Submitted to: New Phytologist
Publication Type: Review Article
Publication Acceptance Date: 2/12/2001
Publication Date: N/A
Interpretive Summary: Mycorrhiza are symbiotic soil born fungi that colonize plant roots and supply the host plant with needed nutrients including phosphorus, nitrogen and trace metals. In return the plant provides the fungus with carbohydrate. In this relationship, crop plants produce higher yields on a lower input of fertilizer, are more resistant to pathogens and can tolerate estress more effectively. In this review we demonstrate how nuclear magnetic resonance (NMR) has played a key role in exploring the life cycle and various metabolic events of the mycorrhizal fungus. Using NMR spectroscopy a number of investigators have revealed a) the substrates used by mycorrhiza, b) the speciation of phosphorus compounds found in the fungus, c)the secondary metabolites produced in the fungus and d) the nitrogen and carbon metabolites transported and exchanged between the symbionts. A significant constraint on the use of NMR spectroscopy in vivo concerns the geometry of samples, so that in situ studies of intact mycorrhizas are not generally feasible and only excised tissues or axenically growing fungus have been studied. As with any method, some of the most exciting future contributions may be expected from the use of NMR spectroscopy in conjunction with other methods such as molecular genetic approaches, enzymology and cytohistochemical microscopy.
Technical Abstract: NMR studies of mycorrhizal symbioses have illuminated a number of functional aspects of these complex associations. In conjunction with isotopic labeling NMR is able to examine both in vivo and in vitro the transfer of substrates between the symbionts, as well as the production of secondary metabolites in response to colonization. In addition, this methodology is capable of determining the locations of the biosynthesis an translocations of storage compounds such as polyphosphates, lipids and carbohydrates in mycorrhizal fungi both in the free-living and in the symbiotic stages of their life cycle. NMR has been useful in analyzing metabolism, transport and energetics, and the results of such studies have practical and ecological significance. Models of transport and physiology to which NMR has contributed form the necessary foundation for functional genomic exploration.