Characterization of Rhizobium tropici ClAT899 Nodulation Factors: The Role of nodH and nodPQ Genes in Their Sulfation. Jorge L. Folch Mallol. (1) Department of Microbiology and Parasitology, University of Seville, 41012 Seville, Spain; (2) Department of Plant Molecular Biology, Institute of Biotechnology, U.N.A.M., Cuernavaca, Morelos 62271, Mexico. Silvia Marroquf (1), Carolina Sousa (1), Hamid Manyani (1), Isabel M. Lopez-Lara (4), Koen M. G. M. van der Drift (3), Johan Haverkamp (3), Carmen Quinto (2), Antonio Gil-Serrano (5), Jane Thomas-Oates (3), Herman P. Spaink (4), and Manuel Megfas(1). (1) Department of Microbiology and Parasitology, University of Seville, 41012 Seville, Spain; (2) Department of Plant Molecular Biology, Institute of Biotechnology, U.N.A.M., Cuernavaca, Morelos 62271, Mexico; (3) Department of Mass Spectrometry, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands; (4) Institute of Molecular Plant Sciences, Leiden University, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands; and (5)Department of Organic Chemistry, University of Seville, 41012 Seville, Spain. MPMI 9:151-163. Accepted 18 December 1995. Copyright 1996 The American Phytopathological Society.

We have purified and characterized the nodulation factors produced by Rhizobium tropici CIAT899. This strain produces a large variety of nodulalion factors, these being a mixture of sulfated or nonsulfated penta- or tetra-chito-oligosaccharides to which any of six different fatty acyl moieties may be attached to nitrogen of the nonreducing terminal residue. In this mixture we have also found methylated or nonmethylated lipo-chitin oligosaccharides. Here we describe a novel lipo-chitin-oligosaccharide consisting of a linear backbone of 4 N-acetylglucosamine residues and one mannose that is the reducing-terminal residue and bearing a C18:l fatty acyl moiety on the nonreducing terminal residue. In addition, we have identified, cloned, and sequenced R. tropici nodH and nodPQ genes, generated mutations in the nodH and nodQ genes, and tested the mutant strains for nodulation in Phaseolus and Leucaena plants. Our results indicate that the sulfate group present in wild-type Nod factors plays a major role in nodulation of Leucaena plants by strain CIAT899 of R. tropici. Hemos purificado y caracterizado los factores de nodulacion producidos por Rhizobium tropici CIAT899. Esta cepa produce una amplia variedad de factores de nodulation, siendo estos una mezcla de tetra- o penta-quito-oligosacaridos sulfatados o no sulfalados, a los cuales se puede unir un acido graso al nitrogeno del residuo terminal no reductor. En esta mezcla tambien hemos encon-trado lipo-quitin-oligosacaridos metilados y no metilados. Aqui describimos un nuevo lipo-quitin-oligosacarido que consiste en un esqueleto lineal de 4 residuos de N-acetil-glucosamina y una manosa como residuo terminal reduc- tor, y que porta un sustituyente acido graso C18:l en el residuo terminal no reductor. Ademas, hemos identificado, clonado y secuenciado los genes nodH y nodPQ de R. tropici, generado mutaciones en los genes nodH y nodQ y probado las cepas mutantes en cuanto a nodulalion en plantas de Phaseolus y Leucaena. Nuestros resultados indican que el grupo sulfato presente en los factores de nodulacion sil-vestres juegan un papel importante en la nodulacion de plantas de Leucaena por la cepa CIAT899 de R. tropici.