Bai Xiaodong, Correa Valdir R, Toruño Tania Y, Ammar El-Desouky, Kamoun Sophien, Hogenhout Saskia A
Department of Entomology, The Ohio State University-OARDC, Wooster 44691, USA.
Mol Plant Microbe Interact. 2009 Jan;22(1):18-30. doi: 10.1094/MPMI-22-1-0018.
The fully sequenced genome of aster yellows phytoplasma strain witches' broom (AY-WB; Candidatus Phytoplasma asteris) was mined for the presence of genes encoding secreted proteins based on the presence of N-terminal signal peptides (SP). We identified 56 secreted AY-WB proteins (SAP). These SAP are candidate effector proteins potentially involved in interaction with plant and insect cell components. One of these SAP, SAP11, contains an N-terminal SP sequence and a eukaryotic bipartite nuclear localization signal (NLS). Transcripts for SAP11 were detected in AY-WB-infected plants. Yellow fluorescence protein (YFP)-tagged SAP11 accumulated in Nicotiana benthamiana cell nuclei, whereas the nuclear targeting of YFP-tagged SAP11 mutants with disrupted NLS was inhibited. The nuclear transport of YFP-SAP11 was also inhibited in N. benthamiana plants in which the expression of importin alpha was knocked down using virus-induced gene silencing (VIGS). Furthermore, SAP11 was detected by immunocytology in nuclei of young sink tissues of China aster plants infected with AY-WB. In summary, this work shows that AY-WB phytoplasma produces a protein that targets the nuclei of plant host cells; this protein is a potential phytoplasma effector that may alter plant cell physiology.
基于N端信号肽（SP）的存在，对翠菊黄化植原体女巫扫帚株系（AY-WB；暂定 asteris 植原体）的全序列基因组进行挖掘，以寻找编码分泌蛋白的基因。我们鉴定出56种AY-WB分泌蛋白（SAP）。这些SAP是潜在参与与植物和昆虫细胞成分相互作用的效应蛋白候选物。其中一种SAP，即SAP11，包含一个N端SP序列和一个真核双分型核定位信号（NLS）。在受AY-WB感染的植物中检测到了SAP11的转录本。黄色荧光蛋白（YFP）标记的SAP11在本氏烟草细胞核中积累，而NLS被破坏的YFP标记的SAP11突变体的核定位受到抑制。在利用病毒诱导基因沉默（VIGS）敲低输入蛋白α表达的本氏烟草植株中，YFP-SAP11的核转运也受到抑制。此外，通过免疫细胞学方法在受AY-WB感染的翠菊植株幼嫩库组织的细胞核中检测到了SAP11。总之，这项工作表明AY-WB植原体产生一种靶向植物宿主细胞核的蛋白；这种蛋白是一种潜在的植原体效应物，可能会改变植物细胞生理。
