The Rhodococcus fascians-plant interaction: morphological traits and biotechnological applications

Abstract

Rhodococcus fascians is a Gram-positive bacterium that infects dicotyledonous and monocotyledonous plants, leading to an alteration in the normal growth process of the host. The disease results from the modulation of the plant hormone balances, and cytokinins are thought to play an important role in the induction of symptoms. Generally, on the aerial parts of the plants, existing meristems were found to be most sensitive to the action of R. fascians, but, depending on the infection procedure, differentiated tissues as well gave rise to shoots. Similarly, in roots not only actively dividing cells, but also cells with a high competence to divide were strongly affected by R. fascians. The observed symptoms, together with the determined hormone levels in infected plant tissue, suggest that auxins and molecules of bacterial origin are also involved in leafy gall formation. The complexity of symptom development is furthermore illustrated by the necessary and continuous presence of the bacteria for symptom persistence. Indeed, elimination of the bacteria from a leafy gall results in the further development of the multiple embryonic buds of which it consists. This interesting characteristic offers novel biotechnological applications: a leafy gall can be used for germplasm storage and for plant propagation. The presented procedure proves to be routinely applicable to a very wide range of plants, encompassing several recalcitrant species.

Taxonomy, Physiology, and Natural Products of Actinobacteria

“…Since then, the symptoms caused by R. fascians in diverse plant species have been described (reviewed by Goethals et al [517]). The bacterium infects both monocot and dicot hosts, many of which are economically important (518). Extensive epiphytic growth precedes intercellular invasion through stomata.…”

Chromosomal Locus That Affects Pathogenicity ofRhodococcus fascians

“…Moreover, the question of why mutant X798 showed an attenuated virulence remained. In the R. fasciansplant interaction, persistent and metabolically active bacteria are required to maintain the leafy gall structure (53). It was hypothesized that in planta the bacteria would grow on nutritional sources whose metabolism required a functional Mas.…”

“…It is a gram-positive actinomycete with a very broad host range, encompassing both monocots and dicots (3,53). It is a well-adapted epiphyte and grows on the surface of the plant as well as inside tissues (6).…”

Eternal Youth, the Fate of Developing Arabidopsis Leaves uponRhodococcus fasciansInfection

“…Altogether, these data support the role of CDKB1;1 in the progression over the G2/M checkpoint during the R. fascians-induced pathology and imply that CDKB1;1 is possibly a direct target for the R. fascians signals. The main virulence factors of R. fascians are the fas-encoded cytokinins (Crespi et al, 1992(Crespi et al, , 1994Vereecke et al, 2000;Pertry et al, 2009). Because cytokinins are known to directly regulate cell division at the G2-to-M transition by dephosphorylating CDKs (Zhang et al, 1996(Zhang et al, , 2005Laureys et al, 1998;Spíchal et al, 2007), besides stimulating CDKB1;1 expression, the direct activation of CDKs by the bacterial cytokinins might represent a second level of stimulation at the G2/M checkpoint.…”