Szittya G, Burgyán J
Agricultural Biotechnology Center, 2101 Gödöllo, Hungary.
J Virol. 2001 Mar;75(5):2411-20. doi: 10.1128/JVI.75.5.2411-2420.2001.
Avirulent genes either directly or indirectly produce elicitors that are recognized by specific receptors of plant resistance genes, leading to the induction of host defense responses such as hypersensitive reaction (HR). HR is characterized by the development of a necrotic lesion at the site of infection which results in confinement of the invader to this area. Artificial chimeras and mutants of cymbidium ringspot (CymRSV) and the pepper isolate of tomato bushy stunt (TBSV-P) tombusviruses were used to determine viral factors involved in the HR resistance phenotype of Datura stramonium upon infection with CymRSV. A series of constructs carrying deletions and frameshifts of the CymRSV coat protein (CP) undoubtedly clarified that an 860-nucleotide (nt)-long RNA sequence in the CymRSV CP coding region (between nt 2666 and 3526) is the elicitor of a very rapid HR-like response of D. stramonium which limits the virus spread. This finding provides the first evidence that an untranslatable RNA can trigger an HR-like resistance response in virus-infected plants. The effectiveness of the resistance response might indicate that other nonhost resistance could also be due to RNA-mediated HR. It is an appealing explanation that RNA-mediated HR has evolved as an alternative defense strategy against RNA viruses.
无毒基因直接或间接产生能被植物抗性基因的特定受体识别的激发子，从而引发宿主防御反应，如过敏反应（HR）。HR的特征是在感染部位形成坏死斑，这使得入侵者被限制在该区域。利用大花蕙兰环斑病毒（CymRSV）和番茄丛生矮缩病毒辣椒分离株（TBSV-P）的人工嵌合体和突变体，来确定感染CymRSV后曼陀罗中参与HR抗性表型的病毒因子。一系列携带CymRSV外壳蛋白（CP）缺失和移码的构建体无疑表明，CymRSV CP编码区中一段860个核苷酸（nt）长的RNA序列（在nt 2666和3526之间）是曼陀罗快速HR样反应的激发子，这种反应限制了病毒传播。这一发现首次证明了不可翻译的RNA能在病毒感染的植物中引发HR样抗性反应。抗性反应的有效性可能表明其他非寄主抗性也可能是由RNA介导的HR引起的。RNA介导的HR作为一种对抗RNA病毒的替代防御策略而进化，这是一个很有吸引力的解释。
