NopL, an effector protein of Rhizobium sp NGR234, thwarts activation of plant defense reactions
NopL, an effector protein of Rhizobium sp NGR234, thwarts activation of plant defense reactions
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DOI：
10.1104/pp.103.031740
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发表时间：
2004-02-01
期刊：
影响因子：
7.4
通讯作者：
Staehelin, C
中科院分区：
文献类型：
--
作者：
Bartsev, AV;Deakin, WJ;Staehelin, C
通过细菌 III 型分泌系统递送至真核细胞的细菌效应蛋白是植物-病原体相互作用中的重要毒力因子。在与豆科植物形成共生、固氮关联的根瘤菌物种中发现了 III 型分泌系统。一种这样的细菌，根瘤菌。 NGR234 分泌许多 III 型效应子，包括结瘤外蛋白 L（NopL，以前称为 y4xL）。在这里，我们发现烟草（Nicotiana tabacum）中 nopL 的表达阻止了发病机制相关（PR）防御蛋白的完全诱导。表达 nopL 并感染马铃薯病毒 Y（坏死株 605）的转基因烟草植物仅表现出非常低水平的几丁质酶（I 类）和 β-1,3-葡聚糖酶（I 类和 III 类）蛋白。 Northern 印迹分析表明植物细胞中 nopL 的表达抑制 PR 基因的转录。乙烯处理抵消了 NopL 对几丁质酶（I 类）的影响。表达 nopL 的转基因莲花植物表现出发育延迟和低几丁质酶水平。体外实验表明，NopL 是植物蛋白激酶的底物。总之，这些数据表明，当 NopL 被递送到植物细胞中时，它会调节信号转导途径的活性，最终导致 PR 蛋白的激活。
Bacterial effector proteins delivered into eukaryotic cells via bacterial type III secretion systems are important virulence factors in plant-pathogen interactions. Type III secretion systems have been found in Rhizobium species that form symbiotic, nitrogen-fixing associations with legumes. One such bacterium, Rhizobium sp. NGR234, secretes a number of type III effectors, including nodulation outer protein L (NopL, formerly y4xL). Here, we show that expression of nopL in tobacco (Nicotiana tabacum) prevents full induction of pathogenesis-related (PR) defense proteins. Transgenic tobacco plants that express nopL and were infected with potato virus Y (necrotic strain 605) exhibited only very low levels of chitinase (class I) and beta-1,3-glucanase (classes I and III) proteins. Northern-blot analysis indicated that expression of nopL in plant cells suppresses transcription of PR genes. Treatment with ethylene counteracted the effect of NopL on chitinase (class I). Transgenic Lotus japonicus plants that expressed nopL exhibited delayed development and low chitinase levels. In vitro experiments showed that NopL is a substrate for plant protein kinases. Together, these data suggest that NopL, when delivered into the plant cell, modulates the activity of signal transduction pathways that culminate in activation of PR proteins.