Scent of a Symbiont: The Personalized Genetic Relationships of Rhizobium—Plant Interaction

Abstract

Many molecular signals are exchanged between rhizobia and host legume plants, some of which are crucial for symbiosis to take place, while others are modifiers of the interaction, which have great importance in the competition with the soil microbiota and in the genotype-specific perception of host plants. Here, we review recent findings on strain-specific and host genotype-specific interactions between rhizobia and legumes, discussing the molecular actors (genes, gene products and metabolites) which play a role in the establishment of symbiosis, and highlighting the need for research including the other components of the soil (micro)biota, which could be crucial in developing rational-based strategies for bioinoculants and synthetic communities’ assemblage.

Sinorhizobium meliloti GR4 Produces Chromosomal- and pSymA-Encoded Type IVc Pili That Influence the Interaction with Alfalfa Plants

“…Successful establishment of this symbiosis results in the formation of root nodules, which are infected by bacteria that fix atmospheric dinitrogen into ammonia for direct use by the plant. The progress of this interaction entails different phases and a sophisticated molecular dialogue between the legume host and the rhizobial microsymbiont [ 1 , 2 , 3 ]. An early and crucial step for the establishment of symbiosis is the bacterial colonization of plant roots, a process that is initiated by the movement of rhizobia toward the plant root and is followed by bacterial attachment to the root surface and the development of a microbial community or biofilm [ 4 , 5 ].…”

Sinorhizobium meliloti DnaJ Is Required for Surface Motility, Stress Tolerance, and for Efficient Nodulation and Symbiotic Nitrogen Fixation

“…The development of nitrogen-fixing nodules in legume roots is the outcome of a complex process that involves a highly specific and continuous molecular dialogue between the two symbiotic partners, and of which much knowledge has been gained in the last years [ 1 , 4 , 5 , 6 ]. An early event crucial for the establishment of symbiosis is bacterial root colonization.…”

Editorial: Early signaling in the rhizobium-legume symbiosis

“…The formation of nitrogen-fixing nodules is a complex process in which bacterial infection needs to be co-ordinated with the nodule organogenesis program. This is achieved through a continuous molecular dialogue between the host plant and rhizobia, which leads to a high degree of specificity in the interaction with even strain- and host cultivar-dependent effects ( Cangioli et al., 2022 ). Much of that specificity is conferred by an exchange of signals that take place in the rhizosphere during the early stages of the association ( Roy et al., 2020 ).…”