The relationship between virulence and cytokinin production by Rhodococcus fascians (Tilford 1936) Goodfellow 1984

Abstract

Qualitative and quantitative analyses were made of cytokinins secreted into liquid culture by virulent and avirulent strains of Rhodococcus fascians, and of the endogenous cytokinins in pea plants inoculated with the same strains. Both virulent and avirulent strains secreted a range of cytokinins into liquid culture. The nonhydroxylated cytokinins were present in the liquid cultures at levels up to 1000-fold higher than hydroxylated cytokinins, but the virulent strains secreted only slightly higher levels of isopentenyladenine (iP), isopentenyladenosine (iPA) and the tentatively identified methylthio-isopentenyladenosine (ms-iPA), than the avirulent strains. Pisum sativum cv. Novella plants that were inoculated with virulent strains contained only slightly higher levels of iP and ms-iPA but had lower levels of the cytokinin nucleotides than those plants that had been inoculated with the avirulent strains. The origin of the cytokinins secreted by avirulent and virulent strains is discussed, as is the significance of the cytokinin content of fasciated plants.

Methylated Cytokinins from the Phytopathogen Rhodococcus fascians Mimic Plant Hormone Activity

“…In ornamental plants, such infections reduce their value and contribute to economic losses worldwide (Putnam and Miller, 2007). Leafy gall symptoms are reminiscent of CK overproduction and can be partially induced by exogenous application of CKs (Thimann and Sachs, 1966;Eason et al, 1996). Although several CKs have been isolated from R. fascians culture filtrates, a clear correlation with pathogenesis is lacking partially owing to the low concentration of bacterial CKs (Eason et al, 1996).…”

“…Leafy gall symptoms are reminiscent of CK overproduction and can be partially induced by exogenous application of CKs (Thimann and Sachs, 1966;Eason et al, 1996). Although several CKs have been isolated from R. fascians culture filtrates, a clear correlation with pathogenesis is lacking partially owing to the low concentration of bacterial CKs (Eason et al, 1996). A synergistic action by a mixture of bacterially produced CKs has been proposed, leading to persistent accumulation of CKs locally .…”

Biosynthesis of Auxin by the Gram-Positive PhytopathogenRhodococcus fasciansIs Controlled by Compounds Specific to Infected Plant Tissues

“…The shooty phenotype induced by R. fascians on its host plants directed earlier studies toward the synthesis of cytokinins by this bacterium (2,18,24,28,48,51). Nevertheless, careful examination of the various symptoms resulting from R. fascians infection revealed that auxin could also play a role during the interaction with the plant (16,59).…”

“…On pFiD188 an isopentenyl transferase (ipt) homologue is located that is essential for symptom development and has been found in all virulent strains examined thus far (14,15,53). Moreover, it is known that R. fascians can produce at least 11 different cytokinins in vitro (2,18,24,28,48,51). In R. fascians, cytokinins probably originate from two sources, either release from tRNA (36, 38) and/or condensation of isopentenyl pyrophosphate and 5Ј-AMP (14).…”

“…In R. fascians, cytokinins probably originate from two sources, either release from tRNA (36, 38) and/or condensation of isopentenyl pyrophosphate and 5Ј-AMP (14). Nevertheless, hitherto no clear correlation between known cytokinins and symptom development could be established (16,18), suggesting that new cytokinin-like molecules could be involved in the formation of the leafy gall (23).…”