Cloning of hemA from Rhizobium sp. NGR234 and symbiotic phenotype of a gene-directed mutant in diverse legume genera |
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Authors: | John Stanley David N. Dowling William J. Broughton |
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Affiliation: | (1) Université de Genève, L.B.M.P.S., 1, chemin de l'Imperatrice, CH-1292 Chambèsy-Genève, Switzerland |
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Abstract: | Summary The hemA gene which encodes -aminolaevulinic acid synthase (ALAS), was cloned and characterized from the broad host-range Rhizobium strain NGR234. A cosmid, identified by hybridization with the cloned gene of R. meliloti and complementation of an R. meliloti hemA mutant, was subcloned to yield a 5.5 kb fragment containing the entire NGR234 gene. A physical-genetic map was made and the interposon was introduced into a single EcoRI site which bisects the gene. The mutated gene was homogenotized into NGR234 to generate a hemA mutant, with a view to evaluating the role of rhizobial bacteroid ALAS activity for a wide variety of legume symbioses. The mutant strain formed an ineffective (Fix–) symbiosis with all tested host plants. These included tropical legumes that produce either indeterminate (Leucaena) or determinate (Desmodium, Macroptilium, Lablab, Vigna) root nodules.Abbreviations ALA -aminolaevulinic acid - ALAS aminolaevulinic acid synthase - Lb leghaemoglobin - Lb-haem haem moiety of leghaemoglobin |
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Keywords: | hemA Rhizobium NGR234 Mutant Symbioses |
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