A new symbiotic cluster on the pSym megaplasmid of Rhizobium meliloti 2011 carries a functional fix gene repeat and a nod locus.

A 290-kilobase (kb) region of the Rhizobium meliloti 2011 pSym megaplasmid, which contains nodulation genes (nod) as well as genes involved in nitrogen fixation (nif and fix), was shown to carry at least six sequences repeated elsewhere in the genome. One of these reiterated sequences, about 5 kb in size, had previously been identified as part of a cluster of fix genes located 220 kb downstream of the nifHDK promoter. Deletion of the reiterated part of this fix cluster does not alter the symbiotic phenotype.

Ribulose 1,5-bisphosphate carboxylase. Effect on the catalytic properties of changing methionine-330 to leucine in the Rhodospirillum rubrum enzyme.

Oligonucleotide-directed mutagenesis of cloned Rhodospirillum rubrum ribulose bisphosphate carboxylase/oxygenase with a synthetic 13mer oligonucleotide primer was used to effect a change at Met-330 to Leu-330. The resultant enzyme was kinetically examined in some detail and the following changes were found. The Km(CO2) increased from 0.

Identification of a Rhizobium meliloti pSym2011 region controlling the host specificity of root hair curling and nodulation.

In Rhizobium meliloti 2011 nodulation genes (nod) required to nodulate specifically alfalfa are located on a pSym megaplasmid. Nod- derivatives carrying large pSym deletions were isolated. By complementation of these strains with in vivo- and in vitro-constructed episomes containing pSym of sequences and introduction of these episomes into Agrobacterium tumefaciens, we show (i) that from a region of pSym of about 360 kilobases, genes required for specific alfalfa nodulation are clustered in a DNA fragment of less than 30 kilobases and (ii) that a nod region located between nifHDK and the common nod genes is absolutely required for alfalfa nodulation and controls the specificity of root hair curling and nodule organogenesis initiation.

Activity expressed from cloned Anacystis nidulans large and small subunit ribulose bisphosphate carboxylase genes.

The ribulose bisphosphate carboxylase/oxygenase (EC4.1.1.