The tubulin cytoskeleton plays an important role in establishing legume–rhizobial symbiosis at all stages of its development. Previously, tubulin cytoskeleton organization was studied in detail in the indeterminate nodules of two legume species, Pisum sativum and Medicago truncatula. General as well as species-specific patterns were revealed. To further the understanding of the formation of general and species-specific microtubule patterns in indeterminate nodules, the tubulin cytoskeleton organization was studied in three legume species (Vicia sativa, Galega orientalis, and Cicer arietinum). It is shown that these species differ in the shape and size of rhizobial cells (bacteroids). Immunolocalization of microtubules revealed the universality of cortical and endoplasmic microtubule organization in the meristematic cells, infected cells of the infection zone, and uninfected cells in nodules of the three species. However, there are differences in the endoplasmic microtubule organization in nitrogen-fixing cells among the species, as confirmed by quantitative analysis. It appears that the differences are linked to bacteroid morphology (both shape and size).

In contrast to Rhizobium johnstonii strain 3841, R. johnstonii strain NaPi is able to form large pink nodules on the roots of pea ( Pisum sativum L.) mutants in the gene Sym40 . The genetic determinants underlying such efficiency have not been discovered yet. In this study, we report the complete genome sequence of the strain NaPi.

This report describes the genome sequence of Bradyrhizobium sp. strain RCAM1614, which was isolated from the root nodules of Lupinus angustifolius L. in the Leningrad district of Russia. The genome has a size of 9.77 Mbp and shows 96.1% completeness, which enables precise taxonomic classification.

The localization of different components of symbiotic interface were studied in allelic mutants of two key symbiotic pea genes, Sym33 and Sym40. Allelic mutants were characterized by similar distribution of most of the analyzed components. However, some specific allelic differences were identified. Among allelic mutants, the sym33-2 mutant exhibited the highest level of de-esterified homogalacturonan epitope labeled with the LM19 antibody, which coincided with the strongest defense responses in this mutant. Differences were also revealed in the distribution of rhamnogalacturonan branched galactan side chains (labeled with LM26) and fucosylated xyloglucan (labeled with CCRC-M1) in the nodules of the sym40-1 and sym40-2 mutants. The biological significance of these differences is not yet clear, since the sym40-2 mutation has not yet been identified.