|Prome, Jean Claude|
Submitted to: International Journal of Mass Spectrometry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2002
Publication Date: 9/1/2002
Citation: Prome, J., Ferro, M., Debelle, F., Prome, D., Krishnan, H.B. 2002. The pivotal role of tandem mass spectrometry in structural determinations of nod factors produced by rhizobia. nod factors produced by wild-type strains of mesorhizobium huakii and rhizobium sp. mus 10. International Journal of Mass Spectrometry. 219(3):703-716. Interpretive Summary: Rhizobia are soil-dwelling bacteria that form nodules on the roots of legume plants. The nodules are specialized structures where atmospheric nitrogen is fixed by the bacterium, which in turn, is utilized by soybean plants for growth and development. This process is termed biological nitrogen fixation and it enables soybean plants to grow in nitrogen-poor soils. Nodule development involves the exchange of a series of molecular signals between plants and bacteria. Elucidation of the Nod factor structure is crucial to understanding the initial events in the nodulation process. In this study, we have determined the Nod factor structure of a rhizobium that is capable of forming nodules on both roots and stems. Information obtained from this basic study will help scientists understand the factors that limit the formation of nitrogen-fixing nodules. Such information should enable scientists to manipulate biological nitrogen fixation facilitating an increase in legume yields with minimal use of nitrogen fertilizers.
Technical Abstract: Nod factors, signal molecules secreted by rhizobium, play an important role in initiating the early events of nitrogen-fixing symbiosis. The core Nod factor structure common to rhizobial species consists of three to five N-acetyl glucosamine residues. Permutations of this basic structure include substitution of various N-linked acyl groups and addition of functional groups to sixth carbon of the pyranosyl ring. The plethora of molecular entities generated gives rise to host-bacteria specificity, as structural details are essential for recognition by plants and thus for activation of genes and synthetic pathways leading to the nodule formation. It is now possible to study Nod factors from low-producing wild-type bacterial strains with the use of mass spectrometry. We have demonstrated that Nod factors from the wild-type strain of Mesorhizobium huakii are similar to those generated by a genetically engineered over-producing strain of this organism. Rhizobium sp. mus 10 is a bacterium isolated from Indian soils that nodulate Sesbania, a tropical legume plant. Several Nod factors produced by this bacterial strain are identical to those produced by African strains that nodulate Sesbania species. However, two other Nod factors isolated from the Indian Rhizobium sp. mus 10 possessed unique structural features presumably acquired by evolutionary pressures in a different environment.