Journal Article

The Type VI Secretion System of Sinorhizobium fredii USDA257 Is Required for Successful Nodulation With Glycine max cv Pekin

Reyes‐Pérez, Pedro José, Civantos, Cristina, Ollero, Francisco Javier, Sánchez‐Reina, Ana, Bernal, Patricia, Pérez‐Montaño, Francisco, Jiménez‐Guerrero, Irene, Gandullo, Jacinto, Castro, Natalia Moreno‐de

2025

Overview

ABSTRACT The symbiotic relationship between rhizobia and legumes is critical for sustainable agriculture and has important economic and environmental implications. In this intricate process, rhizobial bacteria colonise plant roots and induce the formation of specialised plant organs, the nodules. Within these structures, rhizobia fix environmental nitrogen into ammonia, significantly reducing the demand for synthetic fertilisers. Multiple bacterial secretion systems (TXSS, Type X Secretion System) are involved in establishing this symbiosis, with T3SS being the most studied. While the Type 6 Secretion System (T6SS) is known as a “nanoweapon” commonly used by diderm (formerly gram‐negative) bacteria for inter‐bacterial competition and potentially manipulating eukaryotic cells, its precise role in legume symbiosis remains unclear. Sinorhizobium fredii USDA257, a fast‐growing rhizobial strain capable of nodulating diverse legume plants, possesses a single T6SS cluster containing genes encoding structural components and potential effectors that could target plant cells and/or act as effector‐immunity pairs. Our research reveals that this T6SS can be induced in nutrient‐limited conditions and, more importantly, is essential for successful nodulation and competitive colonisation of Glycine max cv Pekin. Although the system did not demonstrate effectiveness in eliminating competing bacteria in vitro, its active presence within root nodules suggests a sophisticated role in symbiotic interactions that extends beyond traditional interbacterial competition. The functional type VI secretion system of Sinorhizobium fredii USDA257 is required for successful nodulation with Glycine max cv Pekin.

• Publisher: John Wiley & Sons, Inc,John Wiley and Sons Inc,Wiley
• Subject: Agrochemicals / Ammonia / Bacteria / Bacterial infections / competition / E coli / Environmental impact / Flavonoids / Genes / Genetic engineering / Glycine max / Glycine max - microbiology / legume / Legumes / Metabolites / Nitrogen / Nodulation / Nodules / Plant cells / Plant Root Nodulation / Plant roots / Plasmids / Proteins / rhizobium / Root nodules / Sinorhizobium fredii / Sinorhizobium fredii - genetics / Sinorhizobium fredii - metabolism / Sinorhizobium fredii - physiology / Sustainable agriculture / Symbiosis / T6SS effectors / Toxins / type VI secretion system / Type VI Secretion Systems - genetics / Type VI Secretion Systems - metabolism