The symbiotic interface in Pisum sativum L. and Rhizobium laguerreae interactions

Symbiotic interface plays a crucial role in symbiosis development and stability. In this study, the progressive remodeling of symbiotic interface components, such as pectins, arabinogalactan proteins, bacterial lipopolysaccharides, and others, were analyzed in pea (Pisum sativum L.) nodules induced with siх strains of Rhizobium laguerreae. Some strains induced effective nodules while others ineffective ones. The organization of the symbiotic interface in ineffective nodules differed from that in effective ones. Indeed, ineffective nodules were characterized by reduced pectin modification activity and lack of de-esterified homogalacturonan accumulation. Additionally, abnormal localization of arabinogalactan proteins, arabinogalactan protein-extensin, and callose was observed in response to certain rhizobia strains, indicating the involvement of these components in defense mechanisms during symbiosis. Transcriptome analysis of ineffective nodules revealed activation of plant defense responses and responses to the biotic stresses. Thus, abnormalities in the organization of the symbiotic interface were revealed, accompanying ineffective interaction of pea with R. laguerreae strains.