Department of Plant Pathology, University of California, Davis, CA, 95616, USA.
Department of Plant Protection, School of Agriculture, The University of Jordan, Amman, 11942, Jordan.
New Phytol. 2021 Jul;231(1):382-398. doi: 10.1111/nph.17370. Epub 2021 Apr 21.
Plant virus movement proteins (MPs) facilitate virus spread in their plant hosts, and some of them are known to target plasmodesmata (PD). However, how the MPs target PD is still largely unknown. Carrot mottle virus (CMoV) encodes the ORF3 and ORF4 proteins, which are involved in CMoV movement. In this study, we used CMoV as a model to study the PD targeting of a plant virus MP. We showed that the CMoV ORF4 protein, but not the ORF3 protein, modified PD and led to the virus movement. We found that the CMoV ORF4 protein interacts with the host cell small ubiquitin-like modifier (SUMO) 1, 2 and the SUMO-conjugating enzyme SCE1, resulting in the ORF4 protein SUMOylation. Downregulation of mRNAs for NbSCE1 and NbSUMO impaired CMoV infection. The SUMO-interacting motifs (SIMs) LVIVF, VIWV, and a lysine residue at position 78 (K78) are required for the ORF4 protein SUMOylation. The mutation of these motifs prevented the protein to efficiently target PD, and further slowed or completely abolished CMoV systemic movement. Finally, we found that some of these motifs are highly conserved among umbraviruses. Our data suggest that the CMoV ORF4 protein targets PD by interacting with the host cell SUMOylation system.
植物病毒运动蛋白（MPs）促进病毒在其植物宿主中的传播，其中一些已知靶向胞间连丝（PD）。然而，MP 如何靶向 PD 在很大程度上仍然未知。胡萝卜斑驳病毒（CMoV）编码 ORF3 和 ORF4 蛋白，它们参与 CMoV 的运动。在这项研究中，我们使用 CMoV 作为模型来研究植物病毒 MP 对 PD 的靶向。我们表明，CMoV 的 ORF4 蛋白而不是 ORF3 蛋白修饰了 PD 并导致病毒运动。我们发现 CMoV ORF4 蛋白与宿主细胞小泛素样修饰物（SUMO）1、2 和 SUMO 连接酶 SCE1 相互作用，导致 ORF4 蛋白 SUMO 化。NbSCE1 和 NbSUMO 的 mRNA 下调会损害 CMoV 感染。SUMO 相互作用基序（SIM）LVIVF、VIWV 和位置 78 处的赖氨酸残基（K78）是 ORF4 蛋白 SUMO 化所必需的。这些基序的突变阻止了该蛋白有效地靶向 PD，并进一步减缓或完全阻止了 CMoV 的系统运动。最后，我们发现这些基序中的一些在 Umbraviruses 中高度保守。我们的数据表明，CMoV ORF4 蛋白通过与宿主细胞 SUMO 化系统相互作用来靶向 PD。
