We investigated virus infection rates in Japanese garlic plants and found that a potyvirus, onion yellow dwarf virus (OYDV) was always associated with another potyvirus, leek yellow stripe virus (LYSV). When the OYDV HC-Pro genes from those viral isolates were PCR-amplified and sequenced, we found that all the HC-Pros isolated from Japanese garlic lacked a long stretch of the N-terminal amino acids (~ 100 residues) including the KITC motif, suggesting possible loss of viral aphid transmission. Our phylogenetic analysis revealed that HC-Pros were divided into three major groups and that they did not branch from a single common ancestor, suggesting different mechanisms for generation of the short HC-Pros from the intact ones. Because HC-Pro is a well-known RNA silencing suppressor (RSS), we then analyzed the RSS activity of HC-Pro using the conventional agroinfiltration assay with Nicotiana benthamiana and also with onion, which is a natural host of OYDV. The results demonstrated that the short HC-Pro had reduced RSS activity compared to the long HC-Pro while both type HC-Pros were well expressed in the agroinfiltrated tissues. In addition, the tested OYDV HC-Pros exhibited more efficient RSS activity in onion than in N. benthamiana. We presume that OYDV with reduced RSS activity of HC-Pro may take advantage of mixed infection with LYSV to survive.

中文翻译：

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带有N末端缺失的洋葱黄矮病毒HC-Pro的RNA沉默抑制活性降低可能与大蒜中另一种波多病毒的混合感染相辅相成

我们对日本大蒜植物中的病毒感染率进行了调查，结果发现，马铃薯小病毒洋葱黄矮病毒（OYDV）始终与另一马铃薯小病毒韭菜黄条纹病毒（LYSV）相关。对来自这些病毒分离株的OYDV HC-Pro基因进行PCR扩增和测序后，我们发现，从大蒜中分离出的所有HC-Pro都缺少包括KITC序列在内的N端氨基酸（〜100个残基）的长链。 ，提示病毒蚜虫传播可能丧失。我们的系统发育分析表明，HC-Pro分为三大类，它们不是从一个共同的祖先分支的，这表明从完整的HC-Pro生成短HC-Pro的机制不同。由于HC-Pro是众所周知的RNA沉默抑制剂（RSS），烟草：本氏烟草以及洋葱，它是OYDV的天然宿主。结果表明，与长HC-Pro相比，短HC-Pro具有降低的RSS活性，而两种HC-Pro在农杆菌浸润组织中均能良好表达。另外，测试的OYDV HC-Pros在洋葱中比在本氏烟草中显示出更有效的RSS活性。我们假设HC-Pro的RSS活性降低的OYDV可能利用LYSV的混合感染生存。