A comparison of chromosomal virulence genes in Agrobacterium rhizogenes A4, A. tumifaciens C58 and Rhizobium leguminosarum biovar trifolii.

摘要

A. tumefaciens is a plant pathogen that causes crown gall disease in dicotyledons. Governing pathogenesis are two important gene families: virulence (vir) genes, located on the plasmid, pTi, and chromosomal virulence (chv) genes, located on the circular chromosome. The role of the vir genes in Agrobacterium pathogenesis is well understood; however, the involvement of chv genes is less understood. This study focused on chvD, E, G, H and I. A. rhizogenes, a pathogen of dicotyledons with a method of infection similar to A. tumefaciens, stimulates plants to produce highly branched roots upon infection. chv and vir genes, located on the chromosomes and pRi, respectively, govern pathogenesis. Through its symbiotic relationship with leguminous plants, R. leguminosarum forms nitrogen-fixing nodules on the roots of its host. Those genes found on the symbiotic plasmid, pSym, are responsible for this symbiotic relationship. R. leguminosarum symbiosis closely resembles pathogenesis. We hypothesized that A. rhizogenes and R. leguminosarum will possess homologues to the chv genes of A. tumefaciens . (Abstract shortened by UMI.)