Hug Sebastian, Liu Yilei, Heiniger Benjamin, Bailly Aurélien, Ahrens Christian H, Eberl Leo, Pessi Gabriella
Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland.
Agroscope, Research Group Molecular Diagnostics, Genomics and Bioinformatics, Swiss Institute of Bioinformatics, Wädenswil, Switzerland.
Front Plant Sci. 2021 Jul 28;12:699590. doi: 10.3389/fpls.2021.699590. eCollection 2021.
STM815, a rhizobial strain of the family, is able to nodulate a broad range of legumes including the agriculturally important (common bean). harbors two type VI Secretion Systems (T6SS-b and T6SS-3) in its genome that contribute to its high interbacterial competitiveness and in infecting the roots of several legumes. In this study, we show that T6SS-b is found in the genomes of several soil-dwelling plant symbionts and that its expression is induced by the presence of citrate and is higher at 20/28°C compared to 37°C. Conversely, T6SS-3 shows homologies to T6SS clusters found in several pathogenic strains, is more prominently expressed with succinate during stationary phase and at 37°C. In addition, T6SS-b expression was activated in the presence of germinated seeds as well as in and root nodules. Phenotypic analysis of selected deletion mutant strains suggested a role of T6SS-b in motility but not at later stages of the interaction with legumes. In contrast, the T6SS-3 mutant was not affected in any of the free-living and symbiotic phenotypes examined. Thus, T6SS-b is potentially important for the early infection step in the symbiosis with legumes.
STM815是该菌属的一种根瘤菌菌株，能够使包括重要农作物菜豆（普通豆）在内的多种豆科植物结瘤。STM815在其基因组中含有两个VI型分泌系统（T6SS-b和T6SS-3），这有助于其在细菌间具有高竞争力并感染几种豆科植物的根。在本研究中，我们发现T6SS-b存在于几种土壤栖息植物共生体的基因组中，其表达受柠檬酸盐诱导，与37°C相比，在20/28°C时表达更高。相反，T6SS-3与几种致病菌株中发现的T6SS簇具有同源性，在稳定期和37°C时，在琥珀酸盐存在下表达更显著。此外，在萌发种子以及菜豆和豌豆根瘤存在的情况下，T6SS-b的表达被激活。对选定缺失突变菌株的表型分析表明，T6SS-b在运动性方面起作用，但在与豆科植物相互作用的后期不起作用。相比之下，T6SS-3突变体在所检测的任何自由生活和共生表型中均未受影响。因此，T6SS-b在与豆科植物共生的早期感染步骤中可能很重要。
