Description du sujet de thèse

Viroids infect plants and can cause important diseases in crops. However, they do not encode any proteins. Thus, all interactions with host cell machineries for replication and movement are RNA-mediated. To gain insights into viroid-host interactions, the localization and intra-/intercellular trafficking of viroid RNA will be detected and observed in vivo by using BglG and MS2 in vivo RNA labeling systems previously developed in the hosting team. These RNA labelling systems consist of tagging the viroid RNA with stem-loop aptamers that allow detection through specific binding of co-expressed RNA aptamer-binding proteins BglG / MS2-CP fused to GFP. Viroid RNA without stem-loop aptamers will be used as negative control. In addition, you will also apply a protein-independent RNA reporter system (3WJ-4 × Bro). Because modifications in viroid RNA can interfere with viroid infectivity, the modified viroid RNA will also be expressed by agroinfiltration, as has been done previously to study tobacco mosaic virus RNA.
The specific detection of viroid RNA will be confirmed by colocalization with a viroid-binding protein such as VIRP1 fused to RFP. The localization and trafficking of the viroid RNA-VIRP1 ribonucleoprotein (RNP) complexes will be determined by imaging the complexes together with cellular markers of membranes, cytoskeleton, nucleus, and plasmodesmata. Moreover, to identify additional host factors in vivo-associated with viroid RNA, the MS2 / BglG-tagged viroid RNA will be isolated together with associated proteins by affinity chromatography using GFP-affinity beads. The associated proteins will be identified using mass spectrometry and further studied for in vivo colocalization with VIRP1 and tagged viroid RNA, as well as for functional significance in viroid infection by reverse genetics.
This project offers essential knowledge and experience in plant-pathogen interactions, cell biology, molecular biology, genetics, and biophysics. The candidate will learn advanced techniques, including DNA cloning, biochemical characterization of protein-RNA complexes and their analysis by mass spectroscopy, in vivo fluorescence imaging and microscopy, Arabidopsis genetics, and plant virology. The candidate will also achieve training in writing and communication skills, and how to present results to different audiences.

Contexte de travail

The position is located at the IBMP in Strasbourg (France) and available for 36 months, starting in June-July 2025. The Institute of Plant Molecular Biology (IBMP; http://www.ibmp.cnrs.fr/?lang=en) is the largest CNRS research institute in plant science in France. It hosts 18 research teams and is known for its expertise in plant genomics, genetics, metabolism, biochemistry, cell biology, and molecular physiology.

The candidate will join the Marie Sklodowska-Curie Actions-Doctoral Network “ViroiDoc” funded within the framework of the Horizon Europe Programme. The aim of this network is to investigate viroids that cause crop losses in the millions of euros every year and affect crop yields and quality worldwide. ViroiDoc offers an international, multidisciplinary and cross-sectoral training program consisting of the individual research project, training by the doctoral school, and specific ViroiDoc network-wide training in scientific, technical, digital, entrepreneurial and transferable skills. For more information, visit www.viroidoc.eu.

The candidate will be registered at the Doctoral School of Life Sciences and Health of the University of Strasbourg (http://ed.vie-sante.unistra.fr/) which provides numerous training courses in technical and transversal skills (108 hours of training are mandatory). In the laboratory, the candidate will be supervised and trained by experienced postdocs and a follow-up committee will provide support during the thesis project.

Important: To be eligible for this post, the candidate must not have resided or carried out the main activity at an institution in France for more than 12 months during the 3 years immediately before the recruitment date.
Moreover, the candidate must have a Master degree in molecular and /or cell biology, be able to communicate in written and spoken English, and be interested in plant-pathogen interactions. The candidate should have experience in DNA cloning, analytical techniques (PCR, Westernblot, etc), and fluorescence microscopy. Previous experience in plant-pathogen interactions is a plus. The post involves visits to collaborating teams in Argentina, Greece (Crete) and Spain. The candidate should be willing to travel and work for up to one month in these countries.

For consideration, candidates must also apply to position DC4 at www.viroidoc.eu. Available candidates will be ranked and interviewed by a Viroidoc recruitment committee. For further information, visit www.viroidoc.eu. Applications must be submitted electronically using the form on the ViroiDoc website (www.viroidoc.eu). Call details and guidelines for applicants are available on the ViroiDoc website (www.viroidoc.eu).