The Coexistence of Symbiosis and Pathogenicity-Determining Genes in Rhizobium rhizogenes Strains Enables Them to Induce Nodules and Tumors or Hairy Roots in Plants

Abstract

Bacteria belonging to the family Rhizobiaceae may establish beneficial or harmful relationships with plants. The legume endosymbionts contain nod and nif genes responsible for nodule formation and nitrogen fixation, respectively, whereas the pathogenic strains carry vir genes responsible for the formation of tumors or hairy roots. The symbiotic and pathogenic strains currently belong to different species of the genus Rhizobium and, until now, no strains able to establish symbiosis with legumes and also to induce tumors or hairy roots in plants have been reported. Here, we report for the first time the occurrence of two rhizobial strains (163C and ATCC11325T) belonging to Rhizobium rhizogenes able to induce hairy roots or tumors in plants and also to nodulate Phaseolus vulgaris under natural environmental conditions. Symbiotic plasmids (pSym) containing nod and nif genes and pTi- or pRi-type plasmids containing vir genes were found in these strains. The nodD and nifH genes of the strains from this study are phylogenetically related to those of Sinorhizobium strains nodulating P. vulgaris. The virA and virB4 genes from strain 163C are phylogenetically related to those of R. tumefaciens C58, whereas the same genes from strain ATCC 11325T are related to those of hairy root-inducing strains. These findings may be of high relevance for the better understanding of plant-microbe interactions and knowledge of rhizobial phylogenetic history.

Stress Tolerance and Symbiotic and Phylogenic Features of Root Nodule Bacteria Associated with Medicago Species in Different Bioclimatic Regions of Tunisia

“…Moreover, Velazquez et al (39) reported for the first time the occurrence of two strains (163C and ATCC 11325 T ) belonging to R. rhizogenes able to nodulate Phaseolus vulgaris. These strains displayed symbiotic plasmids carrying nod and nif genes phylogenetically related to those of E. meliloti.…”

Rooteomics: The Challenge of Discovering Plant Defense-Related Proteins in Roots

“…The pathogenic strains of this legume endosymbiont contain vir genes, which cause the formation of tumors or hairy roots [76]. Strains of R. rhizogenes were shown to be able to induce hairy roots or tumors in plants and also to nodulate P. vulgaris under natural environmental conditions [76].…”

“…The pathogenic strains of this legume endosymbiont contain vir genes, which cause the formation of tumors or hairy roots [76]. Strains of R. rhizogenes were shown to be able to induce hairy roots or tumors in plants and also to nodulate P. vulgaris under natural environmental conditions [76]. In M. truncatula, a time-course analysis of root protein profiles was investigated using 2-DE and MS identification after inoculation with the nitrogen fixing bacterium Sinorhizobium meliloti.…”

Phylogenetic assignment and mechanism of action of a crop growth promoting Rhizobium radiobacter strain used as a biofertiliser on graminaceous crops in Russia

“…However, no nif-like gene was discovered on the chromosome of A. tumefaciens strain C58 when the genome sequence of that bacterium was assembled. Nevertheless, recently, the coexistence of symbiosis and pathogenicity-determining genes has been shown to occur in strains of Rhizobium rhizogenes which enables them to induce nodules or tumours depending on plant species (Velá zquez et al 2005).…”