Transconjugants were mucoid (EPS+), and clover inoculated with the clones demonstrated symbiotic PF-6463922 clinical trial phenotypes similar to the wild type (Table 1). Table 1 rosR mutation affects symbiotic properties and EPS production of R. leguminosarum bv. trifolii 24.2. Defects are fully complemented by the wild-type rosR copy. Strain/plasmid

Nodule no. per planta Shoot weight (mg/plant)a EPS (mg/mg)b     (fresh wt) (dry wt)   Rt2440 5.1 ± 1.9 42.4 ± 11.4 4.3 ± 0.15 0.31 ± 0.03 Rt2441 6.2 ± 2.1 44.8 ± 10.2 4.9 ± 0.20 0.36 ± 0.04 Rt2472 4.9 ± 1.7 43.2 ± 7.7 4.2 ± 0.10 0.30 ± 0.03 Rt2440(pRC24) 12.3 ± 3.1 59.3 ± 12.5 6.1 ± 0.25 1.19 ± 0.07 Rt2441(pRC24) 12.5 ± 3.6 58.8 ± 10.2 6.0 ± 0.2 1.15 ± 0.05 Rt2472(pRC24) 12.7 ± 5.4 61.2 ± 14.2 6.2 ± 0.3 1.21 ± 0.06 Rt24.2 (wild type) 12.8 ± 2.9 62.8 ± 12.1 6.2 ± 0.25 0.97 ± 0.05 Uninoculated clover – 34.7 ± 6.4 3.8 ± 0.10 – a Plants were harvested 28 days after inoculation. Given values ( ± standard deviation) are averages of three independent experiments

with 20 plants for each treatment. b – Exopolysaccharide (EPS) production (Glc equivalents in mg/mg of protein). To study the check details competitive ability of the Rt2472 and the Rt2441 mutants, clover seedlings were inoculated with mixtures of each rosR mutant with Rt24.2 wild type in various proportions. For both mutants, in the case of a 1:1 strain ratio, the nodules were colonized buy GDC-0994 exclusively by the Rt24.2 wild type. In 10:1, 100:1, and 1000:1 strain mixtures, the percentage of nodules occupied by the Rt2472 mutant

was 1%, 2.5% and 9% of the sampled nodules, respectively (details not shown). The Rt2441 mutant demonstrated a similar decrease in competitiveness: the percentages of occupied nodules were 1%, 4.4%, and 11.1% in the 10:1, 100:1, and 1000:1 mixtures, respectively. The results indicated that rosR mutation substantially reduced the nodulation competitiveness of R. leguminosarum bv. trifolii 24.2. rosR mutants are altered in surface polysaccharides Non-mucoid colonies formed by the rosR mutants indicated Rucaparib cell line that the strains produced reduced amounts of surface polysaccharides. The amounts of EPS secreted by Rt2440, Rt2441 and Rt2472 were estimated to be about 30% of the amount formed by the wild type (Table 1). Rt2441, bearing a truncated rosR and an additional wild type copy of the gene, demonstrated the negative dominant nature of rosR mutation. To test the negative dominant effect on EPS production observed in Rt2441, plasmids containing different fragments of the regulatory region and rosR were constructed on pBBR1MCS backbone and introduced into Rt24.2 (Figure 2). The pEX1 plasmid containing the same fragment as in the Rt2441 mutant genome exerted a strong negative effect on EPS production, decreasing EPS synthesis to 54% of the control (Figure 2). Rt24.2(pEX8), containing exclusively the rosR upstream region with the RosR-box, produced 64% EPS of the wild type strain, but Rt24.