Departamento de Microbiología, Universidad de Sevilla, Avenida de Reina Mercedes, 6, 41012 Sevilla, Spain.
Int J Mol Sci. 2022 Sep 21;23(19):11089. doi: 10.3390/ijms231911089.
Rhizobia are soil bacteria that can establish a symbiotic association with legumes. As a result, plant nodules are formed on the roots of the host plants where rhizobia differentiate to bacteroids capable of fixing atmospheric nitrogen into ammonia. This ammonia is transferred to the plant in exchange of a carbon source and an appropriate environment for bacterial survival. This process is subjected to a tight regulation with several checkpoints to allow the progression of the infection or its restriction. The type 3 secretion system (T3SS) is a secretory system that injects proteins, called effectors (T3E), directly into the cytoplasm of the host cell, altering host pathways or suppressing host defense responses. This secretion system is not present in all rhizobia but its role in symbiosis is crucial for some symbiotic associations, showing two possible faces as Dr. Jekyll and Mr. Hyde: it can be completely necessary for the formation of nodules, or it can block nodulation in different legume species/cultivars. In this review, we compile all the information currently available about the effects of different rhizobial effectors on plant symbiotic phenotypes. These phenotypes are diverse and highlight the importance of the T3SS in certain rhizobium-legume symbioses.
根瘤菌是能够与豆科植物建立共生关系的土壤细菌。因此，在宿主植物的根部会形成根瘤，根瘤菌分化为能够将大气中的氮固定为氨的类菌体。氨被转移到植物中，以换取碳源和适合细菌生存的环境。这个过程受到严格的调控，有几个检查点来允许感染的进展或限制。III 型分泌系统（T3SS）是一种分泌系统，它将称为效应物（T3E）的蛋白质直接注入宿主细胞的细胞质中，改变宿主途径或抑制宿主防御反应。这种分泌系统并非存在于所有根瘤菌中，但它在共生中的作用对于某些共生关系至关重要，表现出两面性，就像 Dr. Jekyll 和 Mr. Hyde 一样：它可能是形成根瘤所必需的，也可能会阻止不同豆科植物/品种的结瘤。在这篇综述中，我们汇集了目前关于不同根瘤菌效应物对植物共生表型影响的所有信息。这些表型多种多样，突出了 T3SS 在某些根瘤菌-豆科植物共生中的重要性。
