Symbiosis-promoting and deleterious effects of NopT, a novel type 3 effector of Rhizobium sp strain NGR234
Symbiosis-promoting and deleterious effects of NopT, a novel type 3 effector of Rhizobium sp strain NGR234
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DOI：
10.1128/jb.00306-08
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发表时间：
2008-07-01
影响因子：
3.2
通讯作者：
Staehelin, Christian
中科院分区：
文献类型：
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作者：
Dai, Wei-Jun;Zeng, Yong;Staehelin, Christian
某些寄主植物和固氮菌(根瘤菌)之间的共生关系依赖于通过细菌类型3分泌系统(T3SS)分泌的类型3效应蛋白。在这里，我们报告了菌株NGR234的开放阅读框架y4zC编码一种新的根瘤菌3型效应器，称为NOPT(结瘤外部蛋白T)。对NGR234和T3SS突变体分泌蛋白的分析表明，NOPT是通过T3SS分泌的。在大肠杆菌和人HEK 293T细胞中表达的NOPT具有自身蛋白降解活性。加工后的NOPT在N末端暴露了一个甘氨酸(G50)，预计在真核细胞中是肉豆蔻酰化的。具有C93、H205或D220(催化三联体)点突变的NOPT自身蛋白降解活性显著降低，表明NOPT是YopT-AvrPphB效应器家族的一种功能性蛋白酶。当在烟草植物中瞬时表达时，具有蛋白分解活性的NOPT会引起快速的过敏性反应。转化nopt的拟南芥植株出现黄化和坏死症状，表明具有细胞毒作用。用NGR234突变体衍生物接种试验表明，NOPT对菜豆(Phaseolus ual garis cv.)玉豆1号；非洲山毛豆)或负(狗牙根)。我们认为，NOPT相关的多态性可能参与了NGR234对特定寄主豆类植物的进化适应。
Establishment of symbiosis between certain host plants and nitrogen-fixing bacteria ("rhizobia") depends on type 3 effector proteins secreted via the bacterial type 3 secretion system (T3SS). Here, we report that the open reading frame y4zC of strain NGR234 encodes a novel rhizobial type 3 effector, termed NopT (for nodulation outer protein T). Analysis of secreted proteins from NGR234 and T3SS mutants revealed that NopT is secreted via the T3SS. NopT possessed autoproteolytic activity when expressed in Escherichia coli or human HEK 293T cells. The processed NopT exposed a glycine (G50) to the N terminus, which is predicted to be myristoylated in eukaryotic cells. NopT with a point mutation at position C93, H205, or D220 (catalytic triad) showed strongly reduced autoproteolytic activity, indicating that NopT is a functional protease of the YopT-AvrPphB effector family. When transiently expressed in tobacco plants, proteolytically active NopT elicited a rapid hypersensitive reaction. Arabidopsis plants transformed with nopT showed chlorotic and necrotic symptoms, indicating a cytotoxic effect. Inoculation experiments with mutant derivatives of NGR234 indicated that NopT affected nodulation either positively (Phaseolus vulgaris cv. Yudou No. 1; Tephrosia vogelli) or negatively (Crotalaria juncea). We suggest that NopT-related polymorphism may be involved in evolutionary adaptation of NGR234 to particular host legumes.