Structural and functional comparison of Frankia root hair deforming factor and rhizobia Nod factor

Abstract

The infectious processes of the Frankia-Alnus and Rhizobium-legume symbioses present strong similarities, suggesting the existence of analogies between Frankia root hair deforming factor and rhizobia Nod factors. Biochemical and functional analogies were tested using ACoN24d Frankia strain. The putative chitin-like nature of the Frankia deforming factor was explored by (i) gas chromatography coupled to mass spectrometry and thin layer chromatography, after radioactive labeling of the culture for detection of chitin oligomers, and (ii) following the root hair deforming activity of the supernatant after discriminating treatments (temperature, chitinase, butanol extraction). In parallel, the functional analogy was questioned by testing the mitotic activity of the Frankia supernatant onAlnus glutinosa (L.) roots. The implication in the symbiotic process of the Frankia factor was indirectly explored by testing the effect of a nodulation inhibitor (combined nitrogen) on root hair deformation. The studies of the combined nitrogen effect on root hair deformation indicate that the deformation induced in vitro by the Frankia factor is linked to the symbiotic process. Moreover, the various approaches used suggest that rhizobia Nod factors and Frankia root hair deforming factor are two structurally divergent symbiotic factors. However, functionnal differences between Frankia root hair factor and the Nod factors have to be confirmed.Key words: Frankia, root hair deforming factor, Nod factor, actinorhizal plants.

An update on research on Frankia and actinorhizal plants on the occasion of the 18th meeting of the Frankia-actinorhizal plants symbiosis

“…CcI3 (Chabaud et al 2016). This confirmed a previous study on a factor from Frankia ACoN24d (Ceremonie et al 1999). Interestingly, such diffusible active molecules were found to induce calcium spiking in C. glauca (Chabaud et al 2016) and in A. glutinosa (Granqvist et al 2015).…”

SymRK defines a common genetic basis for plant root endosymbioses with arbuscular mycorrhiza fungi, rhizobia, and Frankia bacteria

“…Part of this signaling cascade is also involved in transduction of the symbiotic signal in AM symbioses (5). This gave rise to the hypothesis that the evolutionarily recent legume-rhizobia symbiosis reuses some of the molecular mechanisms of the more ancient AM symbiosis (16 indicate only that the Frankia symbiotic signal is likely chemically different from NFs (10)(11)(12). Here, we report the isolation and characterization of CgSymRK, a SymRK/DMI2 homolog from the actinorhizal tree C. glauca.…”

“…Analyses of the genome of three Frankia strains (10), the biochemical characterization of a Frankia root hair-deforming factor whose chemical structure is unknown (11), and the failure of Frankia DNA to complement rhizobial nod gene mutants (12) (Fig. 1A).…”

Transcriptomics of Actinorhizal Symbioses Reveals Homologs of the Whole Common Symbiotic Signaling Cascade

“…Genome sequencing of Frankia revealed the absence of the canonical nod gene described in rhizobia (Normand et al, 2007a). Nevertheless, the Frankia root hair deformation signal shares functional similarities with the rhizobial Nod and fungal Myc factors, such as thermoresistance, a size below 1,400 D, sensitivity to some enzymes (Ceremonie, 1998), and hints that N-acetyl-D-glucosamine may be present (Ceremonie et al, 1999). Concerning the plant, numerous genes involved in the Nod factor signaling Figure 3.…”

“…A transcriptomic approach did not enable the detection of a symbiosis island of up-regulated genes (Alloisio et al, 2010). Conversely, Frankia is known to synthesize a heat-stable root hair-deforming factor (Ceremonie et al, 1999) as well as phenyl-acetate, an auxin that induces lateral root formation (Hammad et al, 2003;Perrine-Walker et al, 2010).…”