Laboratory of Plant Virology, Department of Plant Pathology, College of Plant Protection, Shandong Agricultural University, Tai'an, Shandong 271018, China.
Shandong Provincial Key laboratory for Agricultural Microbiology, Tai'an, Shandong, 271018, China.
Sci Rep. 2017 Feb 23;7:43455. doi: 10.1038/srep43455.
Chloroplast-bound vesicles are key components in viral replication complexes (VRCs) of potyviruses. The potyviral VRCs are induced by the second 6 kDa protein (6K2) and contain at least viral RNA and nuclear inclusion protein b. To date, no chloroplast protein has been identified to interact with 6K2 and involve in potyvirus replication. In this paper, we showed that the Photosystem II oxygen evolution complex protein of Nicotiana benthamiana (NbPsbO1) was a chloroplast protein interacting with 6K2 of Tobacco vein banding mosaic virus (TVBMV; genus Potyvirus) and present in the VRCs. The first 6 kDa protein (6K1) was recruited to VRCs by 6K2 but had no interaction with NbPSbO1. Knockdown of NbPsbO1 gene expression in N. benthamiana plants through virus-induced gene silencing significantly decreased the accumulation levels of TVBMV and another potyvirus Potato virus Y, but not Potato virus X of genus Potexvirus. Amino acid substitutions in 6K2 that disrupted its interaction with NbPsbO1 also affected the replication of TVBMV. NbPsbP1 and NbPsbQ1, two other components of the Photosystem II oxygen evolution complex had no interaction with 6K2 and no effect on TVBMV replication. To conclude, 6K2 recruits 6K1 to VRCs and hijacks chloroplast protein NbPsbO1 to regulate potyvirus replication.
质体结合小泡是马铃薯 Y 病毒（属 Potyvirus）等正黏病毒复制复合物（VRC）的关键组成部分。VRC 由第二 6kDa 蛋白（6K2）诱导产生，至少包含病毒 RNA 和核内含蛋白 b。迄今为止，尚未发现与 6K2 相互作用并参与正黏病毒复制的质体蛋白。本文中，我们发现了烟草原生质体Ⅱ型光系统放氧复合体蛋白（NbPsbO1）与烟草叶脉镶嵌病毒（TVBMV；属 Potyvirus）的 6K2 相互作用，并存在于 VRC 中。第一 6kDa 蛋白（6K1）通过 6K2 被招募到 VRC 中，但与 NbPSbO1 没有相互作用。通过病毒诱导的基因沉默技术在烟草原生质体中敲低 NbPsbO1 基因的表达水平，可显著降低 TVBMV 和另一种正黏病毒马铃薯 Y 病毒的积累水平，但对属 Potexvirus 的马铃薯 X 病毒没有影响。6K2 中的氨基酸取代破坏了其与 NbPsbO1 的相互作用，也影响了 TVBMV 的复制。第二型光系统放氧复合体的另外两个组成部分 NbPsbP1 和 NbPsbQ1 与 6K2 没有相互作用，对 TVBMV 的复制也没有影响。总之，6K2 招募 6K1 到 VRC 中，并劫持质体蛋白 NbPsbO1 来调节正黏病毒的复制。
