Analysis of Glycine max and Galega orientalis Nodules Revealed Specific Features of Symbiotic Interface Organization in Determinate and Indeterminate Nodules.

During the development of legume-rhizobial symbiosis, the process of rhizobia internalization depends on the modification of the plant-microbial surfaces and, first of all, on the remodeling of cell walls of both plant cells and infection threads. The components of cell walls, intercellular matrix and plasma and symbiosome membranes in nitrogen-fixing nodules of two legume species belonging to different types—determinate (Glycine max L. Merrill) and indeterminate (Galega orientalis Lam.)—were studied. As a result, the localization and distribution of different types of pectins, fucosylated xyloglucans, cell wall proteins and arabinogalactan proteins were revealed. Species-specific features of the symbiotic interface were identified, namely the presence of the linear galactan side chain of rhamnogalacturonan I in the infection thread walls, the rhamnogalacturonan I backbone, Ca2+-linked homogalacturonan, and an increase in the labeling of low methylesterified homogalacturonan in the cell walls of uninfected cells in the indeterminate nodules of G. orientalis; the presence of the galactan side chain of rhamnogalacturonan I in the cell walls of uninfected cells and the predominant accumulation of fucosylated xyloglucan in the infection thread walls in the determinate nodules of G. max. In nodules of both species, arabinans (cross-linked with rhamnogalacturonan I and as part of arabinogalactan proteins) play a major role in the development of infection structures, in particular symbiosomes, namely, they are detected at early stages of symbiosome differentiation. [ABSTRACT FROM AUTHOR]