College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou 310018, China.
Viruses. 2023 Jan 4;15(1):157. doi: 10.3390/v15010157.
The necrogenic strain N5 of tomato mosaic virus (ToMV-N5) causes systemic necrosis in tomato cultivar Hezuo903. In this work, we mapped the viral determinant responsible for the induction of systemic necrosis. By exchanging viral genes between N5 and a non-necrogenic strain S1, we found that movement protein (MP) was the determinant for the differential symptoms caused by both strains. Compared with S1 MP, N5 MP had an additional ability to increase virus accumulation, which was not due to its functions in viral cell-to-cell movement. Actually, N5 MP, but not S1 MP, was a weak RNA silencing suppressor, which assisted viral accumulation. Sequence alignment showed that both MPs differed by only three amino acid residues. Experiments with viruses having mutated MPs indicated that the residue isoleucine at position 170 in MP was the key site for MP to increase virus accumulation, but also was required for MP to induce systemic necrosis in virus-infected tomato plants. Collectively, the lethal necrosis caused by N5 is dependent on its MP protein that enhances virus accumulation via its RNA silencing suppressor activity, probably leading to systemic necrosis responses in tomato plants.
番茄花叶病毒致病变种 N5（ToMV-N5）可引起番茄品种“和硕 903”的系统性坏死。本研究对致系统性坏死的病毒决定因子进行了定位。通过在 N5 和非致病变种 S1 间交换病毒基因，发现运动蛋白（MP）是导致两株系产生差异症状的决定因子。与 S1 MP 相比，N5 MP 具有额外的增加病毒积累的能力，这与其在病毒细胞间运动中的功能无关。实际上，N5 MP 而非 S1 MP 是一个弱的 RNA 沉默抑制子，辅助了病毒积累。序列比对表明，两 MPs 仅相差 3 个氨基酸残基。具有突变 MP 的病毒实验表明，MP 第 170 位的异亮氨酸残基是 MP 增加病毒积累的关键位点，但也是 MP 诱导病毒感染番茄植株系统性坏死所必需的。总之，N5 引起的致死性坏死依赖于其 MP 蛋白，该蛋白通过 RNA 沉默抑制子活性增强病毒积累，可能导致番茄植株产生系统性坏死反应。
