Five distinct cDNA clones for leghemoglobin (Lb) were isolated from pea (Pisum sativum) nodules. They were classified into two groups designated PsLbA and PsLbB according to sequence homology, O(2)-binding affinities of the recombinant proteins, and in situ localization of the mRNAs. The PsLbB group was comprised of four cDNA clones: PsLb120-1, -8, -29, and -34. They showed a high similarity of...

Nodules on the roots of legume plants host nitrogen-fixing Rhizobium bacteria. Several lines of evidence indicate that nodules are evolutionarily related to roots. We determined whether developmental control of the Medicago truncatula nodule meristem bears resemblance to that in root meristems through analyses of root meristem-expressed PLETHORA genes. In nodules, MtPLETHORA 1 and 2 are prefere...

Original Communications ß-Carboline Alkaloids from Ribes nigrum L. The deletion mutant Bradyrhizobium japonicum AP22 produces a structurally altered exo-polysaccharide. The nodulation of two cultivars each of Glycine max and Glycine soja, and cultivars of Macroptilium atropurpureum and Vigna radiata, infected with this mutant was examined in order to analyze the role of the exopolysaccharide in...

Nodules on the roots of legume plants host nitrogen-fixing Rhizobium bacteria. Several lines of evidence indicate that nodules are evolutionarily related to roots. We determined whether developmental control of the Medicago truncatula nodule meristem bears resemblance to that in root meristems through analyses of root meristem-expressed PLETHORA genes. In nodules, MtPLETHORA 1 and 2 are prefere...

All aerobic biological systems, including N(2)-fixing root nodules, are subject to O(2) toxicity that results from the formation of reactive intermediates such as H(2)O(2) and free radicals of O(2). H(2)O(2) may be removed from root nodules in a series of enzymic reactions involving ascorbate peroxidase, dehydroascorbate reductase, and glutathione reductase. We confirm here the presence of thes...

Parasponia is the first non-legume genus proven to form nitrogen-fixing root nodules induced by rhizobia. Infiltration with India ink demonstrated that intercellular air spaces are lacking in the inner layers of the nodule cortex. Oxygen must diffuse through these layers to reach the cells containing the rhizobia, and it was calculated that most of the gradient in O(2) partial pressure between ...

To study the global diversity of plant-symbiotic nitrogen-fixing Frankia strains, a rapid method was used to isolate DNA from these actinomycetes in root nodules. The procedure used involved dissecting the symbiont from nodule lobes; ascorbic acid was used to maintain plant phenolic compounds in the reduced state. Genes for the small-subunit rRNA (16S ribosomal DNA) were amplified by the PCR, a...

Based on localization and high activities of pyrroline-5-carboxylate reductase and proline dehydrogenase activities in soybean nodules, we previously suggested two major roles for pyrroline-5-carboxylate reductase in addition to the production of the considerable quantity of proline needed for biosynthesis; namely, transfer of energy to the location of biological N(2) fixation, and production o...

Mutualisms can be viewed as biological markets in which partners of different species exchange goods and services to their mutual benefit. Trade between partners with conflicting interests requires mechanisms to prevent exploitation. Partner choice theory proposes that individuals might foil exploiters by preferentially directing benefits to cooperative partners. Here, we test this theory in a ...