Medicago-Sinorhizobium-Ralstonia Co-infection Reveals Legume Nodules as Pathogen Confined Infection Sites Developing Weak Defenses

Benezech, Claire; Berrabah, Fathi; Jardinaud, Marie-Françoise; Scornet, Alexandre Le; Milhes, Marine; Jiang, Gaofei; George, Jeoffrey; Ratet, Pascal; Vailleau, Fabienne; Gourion, Benjamin

doi:10.1016/j.cub.2019.11.066

Cited by 27 publications

(14 citation statements)

References 50 publications

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“…AM symbiosis appears to be established at the cost of plant immunity; plants must limit defense responses from some tissues to promote symbiosis and yet maintain immunity in other tissues. In the legume-rhizobial symbiosis, nodules display a weak defense response upon pathogen infection, but in M. truncatula, this weakened defense response is limited to nodules (38), indicating a spatiotemporal suppression of MAMP-triggered immunity during symbiosis. In addition, it is known that pathogens can secrete different types of effectors to interfere with plant immunity (39,40).…”

Section: Discussionmentioning

confidence: 99%

Discriminating symbiosis and immunity signals by receptor competition in rice

Zhang

Dai

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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Plants encounter various microbes in nature and must respond appropriately to symbiotic or pathogenic ones. In rice, the receptor-like kinase OsCERK1 is involved in recognizing both symbiotic and immune signals. However, how these opposing signals are discerned via OsCERK1 remains unknown. Here, we found that receptor competition enables the discrimination of symbiosis and immunity signals in rice. On the one hand, the symbiotic receptor OsMYR1 and its short-length chitooligosaccharide ligand inhibit complex formation between OsCERK1 and OsCEBiP and suppress OsCERK1 phosphorylating the downstream substrate OsGEF1, which reduces the sensitivity of rice to microbe-associated molecular patterns. Indeed, OsMYR1 overexpression lines are more susceptible to the fungal pathogen Magnaporthe oryzae, whereas Osmyr1 mutants show higher resistance. On the other hand, OsCEBiP can bind OsCERK1 and thus block OsMYR1–OsCERK1 heteromer formation. Consistently, the Oscebip mutant displayed a higher rate of mycorrhizal colonization at early stages of infection. Our results indicate that OsMYR1 and OsCEBiP receptors compete for OsCERK1 to determine the outcome of symbiosis and immunity signals.

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Section: Discussionmentioning

confidence: 99%

Discriminating symbiosis and immunity signals by receptor competition in rice

Zhang

Dai

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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“…A recent study suggests that innate immunity is reduced or suppressed within nodules [ 75 ]. This reduction likely enables colonization and nodulation process and maintains viable rhizobia populations inside the plant.…”

Section: Sa In Plant–rhizobia Symbiosismentioning

confidence: 99%

“…This reduction likely enables colonization and nodulation process and maintains viable rhizobia populations inside the plant. Benezech and colleagues evaluated the potential consequences and risks associated with an altered immunity in the symbiotic organ [ 75 ]. They used a tripartite system with the model legume Medicago truncatula , its nodulating symbiont of the genus Sinorhizobium, and the pathogenic soil-borne bacterium Ralstonia solanacearum .…”

Section: Sa In Plant–rhizobia Symbiosismentioning

confidence: 99%

Salicylic Acid in Plant Symbioses: Beyond Plant Pathogen Interactions

Benjamin

Pandharikar

Frendo

2022

Biology

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Plants form beneficial symbioses with a wide variety of microorganisms. Among these, endophytes, arbuscular mycorrhizal fungi (AMF), and nitrogen-fixing rhizobia are some of the most studied and well understood symbiotic interactions. These symbiotic microorganisms promote plant nutrition and growth. In exchange, they receive the carbon and metabolites necessary for their development and multiplication. In addition to their role in plant growth and development, these microorganisms enhance host plant tolerance to a wide range of environmental stress. Multiple studies have shown that these microorganisms modulate the phytohormone metabolism in the host plant. Among the phytohormones involved in the plant defense response against biotic environment, salicylic acid (SA) plays an important role in activating plant defense. However, in addition to being a major actor in plant defense signaling against pathogens, SA has also been shown to be involved in plant–microbe symbiotic interactions. In this review, we summarize the impact of SA on the symbiotic interactions. In addition, we give an overview of the impact of the endophytes, AMF, and rhizobacteria on SA-mediated defense response against pathogens.

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“…Their specialized function -to host intracellular bacteria for nitrogen fixation -makes the conditions inside nodules unique. Nodules are immunocompromised compartments with an immune response that differs from the rest of the plant, but they are also confined and insulated from the root, allowing them to host large numbers of intracellular bacteria (91). Despite some distinguishing properties specific to different rhizobia and their plant hosts, all rhizobium-legume symbioses share some universal characteristics.…”

Section: Adaptations To Nitrogen Fixationmentioning

confidence: 99%

How Rhizobia Adapt to the Nodule Environment

2021

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Rhizobia are a phylogenetically diverse group of soil bacteria that engage in mutualistic interactions with legume plants. Although specifics of the symbioses differ between strains and plants, all symbioses ultimately result in the formation of specialized root nodule organs which host the nitrogen-fixing microsymbionts called bacteroids. Inside nodules, bacteroids encounter unique conditions that necessitate global reprogramming of physiological processes and rerouting of their metabolism. Decades of research have addressed these questions using genetics, omics approaches, and more recently computational modelling. Here we discuss the common adaptations of rhizobia to the nodule environment that define the core principles of bacteroid functioning. All bacteroids are growth-arrested and perform energy-intensive nitrogen fixation fueled by plant-provided C4-dicarboxylates at nanomolar oxygen levels. At the same time, bacteroids are subject to host control and sanctioning that ultimately determine their fitness and have fundamental importance for the evolution of a stable mutualistic relationship.

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Medicago-Sinorhizobium-Ralstonia Co-infection Reveals Legume Nodules as Pathogen Confined Infection Sites Developing Weak Defenses

Abstract: Highlights d M. truncatula nodules can be infected by the pathogenic bacterium R. solanacearum d M. truncatula nodules display weak defense reactions upon pathogen infection d R. solanacearum encounters confinement in M. truncatula nodules

Cited by 27 publications

References 50 publications

Discriminating symbiosis and immunity signals by receptor competition in rice

Discriminating symbiosis and immunity signals by receptor competition in rice

Salicylic Acid in Plant Symbioses: Beyond Plant Pathogen Interactions

How Rhizobia Adapt to the Nodule Environment

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