HC-Pro as a tool to study silencing suppressor-mediated induction of disease symptoms in plants.

了解病毒感染后症状发展的机制，对设计抗病毒植物的新策略具有重要意义。一般来说，由痘病毒引起的症状是基于其中一种蛋白质的细胞效应，即辅助成分蛋白酶（HC-Pro）。在植物中，HC-Pro干扰小RNA的代谢和功能，这种干扰与植物的异常发育有关。HC-Pro的中心区域与抑制活性和RNA结合有关。西葫芦黄花叶病毒（ZYMV） HC-Pro的一个高度保守的氨基酸基序（FRNK）突变将严重的野生型毒株显著地改变为无症状毒株，但不影响其在南瓜植物中的积累，并且抑制活性保持不变。这种突变将症状从病毒积累中分离出来的能力为研究症状的病因创造了一个独特的机会。在其他多病毒科中，HC-Pro的这种突变总是导致传染性丧失。我们的目标是确定这个保守的ZYMV HC-Pro基序的突变和其他突变如何影响瓜类植物中宿主对痘病毒感染的反应。我们将特别关注HC-Pro对小RNA积累的影响。

It is important to understand the mechanisms of symptom development in response to virus infection to design new strategies to produce virus resistant plants. In general, symptoms induced by potyviruses are based on the cellular effects of one of their proteins, the helper-component proteinase (HC-Pro). In plants, the HC-Pro interferes with small RNA metabolism and function, and such interference is associated with anomalous plant development. The central region in the HC-Pro is associated with suppressor activity and RNA binding. A mutation within a highly conserved amino acid (FRNK) motif of the zucchini yellow mosaic virus (ZYMV) HC-Pro dramatically changes the severe wild type strain to an asymptomatic strain, but does not affect its accumulation in squash plants and suppressor activity is maintained. The ability of this mutation to uncouple symptoms from virus accumulation creates a unique opportunity to study the etiology of symptoms. In other potyviridae such a mutation in the HC-Pro always resulted in loss of infectivity. Our goal is to determine how this and other mutations in this conserved ZYMV HC-Pro motif affect host responses to potyvirus infection in cucurbit plants. In particular, we will focus on the effect of HC-Pro on small RNA accumulation.