Ludovic Jami
Mediterranean Institute for Advanced Studies, IMEDEA, UIB-CSIC
Photosynthetic control of motility in microalgae
Microalgal photosynthesis and motility are of fundamental and technological interest, owing to their central role in the global oxygen cycle and their potential for biotechnological applications. Yet, the interplay between photosynthesis and motility in microalgae remains poorly understood, particularly the role of photosynthetic regulation in controlling motility. Here, we investigate this interplay in two species, Micromonas and Chlamydomonas reinhardtii.
Micromonas is a ubiquitous and ecologically important picoplanktonic alga (~2 µm). Although it lacks a dedicated light-sensing organelle, it exhibits light-responsive motility, suggesting a role for its photosynthetic apparatus in this response. By combining measurements of motility and photosynthetic activity, we in particular show that its motility response is triggered under optimal photosynthetic conditions.
Chlamydomonas reinhardtii is a model organism for both photosynthesis and motility, but too rarely studied to understand these two components together. We developed an experimental setup that allows us to stimulate independently the chloroplast and the eyespot, the light-sensing organelle responsible for phototaxis(i.e. their ability to move along light direction and gradient). This approach enables us to quantify the timescale and dynamics of photosynthetic regulation of phototaxis. Notably, we reveal bistable phototactic behaviour at the single-cell level and rationalize these observations using coupled reaction–transport equations.
Overall, our work paves the way towards identifying the mechanisms underlying photosynthetic regulation of microalgal motility and establishing an integrated view of these interconnected functions, which are crucial for light management and environmental adaptation.
