Dimerization of the bacterial effector protein AvrBs3 in the plant cell cytoplasm prior to nuclear import
Dimerization of the bacterial effector protein AvrBs3 in the plant cell cytoplasm prior to nuclear import
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DOI：
10.1111/j.1365-313x.2005.02370.x
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发表时间：
2005-04-01
期刊：
影响因子：
7.2
通讯作者：
Bonas, U
中科院分区：
文献类型：
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作者：
Gürlebeck, D;Szurek, B;Bonas, U
来自细菌性植物病原体野油菜黄单胞菌致病变种的效应蛋白AvrBs 3。vesicatoria被转移到植物细胞中，在那里它特异性地诱导肥大症状或过敏反应。AvrBs 3的活性依赖于核定位信号（NLS）和酸性激活结构域，表明其在植物转录调控中的作用。在这里，我们表明，AvrBs 3二聚体在植物细胞之前，其核进口。在酵母双杂交系统中测试了AvrBs 3缺失衍生物，揭示了在抗性植物中赋予特异性识别并且对毒力功能至关重要的重复区域对于自我相互作用也是必不可少的。GST pull-down分析表明AvrBs 3-AvrBs 3相互作用的发生不依赖于植物蛋白。两种不同的失活突变体AvrBs 3衍生物在Bs 3抗性辣椒植物中的共表达导致“反式互补”，即，过敏反应的诱发这清楚地表明AvrBs 3-二聚化发生在植物中。有趣的是，在易感植物中没有观察到“反式互补”，这表明植物中AvrBs 3毒力功能需要野生型同二聚体。此外，一个绿色荧光蛋白（GFP）融合的AvrBs 3删除的NLS（AvrBs 3 Δ NLS-GFP），通常定位在细胞质中，导入细胞核后，与野生型AvrBs 3在本塞姆氏烟草共表达。因此，AvrBs 3二聚化在核输入之前发生在植物细胞的细胞质中。考虑到二聚化是转录调控因子的一个共同特征，我们的数据与AvrBs 3操纵植物基因表达的想法是一致的，该植物基因参与建立相容和不相容的相互作用。
The effector protein AvrBs3 from the bacterial phytopathogen Xanthomonas campestris pv. vesicatoria is translocated into the plant cell where it specifically induces hypertrophy symptoms or the hypersensitive reaction. Activity of AvrBs3 depends on nuclear localization signals (NLSs) and an acidic activation domain, suggesting a role in regulation of plant transcription. Here, we show that AvrBs3 dimerizes in the plant cell prior to its nuclear import. AvrBs3 deletion derivatives were tested in the yeast two-hybrid system revealing that the repeat region, which confers specific recognition in resistant plants and is crucial for virulence function, is also essential for the self-interaction. GST pull-down assays showed that the AvrBs3-AvrBs3 interaction occurs independent of plant proteins. Coexpression of two different inactive mutant AvrBs3 derivatives in Bs3-resistant pepper plants resulted in 'trans-complementation', i.e., the induction of a hypersensitive reaction. This clearly indicates that AvrBs3-dimerization occurs in planta. Interestingly, 'trans-complementation' was not observed in susceptible plants suggesting that wild-type homodimers are needed for the AvrBs3 virulence function in plants. Furthermore, a green fluorescent protein (GFP) fusion of AvrBs3 deleted in the NLSs (AvrBs3 Delta NLS-GFP), normally localized in the cytoplasm, was imported into the nucleus upon coexpression with wild-type AvrBs3 in Nicotiana benthamiana. Thus, AvrBs3 dimerization takes place in the cytoplasm of the plant cell prior to nuclear import. Given the fact that dimerization is a common feature of transcriptional regulators, our data are consistent with the idea that AvrBs3 manipulates expression of plant genes involved in the establishment of compatible and incompatible interactions.