Light is a highly rich source of information from the surrounding environment. Beside variations, we all experience on land, light also changes in aquatic environments with the differential absorption of bands by water molecules and the presence of various organic and inorganic particles.
Sensing of light relies on photoreceptor proteins that absorb light of specific wavelengths and activate specific signalling cascades to adjust cell physiology accordingly.
Diatoms possess a palette of photoreceptors proteins. We have particularly investigated the Phytochrome photoreceptor family in diatoms. We have shown that they exhibit classical Red and Far-red light absorption spectra, but are able to trigger response beyond, in particular upon blue light. Given the variation of the underwater lightscape, phytochrome can act as an optical depth sensor.
Recently, thanks to a combination of approaches, we have unraveled the new role of a diatom phytochrome (DPH) in the photoacclimation of photosynthesis, which could represent an important adaptive value in highly variable environments. Investigations on the specific photosynthetic steps targeted by phytochrome regulation are ongoing.
We are also extending the characterization of DPH photophysical properties, mode of reconstitution and signalling cascades controlling diatom responses to light changes. The environmental relevance of photosensing is investigated through the analysis of environmental data, which, in turn, will be used to explore novel functions in an iterative dialogue between in situ observations and laboratory studies.