Jiménez-Guerrero Irene, López-Baena Francisco Javier, Medina Carlos
Departamento de Microbiología, Universidad de Sevilla, Avenida de Reina Mercedes, 6, 41012 Sevilla, Spain.
Plants (Basel). 2023 May 28;12(11):2133. doi: 10.3390/plants12112133.
Rhizobia can establish mutually beneficial interactions with legume plants by colonizing their roots to induce the formation of a specialized structure known as a nodule, inside of which the bacteria are able to fix atmospheric nitrogen. It is well established that the compatibility of such interactions is mainly determined by the bacterial recognition of flavonoids secreted by the plants, which in response to these flavonoids trigger the synthesis of the bacterial Nod factors that drive the nodulation process. Additionally, other bacterial signals are involved in the recognition and the efficiency of this interaction, such as extracellular polysaccharides or some secreted proteins. Some rhizobial strains inject proteins through the type III secretion system to the cytosol of legume root cells during the nodulation process. Such proteins, called type III-secreted effectors (T3E), exert their function in the host cell and are involved, among other tasks, in the attenuation of host defense responses to facilitate the infection, contributing to the specificity of the process. One of the main challenges of studying rhizobial T3E is the inherent difficulty in localizing them in vivo in the different subcellular compartments within their host cells, since in addition to their low concentration under physiological conditions, it is not always known when or where they are being produced and secreted. In this paper, we use a well-known rhizobial T3E, named NopL, to illustrate by a multitask approach where it localizes in heterologous hosts models, such as tobacco plant leaf cells, and also for the first time in transfected and/or -infected animal cells. The consistency of our results serves as an example to study the location inside eukaryotic cells of effectors in distinct hosts with different handling techniques that can be used in almost every research laboratory.
根瘤菌可以通过定殖于豆科植物根部，诱导形成一种名为根瘤的特殊结构，从而与豆科植物建立互利共生关系。在根瘤内部，细菌能够固定大气中的氮。众所周知，这种共生关系的兼容性主要由细菌对植物分泌的类黄酮的识别决定，植物对这些类黄酮做出反应，触发细菌结瘤因子的合成，从而驱动结瘤过程。此外，其他细菌信号也参与了这种相互作用的识别和效率，如胞外多糖或一些分泌蛋白。在结瘤过程中，一些根瘤菌菌株通过III型分泌系统将蛋白质注入豆科植物根细胞的细胞质中。这些蛋白质被称为III型分泌效应蛋白（T3E），它们在宿主细胞中发挥作用，除其他任务外，还参与减弱宿主防御反应以促进感染，从而促成该过程的特异性。研究根瘤菌T3E的主要挑战之一是在体内将它们定位在宿主细胞内不同亚细胞区室的固有困难，因为除了它们在生理条件下浓度较低外，人们并不总是知道它们何时何地产生和分泌。在本文中，我们使用一种著名的根瘤菌T3E，名为NopL，通过多任务方法来说明它在异源宿主模型中的定位，如烟草植物叶细胞，并且首次在转染和/或感染的动物细胞中定位。我们结果的一致性为研究不同宿主中效应蛋白在真核细胞内的定位提供了一个例子，采用的不同处理技术几乎可以在每个研究实验室中使用。
