Réponses moléculaires du pommier et du poirier en interactions compatibles et incompatibles avec Erwinia amylorova, agent du fzu bactérien des maloideae

Erwynia amylorova est l'agent du feu bactérien, maladie du pommier et du poirier. Les déterminants du pouvoir pathogène de cette bactérie sont identifiés (hrp-dsp cluster, capsule, sidérophore) mais les mécanismes moléculaires conduisant à la maladie ou à la résistance ne sont toujours pas connus. Pour tenter de les élucider, nous avons entrepris de comparer les réponses de deux génotypes de pommier (connus pour leurs sensibilités contrastées au feu bactérien) confrontés à E. amylorova, des mutants du pouvoir pathogène de cette bactérie et le 1pathogène incompatible pseudomonas syringae pv. tabaci. Deux stratégies ont été utilisées : 1) l'analyse biochimique et moléculaire de différentes défenses candidates et 2) l'analyse de l'expression différentielle de gènes par cDNA-AFLP. Les résultats mettent en évidence trois sortes dé réponses : 1) des mécanismes sont élicités dans les deux génotypes par E. amylorova et P. s. pv tabaci, selon des cinétiques similaires (choc oxydant, protéines PR)RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Expression of a bacterial effector, harpin N, causes increased resistance to fire blight in Pyrus communis

http://dx.doi.org/10.1007/s11295-005-0006-0absen

Activation of three pathogen-inducible promoters of tobacco in transgenic pear (Pyrus communis L.) after abiotic and biotic elicitation.

International audienceIn order to improve pear resistance against fire blight caused by Erwinia amylovora, a search for promoters driving high-level expression of transgenes specifically in response to this bacterial pathogen has been undertaken. We have examined the ability of hsr203J, str246C and sgd24 tobacco (Nicotiana tabacum L.) promoters to drive expression of the uidA reporter gene in pear. Transgenic pear clones were obtained by Agrobacterium tumefaciens-mediated transformation. Beta-glucuronidase activity was determined quantitatively and qualitatively in these plants grown in vitro using fluorometric and histochemical assays and compared to cauliflower mosaic virus (CaMV) 35S promoter-driven activity. The hsr203J promoter appeared to be very weakly activated following inoculation in pear, which is the converse of the situation in tobacco. The str246C promoter was rapidly activated in pear during compatible and incompatible interactions, by wounding and following the application of several elicitors (capsicein, cryptogein, harpin, salicylic acid and jasmonic acid). The sgd24 promoter, a deletion derivative of str246C, exhibited a low level of expression after bacterial inoculation, was weakly activated by wounding and elicitors, and was not activated by phytohormones (salicylic acid and jasmonic acid). Interestingly, the sgd24 promoter was locally activated in pear, whereas the str246C promoter was activated systemically from the infection site. Taken together, these data show that, although the s tr246C and sgd24 promoters are less active than the CaMV35S promoter in pear, their pathogen-responsiveness would permit them to be used to drive the expression of transgenes to promote bacterial disease resistance

Caractérisation des WAKs (Wall associated Kinase) chez Populus et implication dans la réponse gravitropique

Communication oraleCette communication a reçu le Prix Pôle IAR de la meilleure communciation orale (RFP 2014).absen

Expression of bovine lactoferrin cDNA confers resistance to Erwinia amylovora in transgenic pear

International audienceThe siderophore produced by Erwinia amylovora, the causal agent of fire blight of Maloideae, is one of the virulence factors of this bacterium. The production of siderophores enables E. amylovora to overcome the conditions of iron limitation met in plant tissue, and may also protect the bacteria against active oxygen species produced through the Fenton reaction. In this paper, we have examined the ability of an iron chelator protein, encoded by the bovine lactoferrin gene, to reduce fire blight susceptibility in pear (Pyrus communis L.). Transgenic pear clones expressing this gene controlled by the CaMV35S promoter were produced by Agrobacterium tumefaciens mediated transformation. Transformants were analysed by RT-PCR and western blot to determine lactoferrin expression levels. Most transgenic clones demonstrated significant reduction of susceptibility to fire blight in vitro and in the greenhouse when inoculated by E. amylovora. These transgenic clones also showed a significant reduction of symptoms when inoculated with two other pear bacterial pathogens : Pseudomonas syringae pv. syringae and Agrobacterium tumefaciens. Moreover, we have shown that this increase in bacterial resistance was correlated with an increase in root ferric reductase level activity and leaf iron content. Despite negative effects on the growth of a few clones, our results indicate the potential of lactoferrin gene transformation to protect pear from fire blight through increased iron chelation

Leaf and Branch Hydraulic Plasticity of Two Light-Demanding Broadleaved Tree Species Differing in Water-Use Strategy

International audienceGlobal climate change creates new environmental scenarios and selective pressures; thus, a better understanding of the plasticity of plant functional traits is needed to predict how plant species will respond to shifts in climate. Among the important functional traits for plants are their hydraulic properties which ultimately determine their photosynthetic capacity, growth rate, and survival in a changing environment. In this study, the light sensitivity of leaf (KL) and branch hydraulic conductance (KB) to fast changes in irradiance, and hydraulic plasticity (PIh) was studied in two broadleaved tree species differing in water-use strategy-silver birch (Betula pendula) and hybrid aspen (Populus × wettsteinii). The KL increased by a factor of 3.5 and 1.5 from minimal values recorded in darkness to maximal values in high light conditions for birch and aspen, respectively, indicating a significantly higher PIh for birch (0.72) than for aspen leaves (0.35). KB increased 1.5fold from dark to light conditions for both species. The high light sensitivity of KL and KB provides a regulatory mechanism to maintain a balance between transpirational demand and hydraulic supply. The plasticity of these traits increases the ability of plants to cope with a rapidly changing environment and to adapt to global climate change

