Isolation, characterization, and structural elucidation of a “nod signal” excreted by Rhizobium trifolii ANU843 which induces root hair branching and nodule-like primordia in axenic white clover seedlings
Rhizobium excretes various metabolites which are biologically active on its leguminous host. For example, a substituted tetrasaccharide excreted by R. meliloti has been reported to induce alfalfa-specific root hair branching and control host specificity in this symbiosis (3). We study the excreted metabolites from the clover symbiont, R. trifolii, which are responsible for inducing the morphological changes that occur during infection and nodulation by this bacterial symbiont. We are particularly interested in the metabolites whose product ion/export require pSym nod genes; hence, these are called “nod signals”. Our general strategy has been to grow wild-type R. trifolii ANU843 on defined Bill medium with or without flavones to enhance nod gene expression, fractionate the culture supernatant, and perform axenic seedling bioassays on the purified excreted metabolites. Our results to date have shown that wild-type R. trifolii excretes a diversity of bacterial factors capable of affecting development of the root nodule symbiosis (1,2this paper, Fig. 1).
KeywordsRoot Hair White Clover Clover Root Root Hair Deformation Root Nodule Symbiosis
Unable to display preview. Download preview PDF.
- 1.Hollingsworth, R. I., Squartini, A., Philip-Hollingsworth, S., and Dazzo, F. (1989) in Signal Molecules in Plants and Plant-Microbe Interactions, ed. Lugtenberg, B. (Springer-Verlag, Berlin), pp. 387–393.Google Scholar
- 2.Hollingsworth, R. I., Squartini, A., Philip-Hollingsworth, S., and Dazzo, F. (1990) in Nitrogen Fixation: Achievements and Objectives. eds. Gresshoff, P., Roth, I., Stacey, G., and Newton, W. (Chapman and Hall, New York), in press, this book.Google Scholar