Giulio Stella

Identification of novel regulator implicated in diatom growth and photosynthesis through reverse genetic approaches.

My research project is focussed on studying photosynthesis and photo protection in the diatom Phaeodactylum tricornutum. Diatoms are prominent marine micro algae which account for ~20% of oxygen production on the planet. Living in a turbulent environment, such as oceans, diatoms have to cope with ever changing light conditions (both for light intensity and light quality, i.e. colour), which is a very stressful situation for photosynthetic organisms. But diatoms have adapted to this kind of environment very well and are able to deal with stressing light conditions much better than land plants.

Diatoms can be used, in an applied research context, to produce high added value products (pigments, anti-oxidants) or biofuels (biodiesel). The understanding of their physiology and of the environmental conditions that promote or inhibit their growth is therefore of great industrial interest.

My project involves the production of different mutants with a modified photosynthetic apparatus to study diatoms' genetics and physiology. Photosynthesis is conducted in chloroplasts, small subunits of plant and diatom cells; thanks to Cellectis' know-how on genomic engineering, I can produce enzymes able to cut and modify DNA, called nucleases. With these enzymes I can introduce targeted mutations in specific genes involved in chloroplast activity in order to be able to better understand how these processes work.

In addition I will try to understand the connection between circadian rhythms and photosynthesis regulation: circadian rhythms are endogenous oscillations of biological processes that in animals control, for instance, sleeping time and appetite. In diatoms little is known about circadian regulation of photosynthesis and we will investigate if anticipation of day-to-night switch and vice-versa can help diatoms to increase their fitness and better regulate the components of their photosynthetic apparatus.

Since diatoms' physiology is still poorly understood these studies will help to improve our knowledge on the dynamic regulation of their photosynthetic apparatus. A better understanding of diatoms physiology will allow us to choose the best growing conditions and eventually to modify selected genes to increase biomass production and specific metabolite accumulation, such as pigments, anti-oxidants or lipids for biodiesel production. The final aim is in fact to increase of micro algae's performances in photobioreactors for industrial value products synthesis.