Joëlle Fournier's research while affiliated with Paul Sabatier University - Toulouse III and other places

Publications (21)

Article
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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 polysacc...
Article
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Mutualistic plant-microbe associations are widespread in natural ecosystems and have made major contributions throughout the evolutionary history of terrestrial plants. Amongst the most remarkable of these are the so-called root endosymbioses, resulting from the intracellular colonization of host tissues by either arbuscular mycorrhizal (AM) fungi...
Article
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During root nodule symbiosis, intracellular accommodation of rhizobia by legumes is a prerequisite for nitrogen fixation. For many legumes, rhizobial colonization initiates in root hairs through transcellular infection threads. In Medicago truncatula, VAPYRIN (VPY) and a putative E3 ligase LUMPY INFECTIONS (LIN) are required for infection thread de...
Chapter
Actinorhizal root nodules result from the interaction between a nitrogen-fixing actinomycete from the genus Frankia and roots of dicotyledonous trees and shrubs belonging to 25 genera within 8 plant families. Most actinorhizal plants can reach high rates of nitrogen fixation comparable to those found in root nodule symbiosis of the legumes. As a co...
Article
Nitrogen‐fixing filamentous Frankia colonize the root tissues of its actinorhizal host Discaria trinervis via an exclusively intercellular pathway. Here we present studies aimed at uncovering mechanisms associated with this little‐researched mode of root entry, and in particular the extent to which the host plant is an active partner during this pr...
Article
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Medicago truncatula is widely used as a model legume for symbiotic and pathogenic microbial interaction studies. Although a number of Agrobacterium-mediated transformation methods have been developed for M. truncatula, a rapid root transformation system was not yet available for this model plant. Here, we describe an easy method for rapid transgene...
Article
Full-text available
Legumes improve their mineral nutrition through nitrogen-fixing root nodule symbioses with soil rhizobia. Rhizobial infection of legumes is regulated by a number of transcription factors, including ERF Required for Nodulation 1 (ERN1). Medicago truncatula plants defective in ERN1 are unable to nodulate, but still exhibit early symbiotic responses i...
Article
Although it is now well-established that decorated lipo-chitooligosaccharide Nod factors are the key rhizobial signals which initiate infection/nodulation in host legume species, the identity of the equivalent microbial signaling molecules in the Frankia/actinorhizal association remains elusive. With the objective of identifying Frankia symbiotic f...
Chapter
Infection threads (ITs) are specialized apoplastic compartments formed within the epidermal and outer cortical root cells of leguminous host plants, whose role is to provide a confined transcellular route for the delivery of nitrogen-fixing symbiotic rhizobia to differentiating nodule tissues. IT construction is a progressive and tightly regulated...
Article
Full-text available
In many legumes, root entry of symbiotic nitrogen-fixing rhizobia occurs via host-constructed tubular tip-growing structures known as infection threads. Here we have used a confocal microscopy live-tissue imaging approach to investigate early stages of infection thread formation in Medicago truncatula root hairs expressing fluorescent protein fusio...
Article
Full-text available
Symbiosis between legume plants and soil rhizobia culminates in the formation of a novel root organ, the ‘nodule’, containing bacteria differentiated as facultative nitrogen-fixing organelles. MtNF-YA1 is a Medicago truncatula CCAAT box-binding transcription factor (TF), formerly called HAP2-1, highly expressed in mature nodules and required for no...
Article
The primary objective of this study was to identify the molecular signals present in arbuscular mycorrhizal (AM) germinated spore exudates (GSEs) responsible for activating nuclear Ca(2+) spiking in the Medicago truncatula root epidermis. Medicago truncatula root organ cultures (ROCs) expressing a nuclear-localized cameleon reporter were used as a...
Article
Full-text available
ABSTRACT Rhizobial Nodulation Factors (NF) activate a specific signaling pathway in Medicago truncatula root hairs (RHs) that involves the complex interplay of NSP1/NSP2 GRAS and ERN1 ERF transcription factors (TFs) to achieve full ENOD11 transcription. ERN1 acts as a direct transcriptional regulator of ENOD11 through the activation of the NF-respo...
Article
Ca(2+) spiking is a central component of a common signaling pathway that is activated in the host epidermis during initial recognition of endosymbiotic microbes. However, it is not known to what extent Ca(2+) signaling also plays a role during subsequent root colonization involving apoplastic transcellular infection. Live-tissue imaging using calci...
Article
* • The aim of this study was to investigate Ca2+ responses to endosymbiotic arbuscular mycorrhizal (AM) fungi in the host root epidermis following pre-infection hyphopodium formation in both legumes and nonlegumes, and to determine to what extent these responses could be mimicked by germinated fungal spore exudate. * • Root organ cultures of both...
Article
Full text at: http://onlinelibrary.wiley.com/store/10.1111/j.1469-8137.2010.03464.x/asset/j.1469-8137.2010.03464.x.pdf?v=1&t=hhfztq2y&s=1afb716dc9b407e6fa6777a0512dae11152c547d • The aim of this study was to investigate Ca(2+) responses to endosymbiotic arbuscular mycorrhizal (AM) fungi in the host root epidermis following pre-infection hyphopodium...
Article
Full-text available
Lipochitooligosaccharide nodulation factors (NFs) secreted by endosymbiotic nitrogen-fixing rhizobia trigger Ca(2+) spiking in the cytoplasmic perinuclear region of host legume root hairs. To determine whether NFs also elicit Ca(2+) responses within the plant cell nucleus we have made use of a nucleoplasmin-tagged cameleon (NupYC2.1). Confocal micr...
Article
Full-text available
In temperate legumes, endosymbiotic nitrogen-fixing rhizobia gain access to inner root tissues via a specialized transcellular apoplastic compartment known as the infection thread (IT). To study IT development in living root hairs, a protocol has been established for Medicago truncatula that allows confocal microscopic observations of the intracell...

