Publications by authors named "Pascal Ratet"

The emergence of commensalism and mutualism often derives from ancestral parasitism. However, in the case of rhizobium-legume interactions, bacterial strains displaying both pathogenic and nodulation features on a single host have not been described yet. Here, we isolated such a bacterium from Medicago nodules.

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The establishment of symbiotic interactions between leguminous plants and rhizobia requires complex cellular programming activated by Rhizobium Nod factors (NFs) as well as type III effector (T3E)-mediated symbiotic signaling. However, the mechanisms by which different signals jointly affect symbiosis are still unclear. Here we describe the mechanisms mediating the cross-talk between the broad host range rhizobia Sinorhizobium fredii HH103 T3E Nodulation Outer Protein L (NopL) effector and NF signaling in soybean.

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Mitigating pre-harvest sprouting (PHS) and post-harvest food loss (PHFL) is essential for enhancing food securrity. To reduce food loss, the use of plant derived specialized metabolites can represent a good approach to develop a more eco-friendly agriculture. Here, we have discovered that soybean seeds hidden underground during winter by Tscherskia triton and Apodemus agrarius during winter possess a higher concentration of volatile organic compounds (VOCs) compared to those remaining exposed in fields.

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Immunity and senescence play a crucial role in the functioning of the legume symbiotic nodules. The miss-regulation of one of these processes compromises the symbiosis leading to death of the endosymbiont and the arrest of the nodule functioning. The relationship between immunity and senescence has been extensively studied in plant organs where a synergistic response can be observed.

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Article Synopsis
  • Losses from disease and climate change significantly impact crop production, particularly cereals that supply 60% of human calories.
  • The study investigates how high carbon dioxide (hCO) levels affect plant immunity by growing a model cereal plant at various CO2 concentrations and examining its growth, pathogen resistance, and gene expression.
  • Results showed improved plant growth and increased metabolism-related gene expression at high CO2, alongside heightened immune responses, although there was also a complex susceptibility to pathogens despite no increase in fungal development.
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Wheat is one of the most important crops in the world. Its production can be influenced by a diversity of beneficial and pathogenic rhizospheric microbes, including fungi. Amongst them, beneficial spp.

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Soybean is a pivotal staple crop worldwide, supplying the main food and feed plant proteins in some countries. In addition to interacting with mutualistic microbes, soybean also needs to protect itself against pathogens. However, to grow inside plant tissues, plant defense mechanisms ranging from passive barriers to induced defense reactions have to be overcome.

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LEAFY plant-specific transcription factors, which are key regulators of flower meristem identity and floral patterning, also contribute to meristem activity. Notably, in some legumes, LFY orthologs such as Medicago truncatula SINGLE LEAFLET (SGL1) are essential in maintaining an undifferentiated and proliferating fate required for leaflet formation. This function contrasts with most other species, in which leaf dissection depends on the reactivation of KNOTTED-like class I homeobox genes (KNOXI).

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Medicago (Medicago truncatula) establishes a symbiosis with the rhizobia Sinorhizobium sp, resulting in the formation of nodules where the bacteria fix atmospheric nitrogen. The loss of immunity repression or early senescence activation compromises symbiont survival and leads to the formation of nonfunctional nodules (fix-). Despite many studies exploring an overlap between immunity and senescence responses outside the nodule context, the relationship between these processes in the nodule remains poorly understood.

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Medicago truncatula NODULE ROOT1 (MtNOOT1) and Pisum sativum COCHLEATA1 (PsCOCH1) are orthologous genes belonging to the NOOT-BOP-COCH-LIKE (NBCL) gene family which encodes key transcriptional co-regulators of plant development. In Mtnoot1 and Pscoch1 mutants, the development of stipules, flowers, and symbiotic nodules is altered. MtNOOT2 and PsCOCH2 represent the single paralogues of MtNOOT1 and PsCOCH1, respectively.