Creation of an integrated molecular dynamics workflow on the Galaxy platform : Characterization of aquaporin pores

International audienceGalaxy is an international bioinformatics platform for biologists [1] . So far, the Galaxy team has adapted molecular dynamics tools which are mainly tools to create the prerequisites of a simulation or to run a simulation. In our case, this simulation step was done but the tools to finalize our analysis were missing. This is why tools have been developed and integrated in Galaxy. This integration of a succession of internal tools in the form of a Galaxy workflow is intended to help biologists and would benefit from the high performance computing facilities connected to the Galaxy webservice.Tools developed here aim at studying the structure the structure of 102 aquaporin trajectories using a molecular dynamics approach. This approach requires to take into account the molecular scale (Ångströms) of the proteins and the time step (nanosecond). In total, we speak of a simulated trajectory of 100 ns to model the transport of a water molecule [2]. In order to optimize the computational time on a trajectory, each trajectory is divided into several sub-trajectories and the pore diameter calculations are performed for each sub-trajectory. The resulting data are then compiled in a table before being visualized in graphical form.This workflow is designed to work on aquaporin trajectories. Aquaporins are transmembrane proteins that transport water. In addition, an aquaporin is a tetramer composed of four protomers. Each protomer has six transmembrane alpha helices connected by extramembrane loops that structure into a central pore. In addition, each protomer is hourglass-shaped and has two sites consisting of 3 successive amino acids, Asparagine - Proline - Alanine (NPA) and an aromatic arginine site (arR) [3]. The NPA sites form an electro-static barrier preventing excess protons from entering the cell. The arR site is composed of 4 amino acids that form a constriction inside the pore of each protomer. This constriction prevents large particles from passing and also regulates the amount of water that can pass through the transmembrane space at any given time. Ourworlflow allows us to calculate the pore diameter at this constriction. Recent advances in pore diameter characterization of aquaporin complexes, from manipulation of molecular modeling files to visualization of results, will be presented here.References[1] V. Jalili et al., « The Galaxy platform for accessible, reproducible and collaborative biomedical analyses: 2020 up-date », Nucleic Acids Research, vol. 48, n o W1, p. W395-W402, juill. 2020, doi: 10.1093/nar/gkaa434.[2] R. O. Dror, R. M. Dirks, J. P. Grossman, H. Xu, et D. E. Shaw, « Biomolecular Simulation: A Computational Mi-croscope for Molecular Biology », Annu. Rev. Biophys., vol. 41, n o 1, p. 429-452, juin 2012, doi: 10.1146/annurev-biophys-042910-155245.[3] J.-S. Venisse et al., « Genome-Wide Identification, Structure Characterization, and Expression Pattern Profiling ofthe Aquaporin Gene Family in Betula pendula », IJMS, vol. 22, n o 14, p. 7269, juill. 2021, doi: 10.3390/ijms22147269

Resistance of sunflower to the biotrophic oomycete Plasmopara halstedii is associated with a delayed hypersensitive response within the hypocotyls

The biotrophic oomycete Plasmopara halstedii is the causal agent of downy mildew in sunflower. It penetrates the roots of both susceptible and resistant sunflower lines and grows through the hypocotyls towards the upper part of the seedling. RT-PCR analysis has shown that resistance is associated with the activation of a hsr203J-like gene, which is a molecular marker of the hypersensitive reaction in tobacco. Activation of this gene was specifically observed during the incompatible interaction and coincided with cell collapse in the hypocotyls. This HR was also associated with the early and local activation of the NPR1 gene which is a key component in the establishment of the SAR. No such HR or a significant activation of the hsr203J-like gene were observed during the compatible combination. These results suggest that the resistance of sunflower to P. halstedii is associated with an HR which fails to halt the parasite. By contrast, this HR triggers a SAR which takes places in the upper part of the hypocotyls and eventually leads to the arrest of parasite growth. A model describing the resistance of plants to root-infecting oomycetes is proposed

The involvement of a Wall Associated Kinase in the response to gravistimulation in poplar stems

PosterPlants are able to sense organ tilt and reorient their growth according to the gravity vector. In angiosperm woody species, the motor for the stem straightening in parts undergoing cambial growth is differential maturation between the two sides of the stem. The dynamics of the gravitropic response involved the sensing of the local inclination angle (gravisensing) as well as the sensing of the local curvature which progressively takes place in the straightening process (Bastien et al (2013). If one wants to specifically address the question of the gravisensing / graviresponse in plants undergoing secondary growth, the gravistimulation should not induce organ deformation. This is why we chose to tilt staked poplar trees in our experimental design. From this, one challenging research question is the identification of molecular actors specifically involved in gravisensing / graviresponse. Since it has been proposed that plant cells could sense gravity through the cytoskeleton-plasma membrane-cell wall continuum, wall associated kinases (WAK) with an extracellular part that can bind to pectins localized in the cell wall, appear as molecular candidates. Using in silico approaches, we showed that the WAK family in poplar is the largest characterized to date with 175 sequences. Gene expression was analyzed in various organs and tissues. Most WAKs were weakly expressed. Only 28 WAKs were expressed in the stem. One WAK is of particular interest showing differential expression after tilting of the stem. The protein was localized in young xylem and bark cells devoid of amyloplasts. These data suggest that a WAK could be involved in the sensing/response to gravistimulation in a manner independent of the displacement of amyloplats which is behind the starch-statolith hypothesis (Sack, 1997)