Submitted to: Biophysical Society
Publication Type: Abstract only
Publication Acceptance Date: 3/1/2011
Publication Date: 3/5/2011
Citation: Strahan, G.D., Nagahashi, G., Douds, D.D. 2011. Identification of some diterpenoids and hydroxy fatty acids from carrot root cell walls that stimulate the presymbiotic hyphal growth of AM fungi. Biophysical Society. 1:1. Interpretive Summary:
Technical Abstract: Arbuscular mycorrhizal (AM) fungi infect about 80% of all land plants (Smith and Read 1997). They are soil borne and establish a mutually beneficial symbiotic association with a host root after colonization. The fungal hyphae from a colonized root can more thoroughly explore the soil than the root system and thereby can provide mineral nutrients (notably phosphorus)that are not normally accessible by the roots, in exchange for sugars generated by the host plant via photosynthesis. For the fungus to successfully find a host root in the soil to colonize, the hyphae from a germinated spore must grow and branch in many directions and at times, a considerable distance. The growth of germinated spores of AM fungi has been previously shown to be stimulated by two chemical categories of compounds from plants: Flavonoids stimulate the overall hyphal length, sesquiterpenoids stimulate hyphal branch formation. A third type of presymbiotic AM fungal growth was discovered previously when the primary germ tube of Gigaspora gigantea grew toward a host root in an in vitro culture system. This morphological pattern showed long lateral branches forming off the primary germ tube and main secondary hyphae of a germinated fungal spore. In this study, carrot root cell walls were isolated and purified, thereby reducing the number of metabolites present and simplifying the confirmation analysis. NMR characterization and identification of the cell wall components utilized 1D and 2D 1H-NMR spectroscopy, including correlation experiments (COSY and TOCSY) and Diffusion Oriented SpectroscopY (DOSY). The DOSY experiment spectroscopically separated components in the extract mixture on the basis of their diffusion constants in methanol, and integration analysis of the fatty acid resonances in the DOSY spectra pointed to two primary fatty acids in this cell wall mixture. This is the first report that has identified diterpenoids and hydroxy fatty acids as key compounds from host roots which stimulate the presymbiotic growth of AM fungi.