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Article Synopsis
  • Most major crop plants are polyploid and require the introduction of new traits through genetic engineering for better yields.
  • The study demonstrates that the MsNAC39 gene can be used to identify dominant mutations in tetraploid alfalfa, resulting in multifoliate leaves, which is highly desirable in breeding.
  • The authors propose using a combination of mutant libraries and CRISPR/Cas9 technology to efficiently discover beneficial traits and enhance the breeding of both self-pollinating and cross-pollinating polyploid crops.
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Article Synopsis
  • The study focuses on the essential NOOT-BOP-COCH-LIKE (NBCL) genes in grasses, particularly in barley, maize, rice, and brachypodium, which are crucial for vegetative and reproductive development.
  • Researchers used CRISPR-Cas9 techniques to create single and double mutants in Brachypodium distachyon to better understand the roles of two specific NBCL genes, BdUNICULME4 (CUL4) and BdLAXATUM-A (LAXA).
  • Results showed that these genes are vital for key developmental processes such as tillering, leaf patterning, and overall plant growth, and indicated complicated interactions between different NBCL genes in regulating these traits.
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In the environment microbes interact with plants and provide them with benefits that include protection against biotic and abiotic stresses as well as improved nutrition. However, plants are also exposed to parasites and pathogens. To manage appropriate responses, evolution has resulted in improved tolerance of plants to beneficial microbes while keeping the ability to recognize detrimental ones and to develop defense responses.

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The induction of plant somatic embryogenesis is often a limiting step for plant multiplication and genetic manipulation in numerous crops. It depends on multiple signaling developmental processes involving phytohormones and the induction of specific genes. The gene () is required for the production of plant embryogenic stem cells.

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Article Synopsis
  • Major traits in cultivated grasses like tillering, spike architecture, and seed shattering are influenced by NOOT-BOP-COCH-LIKE (NBCL) genes, which are important for development in key cereals like barley, maize, and rice.
  • This study focuses on the non-domesticated grass Brachypodium distachyon to analyze the NBCL genes BdUNICULME4 (CUL4) and BdLAXATUM-A (LAXA), which have homologous counterparts in other cereals.
  • The findings reveal that CUL4 is crucial for ligule and auricle development and influences tillering and spikelet activity, while LAXA negatively impacts tillering but positively affects spikelet development and floral
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Legumes have the capacity to develop root nodules hosting nitrogen-fixing bacteria, called rhizobia. For the plant, the benefit of the symbiosis is important in nitrogen-deprived conditions, but it requires hosting and feeding massive numbers of rhizobia. Recent studies suggest that innate immunity is reduced or suppressed within nodules [1-10]; this likely maintains viable rhizobial populations.

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A new study shows that plant receptor genes necessary for the ancient and widespread symbiosis with arbuscular mycorrhizal fungi were co-opted in legume plants, without modifications, to establish the evolutionarily more recent and more specific symbiosis with their bacterial rhizobium partners.

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The formation of nitrogen-fixing nodules on legume hosts is a finely tuned process involving many components of both symbiotic partners. Production of the exopolysaccharide succinoglycan by the nitrogen-fixing bacterium Sinorhizobium meliloti 1021 is needed for an effective symbiosis with Medicago spp., and the succinyl modification to this polysaccharide is critical.

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Rhodophiala bifida (R. bifida) is a representative of the Amaryllidaceae plant family and is rich in montanine, an alkaloid with high pharmaceutical potential. Despite the interest in these compounds, many steps of the biosynthetic pathway have not been elucidated.

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Objectives: The aim of this study was to develop a Trifolium pratense hairy root (HR) production protocol and select HR lines with high isoflavone yield following elicitor treatments.

Results: We obtained 13 independent HR lines, producing approximately three times more isoflavonoids than seedlings (3.3 mg/g dry weight) and in which 27 isoflavonoids were detected.

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Plants of the legume family host massive intracellular bacterial populations in the tissues of specialized organs, the nodules. In these organs, the bacteria, named rhizobia, can fix atmospheric nitrogen and transfer it to the plant. This special metabolic skill provides to the legumes an advantage when they grow on nitrogen-scarce substrates.

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Medicago truncatula is able to perform a symbiotic association with Sinorhizobium spp. This interaction leads to the formation of a new root organ, the nodule, in which bacteria infect the host cells and fix atmospheric nitrogen for the plant benefit. Multiple and complex processes are essential for the success of this interaction from the recognition phase to nodule formation and functioning, and a wide range of plant host genes is required to orchestrate this phenomenon.

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Article Synopsis
  • - The study focuses on the complex interactions between legume plants and rhizobia, specifically how certain genes contribute to the formation and maintenance of nitrogen-fixing nodules, which are essential for plant growth.
  • - Researchers identified a new gene that regulates indeterminate nodule identity, and its expression is significant during early nodule formation, predominantly in the nodule central meristem.
  • - Loss of function in key genes led to severe nodule identity loss, resulting in the formation of root-like structures that cannot support symbiotic rhizobia, shedding light on the molecular mechanisms of nodule development in legumes.
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