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Phaseolus vulgaris Recognizes Azorhizobium caulinodans Nod Factors with a Variety of Chemical Substituents

¹F. A. Janssens Laboratory of Genetics, Catholic University of Leuven, Kardinaal Mercierlaan 92, B-3001 Heverlee, Belgium; ²Departamento de Genética Molecular, Centro de Investigación sobre Fijación de Nitrógeno, Universidad Nacional Autónoma de México, Ap. 565-A Cuernavaca, Morelos, Mexico; ³Laboratoire des Interactions Moléculaires et Réactivité Chimique et Photochimique, UMR 5623, Université Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse Cedex, France

Phaseolus vulgaris is a promiscuous host plant that can be nodulated by many different rhizobia representing a wide spectrum of Nod factors. In this study, we introduced the Rhizobium tropici CFN299 Nod factor sulfation genes nodHPQ into Azorhizobium caulinodans. The A. caulinodans transconjugants produce Nod factors that are mostly if not all sulfated and often with an arabinosyl residue as the reducing end glycosylation. Using A. caulinodans mutant strains, affected in reducing end decorations, and their respective transconjugants in a bean nodulation assay, we demonstrated that bean nodule induction efficiency, in decreasing order, is modulated by the Nod factor reducing end decorations fucose, arabinose or sulfate, and hydrogen.

Additional keywords: nodH, nodPQ.