Sensing and Signalling in Diatom Responses to Abiotic Cues

Abstract

Diatoms are prominent microalgae that proliferate in a wide range of aquatic environments. Still, fundamental questions regarding their biology, such as how diatoms sense and respond to environmental variations, remain largely unanswered. In recent years, advances in the molecular and cell biology of diatoms and the increasing availability of genomic data have made it possible to explore sensing and signalling pathways in these algae. Pivotal studies of photosensory perception have highlighted the great capacity of diatoms to accurately detect environmental variations by sensing differential light signals and adjust their physiology accordingly. The characterization of photoreceptors and light-dependent processes described in this review, such as plastid signalling and diel regulation, is unveiling sensing systems which are unique to these algae, reflecting their complex evolutionary history and adaptation to aquatic life. Here, we also describe putative sensing components involved in the responses to nutrient, osmotic changes, and fluid motions. Continued elucidation of the molecular systems processing endogenous and environmental cues and their interactions with other biotic and abiotic stress signalling pathways is expected to greatly increase our understanding of the mechanisms controlling the abundance and distribution of the highly diverse diatom communities in marine ecosystems.

A rapid aureochrome opto-switch enables diatom acclimation to dynamic light

“…We then sought for P. tricornutum photoreceptors important for its high light acclimation. Among the multiple photoreceptors encoded by the P. tricornutum genome, three proteins (AUREO1a, AUREO1b, and AUREO1c) belong to the stramenopile-speci c, blue light-sensing aureochrome family 63,64 .…”

Potential for the Production of Carotenoids of Interest in the Polar Diatom Fragilariopsis cylindrus

“…In temperate strains, red light is mainly sensed by phytochrome photoreceptors [ 73 ], and low fluences were proposed to help sensing the red wavelength-enriched surface of mixed water columns, and potentially higher light exposure [ 73 ], and were shown to trigger the photoprotective process (i.e., induction of the Ddx de-epoxidation and NPQ of ‘white’ light-acclimated cells [ 38 ]). While such roles can be questioned in F. cylindrus where no homologous phytochromes genes have been found so far [ 74 ], the long-term (several weeks) photoacclimatory response we observed points to a similar short-termed (4 days at max) higher red light dose in P. tricornutum [ 72 ]. We propose that this seemingly exacerbated response may be due to three non-exclusive facts.…”

The tonoplast localized protein PtNPF1 participates in the regulation of nitrogen response in diatoms

“…Then, in the Ptnpf1 knock‐out background, Pt54560 relative expression level after N repletion, although slightly reduced as compared to N starvation, is still significantly higher than in WT cells up to d5, suggesting that the mutants still prefer to transiently reallocate vacuolar NO 3 − rather than taking up the extracellular one. Since signalling pathways and ion fluxes are still poorly understood in diatoms (Smith et al ., 2019; Jaubert et al ., 2022; Helliwell, 2023), reconstructing these processes is one of the main challenges, as well as testing whether PtNPF1 could play a role in this context, similarly to what observed in higher plants' NPFs, acting as both sensors and transporters (Gojon et al ., 2011).…”