School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia.
Plant Industry Division, CSIRO, P.O. Box 1600, Canberra, ACT 2601, Australia.
Viruses. 2017 Oct 10;9(10):294. doi: 10.3390/v9100294.
The plant viral family is divided into three genera: , and . Without assistance from another virus, members of the family are confined to the cells of the host plant's vascular system. The first open reading frame (ORF) of poleroviruses and enamoviruses encodes P0 proteins which act as silencing suppressor proteins (VSRs) against the plant's viral defense-mediating RNA silencing machinery. Luteoviruses, such as barley yellow dwarf virus-PAV (BYDV-PAV), however, have no P0 to carry out the VSR role, so we investigated whether other proteins or RNAs encoded by BYDV-PAV confer protection against the plant's silencing machinery. Deep-sequencing of small RNAs from plants infected with BYDV-PAV revealed that the virus is subjected to RNA silencing in the phloem tissues and there was no evidence of protection afforded by a possible decoy effect of the highly abundant subgenomic RNA3. However, analysis of VSR activity among the BYDV-PAV ORFs revealed systemic silencing suppression by the P4 movement protein, and a similar, but weaker, activity by P6. The closely related BYDV-PAS P4, but not the polerovirus potato leafroll virus P4, also displayed systemic VSR activity. Both luteovirus and the polerovirus P4 proteins also showed transient, weak local silencing suppression. This suggests that systemic silencing suppression is the principal mechanism by which the luteoviruses BYDV-PAV and BYDV-PAS minimize the effects of the plant's anti-viral defense.
， 和 。没有其他病毒的帮助，该科的成员局限于宿主植物维管束系统的细胞中。弹状病毒和披膜病毒的第一个开放阅读框（ORF）编码 P0 蛋白，作为沉默抑制蛋白（VSR），针对植物的病毒防御介导的 RNA 沉默机制。然而，黄矮病毒属病毒，如大麦黄花叶病毒-PAV（BYDV-PAV），没有 P0 来执行 VSR 作用，因此我们研究了 BYDV-PAV 编码的其他蛋白或 RNA 是否赋予对植物沉默机制的保护。用 BYDV-PAV 感染的植物的小 RNA 深度测序表明，病毒在韧皮部组织中受到 RNA 沉默的影响，并且没有可能由大量亚基因组 RNA3 产生的诱饵效应提供的保护证据。然而，对 BYDV-PAV ORF 中的 VSR 活性分析表明，P4 运动蛋白具有系统的沉默抑制作用，而 P6 则具有类似但较弱的作用。密切相关的 BYDV-PAS P4，但不是弹状病毒马铃薯卷叶病毒 P4，也表现出系统的 VSR 活性。两种黄矮病毒和杆状病毒 P4 蛋白也表现出短暂的、弱的局部沉默抑制。这表明系统的沉默抑制是黄矮病毒 BYDV-PAV 和 BYDV-PAS 最小化植物抗病毒防御效果的主要机制。
