Meet the SPS PhD students – Axelle Deroubaix

Axelle Deroubaix, a graduate of the Master’s program in Plant Sciences, joined the “Effectors of Cellular Communication at the Fungal-Plant Interface” team at BIOGER (BIOlogy and Management of Phytopathogenic Fungi) in 2023, where she is pursuing her PhD under the supervision of Jean-Félix Dallery.

Tell us shortly about your project and why you are interested in this topic.

“ Colletotrichum higginsianum is a plant pathogen with a life cycle divided into two distinct phases. First, it colonizes an initial plant cell that is still alive (biotrophic phase) and feeds on the nutrients produced by the plant. Then, it kills the infected cell as well as neighboring cells (necrotrophic phase), allowing it to massively colonize the rest of the plant and produce spores to spread to nearby plants. Studies have shown that certain fungal genes, belonging to the family of enzymes involved in the biosynthesis of specialized metabolites, are specifically expressed during the biotrophic phase of infection. It is known that pathogens secrete molecules called effectors to hijack plant immune responses and thus complete their infectious cycle. However, the majority of reported effectors are proteins. The objective of my PhD is therefore to determine whether some gene clusters produce metabolites that play a role in subverting the plant’s immune responses. By generating mutant lines, I was able to identify a gene cluster in Colletotrichum higginsianum that is necessary for reducing the immune defenses of the host plant Arabidopsis thaliana during infection. Since this molecule was unknown, I then used a heterologous system to produce it in large amounts so that I could determine its structure and biosynthetic pathway, as well as conduct biological activity assays. Chemical analyses are currently being conducted in collaboration with the National Museum of Natural History in Paris.

I’m interested in this topic because it allows me to address fundamental aspects for understanding the mechanisms pathogens use to evade plant immunity. Furthermore, this multidisciplinary subject also helps broaden my knowledge, as many chemistry-related steps are carried out as part of my PhD.”

Why did you decide to work with plants? What do you like about plants?

“After high school, I studied Life Sciences at Paris-Cité University. There, I had the opportunity to explore animal physiology, but it was plant physiology that really caught my attention. What made me want to continue in this field was the contrast between what is observable and what happens at the microscopic level. Indeed, plants conceal an immense complexity of mechanisms designed to grow, produce sugar through photosynthesis, and, above all, constantly adapt to their surrounding environment. What truly sparked my passion for this field is the way plants are able to communicate with their environment and with one another, particularly in the context of immunity. Today, the topic that fascinates me is the study of the molecular dialogues established with the microorganisms in their environment, whether beneficial or pathogenic.”

How did being part of the SPS / Paris-Saclay Plant Sciences community contribute to your PhD?

“Being part of the SPS Plant Sciences research community has been a real plus for me. First of all,  I had the chance to teach in the workshop on plant-microorganism interactions of the PMB international master’s program, which belongs to the SPS network. This opportunity allowed me to discover the world of teaching and reinforced my belief that I truly enjoy sharing knowledge in plant biology. Furthermore, being part of the SPS network also allows me to engage in discussions with a large number of researchers across various branches of plant science. Indeed, the numerous SPS platforms and seminars provide a comprehensive understanding of concepts related to plant biology. »

What do you like the most about doing a PhD? Do you have a good memory to share?

“Doing a PhD is rewarding both professionally and personally. Since I found my internships in research laboratories so interesting, I decided to pursue a PhD in order to carry out a long-term project. What I enjoy most about my thesis project is, on the one hand, the biological question I’m trying to answer, and on the other hand, the variety of experiments to be conducted in the lab. In fact, my thesis revolves around techniques in molecular biology, microbiology, plant pathology, cytology, microscopy, biochemistry, and chemistry. For me, this multidisciplinary approach is a real opportunity, as it allows me to gain expertise in many aspects of biology and physiology. On a personal level, doing a PhD in bBiology teaches resilience and resourcefulness and fosters intellectual curiosity. Furthermore, the PhD is an experience that helps you understand teamwork, which is crucial in the world of research. I also met some wonderful people, and I will always have good memories of my years at BIOGER. My fondest memory from these three years will be the day my thesis advisors secured two ANR grants, one related to my project, which helped us overcome many funding-related obstacles, and the other related to another project, which enabled us to offer a PhD scholarship to an intern. »

What are your career goals after completing your PhD?

“After my PhD, I hope to continue in the world of academic research and would therefore like to pursue my career with a postdoctoral position abroad. Ideally, I’d like to continue working on topics related to plant-microbe interactions and plant immune defenses. Eventually, I plan to apply for permanent positions as a researcher or lecturer.”