Signaling in Legume–Rhizobia Symbiosis

Abstract

Legumes represent an important source of food protein for human nutrition and animal feed. Therefore, sustainable production of legume crops is an issue of global importance. It is well-known that legume-rhizobia symbiosis allows an increase in the productivity and resilience of legume crops. The efficiency of this mutualistic association strongly depends on precise regulation of the complex interactions between plant and rhizobia. Their molecular dialogue represents a complex multi-staged process, each step of which is critically important for the overall success of the symbiosis. In particular, understanding the details of the molecular mechanisms behind the nodule formation and functioning might give access to new legume cultivars with improved crop productivity. Therefore, here we provide a comprehensive literature overview on the dynamics of the signaling network underlying the development of the legume-rhizobia symbiosis. Thereby, we pay special attention to the new findings in the field, as well as the principal directions of the current and prospective research. For this, here we comprehensively address the principal signaling events involved in the nodule inception, development, functioning, and senescence.

Genomic Insights into the Symbiotic and Plant Growth-Promoting Traits of “Candidatus Phyllobacterium onerii” sp. nov. Isolated from Endemic Astragalus flavescens

“…A general screening was carried out for genes essential for promoting plant growth under different stresses. Several genes related to iron uptake (17), nitrogen metabolism (8), virulence, disease and defence (32), membrane transport (54), stress response (50), and sulfur metabolism (18) were found in strain IY22 (Table S5). The variety of habitats indicates that Phyllobacterium has acquired an impressive aptitude for adapting to its surroundings.…”

“…Rhizobia colonization is a crucial factor that affects the productivity of leguminous plants. These bacteria inhabit symbiotic nodules formed in the roots of leguminous plants [ 18 ]. The relationship between the bacteria and the legume in this symbiotic life is highly specific.…”

Omics approaches in understanding the benefits of plant-microbe interactions

“…Symbiotic associations involve intricate mechanisms that establish mutualistic relationships. Microbes synthesize signaling molecules, respond to host signals, regulate hormone pathways, and form specialized structures for nutrient exchange (Scaria and Ravi, 2023 ; Shumilina et al, 2023 ; Kaya, 2024 ; Koshila Ravi and Muthukumar, 2024 ). These mechanisms underscore the complexity of the symbiotic interactions between microbes and host plants.…”

Identification and functional analysis of recent IS transposition events in rhizobia

“…Rhizobia are alpha- and betaproteobacteria that, through the establishment of symbiotic interactions with leguminous plants, are able to fix atmospheric nitrogen as ammonium. As a result of this interaction, rhizobia induce the development of a specialized root structure, the nodule, where they differentiate into bacteroids with the ability to fix N2, providing the plant with a source of nitrogen in exchange for photosynthetic carbon mostly in the form of dicarboxylic acids (Gourion et al, 2015; Jones et al, 2007; Oldroyd et al, 2011; Poole et al, 2018; Shumilina et al, 2023). These bacteria are thus of particular interest due to their potential to improve crop yields and reduce the need for synthetic nitrogen fertilizers (Herridge et al, 2008).…”