Light-driven processes: key players of the functional biodiversity in microalgae

Abstract

Microalgae are prominent aquatic organisms, responsible for about half of the photosynthetic activity on Earth. Over the past two decades, breakthroughs in genomics and ecosystem biology, as well as the development of genetic resources in model species, have redrawn the boundaries of our knowledge on the relevance of these microbes in global ecosystems. However, considering their vast biodiversity and complex evolutionary history, our comprehension of algal biology remains limited. As algae rely on light, both as their main source of energy and for information about their environment, we focus here on photosynthesis, photoperception, and chloroplast biogenesis in the green alga Chlamydomonas reinhardtii and marine diatoms. We describe how the studies of lightdriven processes are key to assessing functional biodiversity in evolutionary distant microalgae. We also emphasize that integration of laboratory and environmental studies, and dialogues between different scientific communities are both timely and essential to understand the life of phototrophs in complex ecosystems and to properly assess the consequences of environmental changes on aquatic environments globally.

Hypometabolism to survive the long polar night and subsequent successful return to light in the diatom Fragilariopsis cylindrus

“…Diatom light‐harvesting pigments differ significantly from those of green algae and plants, and include chlorophyll c , fucoxanthin and the photoprotective pigments diadinoxanthin and diatoxanthin (Olaizola et al ., 1994) and also possess gene subfamilies encoding light‐harvesting complex proteins, LHCx and LHCz, believed to enhance photosynthetic light capture under variable environmental conditions (Goss & Lepetit, 2015). Furthermore, they are equipped with a suite of, sometimes unique, photoreceptors that finally regulate the sensing of the complex marine light climate to improve the global light acclimation (Falciatore et al ., 2022), including the cryptochrome photolyase family, which has both DNA repair and photoreceptor activities (Coesel et al ., 2009).…”

Biotechnological response curve of the cyanobacterium Spirulina subsalsa to light energy gradient

“…These parameters are interconnected: both spectral composition changes and PFD variations determine a change in total light energy, according to the different energy levels of the photons characterizing the different wavelengths (red, green, or blue). Microalgae are, therefore, adapted to cope with intricate changes through efficient signaling involving blue and red photoreceptors [ 13 – 17 ].…”