RNA silencing is an evolutionarily conserved defense response against virus invasion and suppression of silencing is a counter-defense mechanism acquired by viruses. The B2 protein encoded by insect Flock House virus (FHVB2) is a well-known RNA silencing suppressor (RSS). It is capable of reversing the suppression of GFP reporter gene in planta. In this study the effect of point mutation and deletions of FHVB2 on the in planta RSS activity was quantified and validated. The results showed drastic reduction in RSS activity of point mutant and deletion constructs. It is known that viruses like Cucumber mosaic virus can enhance the ability of plants to tolerate abiotic stress although the underlying mechanism is not known. Since the non-plant virus encoded FHVB2 is functionally similar to Cucumber mosaic virus encoded 2b and can act as a RSS in plants, it was used to understand if there is any role of host RNA silencing activity in imparting stress tolerance. FHVB2 was overexpressed in tobacco and transgenics analyzed for response to different abiotic stress conditions. The transgenic plants could tolerate high concentrations of salt and showed enhanced accumulation of proline. Transient assays using point mutant and deletion constructs indicate that functional RSS activity is not required for salt tolerance.

中文翻译：

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由 Flock House 病毒编码的 RNA 沉默抑制因子 B2 蛋白在烟草植物中的过度表达导致对盐胁迫的耐受性

RNA 沉默是一种进化上保守的针对病毒入侵的防御反应，抑制沉默是病毒获得的反防御机制。由昆虫群居病毒 (FHVB2) 编码的 B2 蛋白是众所周知的 RNA 沉默抑制因子 (RSS)。它能够逆转植物中 GFP 报告基因的抑制。在这项研究中，量化并验证了 FHVB2 点突变和缺失对植物内 RSS 活性的影响。结果显示点突变体和缺失构建体的RSS活性急剧降低。众所周知，黄瓜花叶病毒等病毒可以增强植物对非生物胁迫的耐受能力，但其潜在机制尚不清楚。由于非植物病毒编码的 FHVB2 在功能上与编码 2b 的黄瓜花叶病毒相似，并且可以作为植物中的 RSS，它被用来了解宿主 RNA 沉默活性在赋予胁迫耐受性方面是否有任何作用。FHVB2 在烟草中过表达，分析转基因对不同非生物胁迫条件的反应。转基因植物可以耐受高浓度的盐分，并表现出增强的脯氨酸积累。使用点突变体和缺失构建体的瞬时测定表明，耐盐性不需要功能性 RSS 活性。