻或加剧了由辅助病毒引起的疾病症状，但直到最近才发现有关疾病调节机制的线索。DI RNA介导的辅助病毒水平降低和症状减轻的新模型包括转录后基因沉默（PTGS）的DI RNA增强，这是植物中的一种抗病毒防御机制。黄瓜花叶病毒的satRNA引起的症状增强是由负链诱导的程序性细胞死亡途径引起的。相反，satC对芜菁皱纹病毒的症状增强是由于satC对病毒体形成的干扰，导致游离外壳蛋白水平升高，该蛋白是PTGS的病毒抑制剂。花生玫瑰花结病毒的satRNA可以看到satRNA与辅助病毒之间的相互关系，通过允许病毒粒子组装而有助于病毒。这些新颖的发现导致对亚病毒RNA，辅助病毒和宿主之间关系的重新评估。