Xiao Zeyi, Deng Jinmin, Liu Jiayao, Yuan Yuan, Tian Weiyin, Jiang Shengyu, Li Qiao, Yang Yang, Wu Gentu, Qing Ling, Li Mingjun
Chongqing Key Laboratory of Plant Disease Biology, College of Plant Protection, Southwest University, Chongqing, China.
Key Laboratory of Agricultural Biosafety and Green Production of Upper Yangtze River (Ministry of Education), Southwest University, Chongqing, China.
Pest Manag Sci. 2025 Sep;81(9):5146-5159. doi: 10.1002/ps.8869. Epub 2025 May 7.
Tobacco curly shoot virus (TbCSV, Begomovirus, Geminiviridae) is a viral agent that poses a serious threat to economically important crops like tomato and tobacco in Southwest China. The geminiviral V2 protein has been demonstrated to play multifunctional roles essential for viral infection and pathogenicity. This study comprehensively investigated the biological importance of five cysteines within the conserved 'WCCH' motif of the TbCSV V2 protein, and evaluated the effects of cysteine mutations on viral pathogenicity and the efficacy for cross-protection against wild-type severe TbCSV train.
Site-directed mutagenesis revealed that among the five cysteines in the V2 protein, C84, C86 and C89 residues are critical for its RNA silencing suppression activity, with C84 being the only residue whose mutation impaired its ability to induce tissue necrosis when expressed by potato virus X (PVX). Mutations at C84, C86 or C89 attenuated viral pathogenicity, and the mild symptoms were accompanied by reduced viral accumulations in Nicotiana benthamiana plants. Notably, pre-inoculation with the attenuated TbCSV mutant C84A in N. benthamiana and tomato plants conferred effective cross-protection against subsequent challenge infection by wild-type TbCSV.
The cysteine residues within the 'WCCH' motif of TbCSV V2 protein play distinct roles in its functions and viral pathogenicity. Importantly, the attenuated C84A mutant generated in this study not only offers insights into the pathogenic mechanisms of TbCSV but also holds promise for application in crop protection through cross-protection strategy in the field. © 2025 Society of Chemical Industry.
烟草曲茎病毒（TbCSV，双生病毒科，菜豆金色花叶病毒属）是一种病毒病原体，对中国西南部番茄和烟草等经济作物构成严重威胁。双生病毒的V2蛋白已被证明在病毒感染和致病性方面发挥着多种重要作用。本研究全面调查了TbCSV V2蛋白保守“WCCH”基序内五个半胱氨酸的生物学重要性，并评估了半胱氨酸突变对病毒致病性的影响以及对野生型重度TbCSV株系的交叉保护效果。
定点诱变显示，在V2蛋白的五个半胱氨酸中，C84、C86和C89残基对其RNA沉默抑制活性至关重要，其中C84是唯一突变后会损害其由马铃薯X病毒（PVX）表达时诱导组织坏死能力的残基。C84、C86或C89位点的突变减弱了病毒致病性，在本氏烟草植株中，轻微症状伴随着病毒积累量的减少。值得注意的是，在本氏烟草和番茄植株中预先接种减毒的TbCSV突变体C84A，可有效交叉保护植株免受随后野生型TbCSV的挑战感染。
TbCSV V2蛋白“WCCH”基序内的半胱氨酸残基在其功能和病毒致病性中发挥着不同作用。重要的是，本研究中产生的减毒C84A突变体不仅有助于深入了解TbCSV的致病机制，还有望通过田间交叉保护策略应用于作物保护。© 2025化学工业协会。
