Auxin's Role in Symptom Dev't upon Rhodococcus fascians infection

Rhodococcus fascians is a bacterial pathogen of plants that affects plant growth and development. It infects plants through its virulence factors which are composed of hormones called cytokinins. Ghent University researcher Elisabeth Stes and colleagues conducted a study to elucidate the role of auxins in symptom development upon R. fascians infection in Arabidopsis.

The researchers conducted expression profiling of marker genes for auxin production and observed that cytokinins induce auxin production of plants by targeting the indole-3-pyruvic acid (IPA) pathway which leads to improved auxin signaling in infected tissues. Mutated Arabidopsis plants with defective IPA pathways showed less reaction to infection even if the bacterial colonization and virulence gene expression were not impaired.

These findings imply that plant-derived auxin was employed to stimulate symptom formation. The increased auxin production and cytokinin in infected plants changed the transport of auxins so that a new higher limit for auxin is set and distributed. This process is necessary for symptom onset and maintenance. The results provide scientists a model of action of bacterial and plant signals in Arabidopsis during infection of R. fascians.

Read the abstract at http://onlinelibrary.wiley.com/doi/10.1111/j.1365-313X.2011.04890.x/abstract.