Frankia BCU110501 diffusible factor(s) involved in Discaria trinervis nodulation, an intercellular root infected actinorhizal symbiosis.

GABBARINI L; WALL LG

Porto

Congreso; 16 International meeting on Frankia and actinorhizal plants; 2010

Frankia BCU110501, belonging to phylogenetic clade 3, induces nitrogen fixing root nodules in the Rosales actinorhizal plant Discaria trinervis via intercellular colonization, without root hair deformation. Frankia BCU110501 produces Diffusible Factors (DFs) which might be involved in early interactions with the Discaria trinervis roots, playing a role in the nodulation process. The induction of root nodule development in actinorhizal symbiosis would depend on the concentration of factors produced by the bacteria and the plant. A detailed analysis of nodulation kinetic revealed that those DFs produce changes at the level of initial rate of nodulation and also in nodulation profile. Diluted Frankia BCU110501 inoculum could be activated in less than 96 hours by DFs produced by Frankia BCU110501 cells previously washed. An attempt to biochemical characterization was carried out and showed that Frankia BCU110501 DFs would be of MW < 12kDa, negative charged at pH 7.0 and would contain a peptide bond necessary for its activity. Although Frankia BCU110501, belonging to Frankia Clade 3, does not induce nodules in Alnus acuminata, because of lack of full symbiotic recognition, it is able to deform root hairs as infective Frankia belonging to Clade 1 does. The root hair deforming activity of Frankia BCU110501 DFs show the same biochemical characteristics as the DFs involved in nodulation of Discaria trinervis, suggesting a basic structure for Frankia factors regardless the infection pathway activated in the interaction with the actinorhizal host plant.