The Rhizobium sp. BR816 nodO Gene Can Function as a Determinant for Nodulation of Leucaena leucocephala, Phaseolus vulgaris, and Trifolium repens by a Diversity of Rhizobium spp.

Abstract

Introduction of the subcloned nodO gene of Rhizobium sp. BR816 into R. meliloti 1021, R. leguminosarum bv. trifolii ANU843, and Azorhizobium caulinodans ORS571 significantly stimulated nodulation and infection of Leucaena leucocephala by these transconjugants. The BR816 nodO gene was also shown to suppress the nodulation defect of the nodU mutants of Rhizobium sp. NGR234 and R. tropici CIAT899 on L. leucocephala and of the nodE mutant of R. leguminosarum bv. trifolii ANU843 on white clover. Overproduction of NodO in BR816 extended its host range to Trifolium repens. While a Rhizobium sp. BR816 strain, mutated in nodO, had reduced nodulation and competitiveness on P. vulgaris, no altered phenotype was observed for this mutant on L. leucocephala. Analysis of the transcriptional activation of nodO in BR816 revealed enhanced expression in the presence of apigenin, under both aerobic and microaerobic conditions. Moreover, nodO was also expressed in the bacteroids of L. leucocephala nodules.

Infection and Invasion of Roots by Symbiotic, Nitrogen-Fixing Rhizobia during Nodulation of Temperate Legumes

“…With nodO overexpression the mutant no longer accumulated in large masses, some root hairs initiated infection threads, and some nodules formed. NodO protein is known to be secreted from bacterial cells, has been shown to form pores in membranes, and can be a host range determinant (180). It may be that NodO rescued the nodFEMNTLO phenotype by allowing ion flow across a root hair membrane and thus amplifying a weaker-than-normal signal transmitted by the stripped-down version of Nod factor.…”

Extracellular Glycanases of Rhizobium leguminosarum Are Activated on the Cell Surface by an Exopolysaccharide-Related Component

“…There are several other factors that are necessary for infection. In some rhizobia there is clear evidence for a role for the secreted signaling protein NodO (13,49) that forms cationselective pores in membranes and has been proposed to act on the plant plasma membrane (42). It appears that at least in some situations NodO plays a role in the establishment of infection events (20).…”

NolX of Sinorhizobium fredii USDA257, a Type III-Secreted Protein Involved in Host Range Determination, Is Localized in the Infection Threads of Cowpea ( Vigna unguiculata [L.] Walp) and Soybean ( Glycine max [L.] Merr.) Nodules

“…vicae (32,38). NodO, a secreted protein, forms pores in membranes and functions as a host range determinant (32,37). A nodFEMNTLO deletion mutant of R. leguminosarum bv.…”