Effect of Sinorhizobium fredii YC4 symbiotic plasmid amplification on nod factors and symbiotic N-fixation
费氏中华根瘤菌共生质粒扩增对结瘤因子组分和共生固氮能力的影响

Sinorhizobium fredii YC4 can form nitrogen-fixing nodules on soybean (Glycine max) and wild soybean (G. soja). It can produce unique lipochitooligosaccharide nod factors (LCOs), in comparison with the other four strains of S. fredii. The constitution of LCOs produced by YC4 contained more hydrophobic substitutions detected by Thin-layer chromatography (TLC) of 14C-labeled nod factors. A spontaneous mutant termed YSC3 amplified in the symbiotic plasmid was isolated from YC4, which can produce more amount of LCOs than its parental strain at 28 degrees C, and showed a difference in the construction of LCOs. Nodulation test indicated that YSC3 only formed ineffective nodules on soybean G. soja.