Citrus yellow mosaic badnavirus (CMBV) causes mosaic disease in all economically important citrus cultivars of India, with losses reaching up to 70%. CMBV belongs to the genus Badnavirus, family Caulimoviridae, possessing a circular double-stranded (ds) DNA genome with six open reading frames (ORFs I to VI), whose functions are yet to be deciphered. The RNA-silencing suppressor (RSS) activity has not been assigned to any CMBV ORF as yet. In the present study, it was found that ORFI exhibited RSS activity among all the six CMBV ORFs tested. Studies were done by employing the well-established Agrobacterium-mediated transient assay based on the transgenic Nicotiana benthamiana 16c plant line expressing the green fluorescent protein (GFP). The RSS activity of ORFI was confirmed by the analysis of the GFP visual expression in the agroinfiltrated leaves, further supported by quantification of GFP expression by RT-PCR. Based on the GFP visual expression, the CMBV ORFI was a weak RSS when compared to the p19 protein of tomato bushy stunt virus. In contrast, the ORFII, ORFIV, ORFV, ORFVI, and CP gene did not exhibit any RSS activity. Hence, ORFI is the first ORF of CMBV to be identified with RNA-silencing suppression activity.

柑橘黄色花叶病毒 (CMBV) 在印度所有具有重要经济意义的柑橘品种中引起花叶病，损失高达 70%。CMBV属于埃希Badnavirus，家庭花椰菜病毒科，具有六个开放阅读框（ORF I至VI），其职能是尚未被破译一个环状双链（DS）DNA基因组。RNA 沉默抑制 (RSS) 活性尚未分配给任何 CMBV ORF。在本研究中，发现 ORFI 在测试的所有六个 CMBV ORF 中都表现出 RSS 活性。研究是通过采用基于转基因本氏烟草的成熟农杆菌介导的瞬时测定法进行的表达绿色荧光蛋白 (GFP) 的 16c 植物系。ORFI 的 RSS 活性通过农杆菌渗入叶中 GFP 视觉表达的分析得到证实，通过 RT-PCR 对 GFP 表达的定量进一步支持。根据 GFP 视觉表达，与番茄浓密特技病毒的 p19 蛋白相比，CMBV ORFI 是弱 RSS。相比之下，ORFII、ORFIV、ORFV、ORFVI 和 CP 基因没有表现出任何 RSS 活性。因此，ORFI 是第一个被鉴定具有 RNA 沉默抑制活性的 CMBV 的 ORF。