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Diatoms are a major class of phytoplankton, standing at the crossroads of several evolutionary lineages. They represent the most species-rich class of microalgae and are distributed worldwide, from tropical and subtropical regions to polar ecosystems. Thus, the diversity of diatom lifestyles and survival strategies can likely be attributed to their exceptional ability to adapt to diverse environments.

Light is the primary source of energy for photosynthetic organisms but also a key source of information on the surrounding environment. It is well established that diatoms have developed highly effective systems for optimizing light harvesting and energy generation from photosynthesis. Yet, little is known on the role of light sensing in the acclimation mechanisms, which synergistically control diatom cell growth and distribution within the ecological oceanic provinces they inhabit. To address these questions, we are performing integrated analyses of diverse but highly interconnected light-driven processes. By developing genomic and genetic resources for Phaeodactylum tricornutum, currently the most established experimental model for diatom molecular research, and by integrating genome-enabled and (eco)physiology approaches, we started to unveil new molecular players of diatom photoregulation. They include key regulators of photosynthesis and plastid photoprotection, photoreceptor variants, and a long-sought circadian clock controlling diatom responses to periodic light:dark cycles. Comparative functional investigations in diverse species and the analysis of the distribution of light regulators in the marine environment support hypothesis that light-driven processes are key players of diatom persistence. Providing new perspectives on how photoregulators evolved, diversified and act in aquatic environments strongly structured by light, these studies also highlight that integration of laboratory and environmental studies are both timely and essential to understand the life of algae in complex ecosystems.

Falciatore A, Jaubert M, Bouly JP, Bailleul B, Mock T. Diatom Molecular Research Comes of Age: Model Species for Studying Phytoplankton Biology and Diversity. Plant Cell. 2022, 32:547-572.

Falciatore A et al., Light-driven processes: key players of the functional biodiversity in microalgae. C R Biol. 2022 345(2):15-38

Falciatore A and Mock T Eds. “The Molecular Life of Diatoms” Book. Springer, 2022.