Citations

... Symbiosis signaling allows NF recognition, but evolved from and overlaps with a more ancient symbiosis with arbuscular mycorrhizal fungi (AMF) (9). Sustained oscillations in nuclear and perinuclear Ca 2+ are the core of symbiosis signaling, and allow receptor perception of LCOs at the root surface to activate symbiotic gene expression (10)(11)(12)(13)(14). The proteins responsible for symbiotic Ca 2+ oscillations reside on the nuclear membrane: the Ca 2+ -gated cation channels DMI1/POLLUX and CASTOR (15)(16)(17), three related cyclic nucleotide-gated channels (CNGC15s) (18), and the SERCA-type calcium ATPase (MCA8) (19). ...
... Among the analyzed 16 plant species, 10 species have 1-3 receptors in clade II (Table 3). LjEPR3 and MtLYK10 in this clade perceive exopolysaccharides from comparable and incomparable rhizobia to guide infection threads into the nodule (Kawaharada et al., 2015(Kawaharada et al., , 2017bMaillet et al., 2020). ...
... In particular, fungal release of tetrameric and pentameric CO is boosted upon strigolactone treatment (Genre et al., 2013). Furthermore, their activity has been demonstrated in legumes (Genre et al., 2013), carrot (Genre, Chabaud, Faccio, Barker, & Bonfante, 2008), rice (Carotenuto et al., 2017;Sun et al., 2015), Discaria trinervis and Casuarina glauca (Chabaud et al., 2019). ...
... To explore the utility of anthocyanin pigmentation as a visual marker for phenotyping of AMF symbiosis mutants, A. rhizogenes was used to induce pKPI-MtLAP1-transformed hairy roots in several mycorrhiza-defective M. truncatula mutants. RAM1 (Required for Arbuscular Mycorrhiza 1) is a GRAS transcription factor , DMI3 (Does not Make Infections 3) is a calcium/calmodulin-dependent protein kinase (L evy et al., 2004) and VPY (Vapyrin) is a protein that localizes to the tips of growing symbiotic infection structures (Zhang et al., 2015;Liu et al., 2019). Genes encoding all these proteins are essential for arbuscule formation (L evy et al., 2004;Pumplin et al., 2010;Murray et al., 2011;Gobbato et al., 2012). ...
... Frankia can possess two unmistakable environmental specialties, the land and root knotshaped on nonlegumes termed actinorhizal plant (Sellstedt & Richau, 2013). Actinorhizal plants have a place with 25 plant genera, for the most part trees and bushes (except for the lasting spice Datisca), addressing eight plant families Betulaceae, Casuarinaceae, Coriariaceae, Datiscaceae, Elaeagnaceae, Myricaceae, Rhamnaceae, and Rosaceae (Gherbi et al., 2019). ...
... Chapter 5 Frankia from actinorhizal plants amalgamated toward the promoter suspected of having associated with earlier host plante microorganism cooperation (Fournier et al., 2018). ...
... Agrobacterium-mediated transformation, as a powerful technique, is able to integrate several copies of the interesting gene into the host plant genome (Men et al., 2003;Remblière et al., 2018), but successful transformation depends on a lot of things such as the host plant; Agrobacterium strain; vector type; and inoculation, selection, and regeneration media (Lacroix and Citovsky, 2013). In this study, we observed lower callus multiplication in control treatment than in CX treatments, which may be due to the lack of phenolic compounds in the culture medium. ...
... In fact, simple mathematical models [57] propose explanations for decoding mechanisms based, among other features, on the number of spikes. Whereas Ca 2+ spiking stops before transcellular infection has finished [46], it lasts for the entire duration of bacterial progression through the infection thread at the root hair [54], with faster frequencies when the rate of elongation is more rapid. If the growth of the infection thread stops, nuclear Ca 2+ spiking is not observed [54]. ...
... Also, many chitinases are highly expressed in RH, which are known to regulate nod-factor levels (Malolepszy et al., 2018). Moreover, major transcriptional regulators of nodulation, ERN1 and 2, are preferentially expressed in RH and together work in the root epidermis to establish rhizobia infection (Cerri et al., 2016). The subset also includes LIN1 ligase that interacts with VPY1 and VPY2, and this interaction controls endocytosis for establishing rhizobia infection and interaction with arbuscular mycorrhizal fungi (Liu et al., 2021). ...
... The association between a nitrogen-fixing filamentous bacteria (Frankia) and a diverse range of trees and woody shrubs is less well characterized. However, a recent study found that a novel symbiotic factor from Frankia CcI3 strain was resistant to chitinase treatment and had relatively low molecular weight (i.e., in the range 0.5-5 KDa) (Chabaud et al., 2016). The novel symbiotic factor could trigger Ca 2+ spikes in root hairs and induce nodule inception (CgNIN) gene expression in the actinorhizal plant Casuarina glauca. ...