Yaegashi Hajime, Tamura Akihiro, Isogai Masamichi, Yoshikawa Nobuyuki
The United Graduate School of Agricultural Sciences, Iwate University, Morioka 020-8550, Japan.
Virology. 2008 Dec 20;382(2):199-206. doi: 10.1016/j.virol.2008.09.024. Epub 2008 Oct 26.
Apple chlorotic leaf spot virus 50 kDa movement protein (P50) acts as a suppressor of systemic silencing in Nicotiana benthamiana. Here, we investigate the mode of action of P50 suppressor. An agroinfiltration assay in GFP-expressing N. benthamiana line16c (GFP-plant) showed that P50 could not prevent the short-distance spread of silencing. In grafting experiments, the systemic silencing was inhibited in GFP-plants (scion) grafted on P50-expressing N. benthamiana (P50-plant; rootstock) when GFP silencing was induced in rootstock. In double-grafted plants, GFP-plant (scion)/P50-plant (interstock)/GFP-plant (rootstock), the systemic silencing in scion was inhibited when GFP silencing was induced in rootstock. Analysis of P50 deletion mutants indicated that the N-terminal region (amino acids 1-284) is important for its suppressor activity. In gel mobility shift assay, P50 lacks binding ability with siRNAs. These results indicated that P50 has a unique suppressor activity that specifically inhibits the long-distance movement of silencing signals.
苹果褪绿叶斑病毒50 kDa运动蛋白（P50）在本氏烟草中作为系统性沉默的抑制因子发挥作用。在此，我们研究了P50抑制因子的作用模式。在表达绿色荧光蛋白的本氏烟草品系16c（GFP植株）中进行的农杆菌浸润试验表明，P50不能阻止沉默的短距离传播。在嫁接实验中，当在砧木中诱导GFP沉默时，嫁接到表达P50的本氏烟草（P50植株；砧木）上的GFP植株（接穗）中的系统性沉默受到抑制。在双嫁接植株中，即GFP植株（接穗）/P50植株（中间砧）/GFP植株（砧木），当在砧木中诱导GFP沉默时，接穗中的系统性沉默受到抑制。对P50缺失突变体的分析表明，N端区域（氨基酸1 - 284）对其抑制活性很重要。在凝胶迁移率变动分析中，P50缺乏与小干扰RNA的结合能力。这些结果表明，P50具有独特的抑制活性，能特异性抑制沉默信号的长距离移动。
