Project description:Nodulation Outer Protein P (NopP) and NopI of the type 3 secretion system (T3SS) of the rhizobium determine host specificity. Sinorhizobium fredii CCBAU25509 (R2) and CCBAU45436 (R4) have different NopP and NopI variants, affecting their respective symbiotic compatibilities with the cultivated soybean C08 and the wild soybean W05. Swapping the NopP variants between R2 and R4 has been shown to switch their compatibility with C08 with the rj2/Rfg1 genotype. To understand the effects of Nops on host compatibility, analyses on the transcriptomic data of W05 roots and nodules inoculated with S. fredii strains containing Nop variants uncovered many differentially expressed genes related to nodulation and nodule functions, providing important information on the effects of Nops on hosts and nodules.
Project description:Sinorhizobium fredii HH103 is a fast-growing rhizobial strain that is able to nodulate legumes that develop determinate nodules, e.g., soybean, and legumes that form nodules of the indeterminate type. Here we present the genome of HH103, which consists of one chromosome and five plasmids with a total size of 7.22 Mb.
Project description:Here we report that the structure of the Sinorhizobium fredii HH103 exopolysaccharide (EPS) is composed of glucose, galactose, glucuronic acid, pyruvic acid, in the ratios 5∶2∶2∶1 and is partially acetylated. A S. fredii HH103 exoA mutant (SVQ530), unable to produce EPS, not only forms nitrogen fixing nodules with soybean but also shows increased competitive capacity for nodule occupancy. Mutant SVQ530 is, however, less competitive to nodulate Vigna unguiculata. Biofilm formation was reduced in mutant SVQ530 but increased in an EPS overproducing mutant. Mutant SVQ530 was impaired in surface motility and showed higher osmosensitivity compared to its wild type strain in media containing 50 mM NaCl or 5% (w/v) sucrose. Neither S. fredii HH103 nor 41 other S. fredii strains were recognized by soybean lectin (SBL). S. fredii HH103 mutants affected in exopolysaccharides (EPS), lipopolysaccharides (LPS), cyclic glucans (CG) or capsular polysaccharides (KPS) were not significantly impaired in their soybean-root attachment capacity, suggesting that these surface polysaccharides might not be relevant in early attachment to soybean roots. These results also indicate that the molecular mechanisms involved in S. fredii attachment to soybean roots might be different to those operating in Bradyrhizobium japonicum.
