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Dernière mise à jour : Mai 2018

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Offres de stage - Master

Offres de stage - Master
L'équipe IPN (Interactions Plantes-Nématodes) propose 2 offres de stages niveau Master

Analysis of the role of a miR164 in the formation of giant root cells induced by root knot nematodes

Contact : Stéphanie Jaubert-Possamai (stephanie.jaubert@inrae.fr) 0492386464

Root-knot nematodes are biotrophic endoparasitic worms responsible for major losses to global agriculture. A key step in the interaction between the plant and the root-knot nematode is nematode induction of giant plant cell formation in the infested root. In response to signals emitted by the nematode, cells of the root parenchyma will redifferentiate and turn into hypertrophied and multinucleate cells, called giant cells. The formation of these giant cells is the result of successive nuclear divisions without cell division and isotropic growth. The complete transcriptome assays performed in many plants have identified a large number of genes whose expression is altered in response to nematode infection. However, the mechanisms regulating the expression of genes in these giant cells remain unexplored to this day.

This project proposes to explore the mechanisms regulating this reprogramming of the gene expression involved in the formation of the giant cells of the plant. In recent years it has been clearly established that small non-coding RNAs play a key role in the regulation of gene expression in eukaryotes. In particular, microRNAs, non-coding RNA of about twenty nucleotides, induce a post-transcriptional repression strongly impacting the levels of gene expression.

To characterize the role of microRNAs in feeder cell formation, we analyzed microRNA populations in tomato feeder cells by high throughput sequencing. This approach allowed us to identify the miR164 miRNA family whose expression is modified during the formation of the feeder site. These differentially expressed microRNAs in galls are strong candidates for regulating giant cell formation.

The aim of the course is to characterize the function of the miRNA family of the plant during the response to root-knot nematode infection. This functional analysis of the miR164 family and the transcription factors respressed by miR164 involves 1) the characterization of the expression of the different members of the miR164 family as well as that of the targeted genes by quantitative PCR, 2) the localization of the expression of this miRNA family through confocal microscopic observation of transgenic plant roots expressing a fluorescent protein and finally 3) the study of the effect of modifying the expression of miR164 or their target on plant susceptibility to root-knot nematode with transgenic plants (tomato or Arabidopsis).

 Références Bibliographiques :

Medina C. et al. (2017) Characterisation of microRNAs from Arabidopsis galls highlights a role for miR159 in the plant response to the root-knot nematode Meloidogyne incognita. New Phytologist : 216(3):882-896. doi: 10.1111/nph.14717

Study of tetraspanins and vesicular trafficking in giant root cells induced by root knot nematodes

Contact : Stéphanie Jaubert-Possamai (stephanie.jaubert@inrae.fr) 0492386464

Tetraspanins are a family of transmembrane proteins and are markers of exosomes. In mammals, these proteins are involved in many pathologies and play a key role in various processes such as the spread of metastases in many cancers or the internalization of viral particles. In plants there are many tetraspanins, however their role remains very little known.

It has been very recently shown that tetraspanins are localized in exosome-like extracellular vesicle membranes in the model plant Arabidopsis thaliana. The small non-coding RNAs contained in these vesicles are delivered by the plant cell into phytopathogenic plant microorganisms in order to regulate their pathogenicity. Small RNAs and exosomes therefore seem to be major new players in plant defense.

Root-knot nematodes are biotrophic endoparasitic worms that initiate the formation of giant root cells in the infested plant. In response to signals emitted by the nematode, targeted cells will redifferentiate and transform into hypertrophied and multinucleate cells, called giant cells. The formation of these giant cells is the result of successive nuclear divisions without cell division and isotropic growth. The complete transcriptome assays performed in many plants have identified a large number of genes whose expression is altered in response to nematode infection. However, the mechanisms regulating the expression of genes in these giant cells remain unexplored to this day.

This project proposes to explore the role of exosomes and, more broadly, vesicular trafficking during the formation of giant plant cells in the plant Arabidopsis thaliana. Preliminary results from transcriptome analysis of infected Arabidopsis and tomato roots showed repression of tetraspanin gene expression in giant cell formation.

The intership will be organized in two axes: the first axis will aim to characterize the vesicular trafficking in giant feeding cells. For this, Arabidopsis transgenic plants expressing fluorescent markers specific for each type of vesicles (exosomes, endosomes, golgi, etc.) will be observed with a confocal microscope to describe the location and the behavior of the different types of vesicles. A second axis will use molecular biology techniques (DNA extraction and PCR) to characterize the repression of the tetraspanine 8 gene in the feeding cells that has previously demonstrated in the laboratory by sequencing strategy.

Références Bibliographiques :

Medina C. et al. (2017) Characterisation of microRNAs from Arabidopsis galls highlights a role for miR159 in the plant response to the root-knot nematode Meloidogyne incognita. New Phytologist : 216(3):882-896. doi: 10.1111/nph.14717

Medina C. et al. (2018) Characterization of siRNAs clusters in Arabidopsis thaliana galls induced by the root-knot nematode Meloidogyne incognita. BMC Genomics. 2018 Dec 18;19(1):943. doi: 10.1186/s12864-018-5296-3.