PhD project Colmar: Identification of the molecular mechanisms behind viral manipulation of plants to promote virus transmission by aphids

We are looking for a highly motivated student interested in insect vector behaviour and plant virology to apply for a PhD project described in detail below.

1. The student has to send a motivation letter (why you apply for that specific project), a CV including all marks and how he/she was ranked in masters to and We will then make interviews and select the best candidate depending on the 1) probability that the student will be invited by the ED for the concours and 2) suitability for the project.

2. The selected student has to apply at the Ecole Doctorale (ED) des Sciences de la Vie et de la Sante in Strasbourg for the PhD project submitted by Dr. Véronique Brault.
For every project offered by the ED, only one student can apply. The ED will then invite the best 64 students (based on their marks and ranking) for an interview, the concours. The best 40 will then receive a fellowship from the ED to do a PhD for three years. More information at

11th June: Deadline for students to subscribe at the ED
20th June: Deadline to submit marks from the master (24th June for students outside Strasbourg).
25th June: ED selects who to invite to the concours,
8-10th July: Concours
12th July: Results of concours
1st October: Start of PhD

Criteria 1: What is needed from the applicant to be invited to the concours: Ranked within the top 10% of your master (you must be able to show this) and a mark >14, better >15.
Criteria 2: What we expect: High motivation, autonomy and communication skills. Knowledge on plant health, phytopathology and plant-insect interactions.

With the pesticides ban in Europe and the recurring emergence of insecticide resistance, the frequency of insect-borne viral diseases in agricultural landscapes is rising sharply. Plant viruses, for which more than 75% are transmitted by vectors, are already responsible for considerable damage in agriculture (~ one-third of economic losses), and their impact is set to increase due to restrictive sanitary measures and global climate change, which favor the spread of insect vectors.

Viruses can manipulate the phenotype of their host plants (odors, colors, metabolism, etc.) and the behavior of vectors (preference, feeding, dispersal, fitness, etc.) in ways that enhance their transmission, an adaptive mechanism known as « viral manipulation ». Some of the virus components responsible for these effects have been identified, notably in our laboratory, where we showed that the P6 protein of cauliflower mosaic virus [CaMV] was involved in the externalization of viral symptoms and favored sustained sap ingestions by vectors, and consequently the acquisition of viral particles (Chesnais et al., 2021). Conversely, the cellular and molecular determinants in the infected host plant responsible for vector manipulation are still unknown.

In order to identify the cellular pathways manipulated by viruses in the host plant, transcriptomic studies were recently carried out on Arabidopsis thaliana infected with two viruses with different modes of transmission, CaMV (non-circulative virus) and turnip yellows virus (TuYV, circulative virus), both efficiently transmitted by the aphid Myzus persicae. The study revealed strong virus-specific signatures (Chesnais et al., 2022), including deregulations that could be responsible for behavioral alterations of aphids on infected plants. Functional validation, necessary to confirm the role of the genes and pathways identified in the manipulation mechanisms, is however unfeasible in view of the several hundred candidate genes identified by this approach.

The aim of this thesis project is, therefore, to tackle the problem from a new angle. We will exploit the genetic diversity of host plants (a genotyped collection of natural accessions of A. thaliana) and take advantage of a high-throughput video-phenotyping technique of aphid behavior to identify functional loci (genes or genomic regions) by « Genome-Wide Association Study » (GWAS). This combination of techniques has already been successfully applied to identify resistance genes to the aphid M. persicae in Arabidopsis, but has never been used to address the molecular mechanisms underlying viral manipulation and transmission. Compared to transcriptomic analyses, this method will enable unbiased, and more targeted, identification of genes or pathways altered in the infected host plant and responsible for aphid behaviors that favor viral transmission. We hypothesize that the genes identified in the plant and the aphid responses will be specific to the viruses’ modes of transmission, which is why both CaMV and TuYV, with contrasted transmission modes, will be studied. Functional validation using transgenic Arabidopsis will be carried out on the best candidates to confirm their role in viral manipulation effects. Understanding the molecular basis of this mechanism could contribute to the development of new control methods based on the blockage, or inhibition, of virus transmission by their vectors, by affecting the vector’s behavior on infected plants.

Wished skills:
– Basic knowledge on plant health, phytopathology and plant-insect interactions;
– Interest in the development of image analysis tools;
– Experience with computer and statistical tools (R);
– Experience with cellular and molecular biology techniques (RT-PCR, cloning, VIGS, etc.) would be a plus.
The candidate will carry out experiments autonomously under controlled laboratory conditions. The candidate must be curious, meticulous and have good communication skills to interact effectively with team members.

Expertises which will be acquired during the training:
– Knowledge on plant/virus/vector interactions and viral transmission mechanisms;
– Skills in handling insects and studying their behavior;
– Skills in plant virology (ELISA, virus transmission, etc.), molecular biology (RT-PCR, cloning, VIGS, etc.);
– Skills in phenotyping techniques, R programming, statistical analysis, etc.
These skills can easily be mobilized for future employment, both in academic research and in more specific scientific fields (seed companies, technical institutes, etc.).

The PhD student would be based in Colmar supervised by Véronique Brault ( and co-supervised by Quentin Chesnais (
Krieger C., Halter D., Baltenweck R., Cognat V., Boissinot S., Maia-Grondard A., Erdinger M., Bogaert F., Pichon E., Hugueney P., Brault V., & Ziegler-Graff V. (2023). An Aphid-Transmitted Virus Reduces the Host Plant Response to Its Vector to Promote Its Transmission. Phytopathology®, 113(9), 1745–1760.

Chesnais Q., Golyaev, V., Velt A., Rustenholz C., Brault V., Pooggin M. M., & Drucker M. (2022). Comparative plant transcriptome profiling of Arabidopsis thaliana Col-0 and Camelina sativa var. Celine infested with Myzus persicae aphids acquiring circulative and noncirculative viruses reveals virus- and plant-specific alterations relevant to aphid feeding behavior and transmission. Microbiology Spectrum, 10(4), e0013622.

Chesnais Q., Verdier M., Burckbuchler M., Brault V., Pooggin M., Drucker M. (2021) Cauliflower mosaic virus protein P6-TAV plays a major role in alteration of aphid vector feeding behaviour but not performance on infected Arabidopsis. Molecular Plant Pathology, 1–10.

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