Stella Césari: a ‘budding’ scientist recognised for her work in plant science

Plant immune receptors

Stella Césari, a post-doc researcher at INRA’s BGPI laboratory in Montpellier, France, is conducting research to better understand how plants recognize pathogens. She examines the molecular functions in immune receptors which allow plants to intercept molecules produced by pathogens when they infect a plant. These receptors act as a type of alarm system in plant cells, triggering defence mechanisms in the presence of a pathogen.

Her work has helped demonstrate that in plant cells, certain immune receptors form complexes within which a receptor acts as a sensor and intercepts the pathogen, while a second receptor triggers the immune response which produces plant resistance. She is the first to establish a model of how immune receptor pairs function in a cereal crop.

Identifying new mechanisms by which plants can resist disease is a major challenge in crop protection. Ms Césari’s thesis and post-doc research has allowed her to develop a model, together with other scientists in INRA’s Plant Health and Environment division, which shows how immune receptors in plants recognise pathogens: the “integrated decoy” model (see below).

Stella Césari has just received the “New Phytologist Tansley Medal for Excellence in Plant Science” This prestigious prize, awarded annually by the scientific journal New Phytologist, recognises the major contribution of a young scientist in the field of plant sciences. In Ms Césari’s case, the award highlights her work on intracellular immune receptors in plants, and her contribution to the discovery of “integrated decoy” domains in these receptors. The young researcher is naturally proud to receive this medal, but remembers to point out that the award is the ‘fruit’ of the team work of many researchers with whom she has been lucky enough to work in France and Australia.

A career in plants

Stella became interested in the living sciences during her secondary studies, after which she completed an internship at the University of Heidelberg as part of the “International Summer Science School Heidelberg” programme led by Professor Thomas Rausch, specialised in the molecular physiology of plants. This internship awoke a desire to study biology and become a researcher.

In 2009, Stella completed a Master’s degree in functional plant biology at the sciences faculty of Montpellier University. With an interest in plant/micro-organism interaction, developed over the course of her post-secondary studies, and as ever motivated by the idea of becoming a scientist, Stella passed the entrance exam to the doctoral programme at SIBAGHE (‘Integrated systems in biology, agronomy, geoscience, hydro-sciences, environment) in Montpellier, and obtained a Young Scientist Contract (CJS) from INRA. In 2009 she joined INRA’s BGPI laboratory in Montpellier, where she completed a thesis under the direction of Thomas Kroj and Jean-Loup Notteghem on the interaction between rice and Magnaporthe oryzae, the pathogenic fungus which causes rice blast, a disease which inflicts serious damage to the world’s rice production.

In 2013, Stella Césari obtained an INRA Young Scientist Contract (CJS) for a post-doctoral fellowship in Peter Dodd’s team at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Canberra (Australia) in the same field as her thesis work (functional molecular mechanisms in the immune receptors of rice), and on the activity of immune receptors involved in the resistance to powdery mildew in wheat.

After three and a half years of post-doctoral research with INRA and the CSIRO in Australia, Ms Césari decided to return to France in September 2016 to work on an ambitious engineering project involving immune receptors in rice.

Now 32, the young scientist has a long CV, and her recent award is the crowning achievement of many years’ work, investment and passion. In Stella’s view, being a researcher requires a lot of curiosity and creativity. She remains as motivated as ever, and believes that much remains to be discovered about the mechanisms behind a plant’s resistance and its sensitivity to pathogens. She would like to continue her research at INRA and further contribute to making progress in this field.

In detail : just what is an “integrated decoy”?

When a plant is infected, pathogens target proteins with an important role in a plant’s immune response, to inhibit these defence mechanisms or manipulate the host’s physiology to its benefit. Over the course of evolution, certain intracellular immune receptors have incorporated domains which look like the plant proteins targeted by pathogens. These domains, known as integrated decoys, allow these immune receptors to trap pathogens. If an integrated decoy detects the presence of a pathogen, an immune response is triggered which limits the spread of the infection.

The integrated decoy model has demonstrated the structural plasticity of intracellular immune receptors in plants, which makes it easier to engineer them. By modifying these integrated decoys, it becomes virtually possible to create “customised” immune receptors which give plants new types of resistance to a number of pathogens. The potential benefits for crop protection are considerable.

The integrated decoy model has also provided fundamental knowledge needed to identify the attack strategies of pathogens and predict which molecular mechanisms in the host are targeted during an infection. This knowledge can be used to identify new immune mechanisms in plants, as well as components which contribute to their sensitivity to pathogens.