Diatoms are one of the key phytoplankton groups in the ocean, forming vast oceanic blooms and playing a significant part in global primary production. To shed light on the role of redox metabolism in diatom's acclimation to light–dark transition and its interplay with cell fate regulation, we generated transgenic lines of the diatom Thalassiosira pseudonana that express the redox-sensitive green fluorescent protein targeted to various subcellular organelles. We detected organelle-specific redox patterns in response to oxidative stress, indicating compartmentalized antioxidant capacities. Monitoring the GSH redox potential (EGSH) in the chloroplast over diurnal cycles revealed distinct rhythmic patterns. Intriguingly, in the dark, cells exhibited reduced basal chloroplast EGSH but higher sensitivity to oxidative stress than cells in the light. This dark-dependent sensitivity to oxidative stress was a result of a depleted pool of reduced glutathione which accumulated during the light period. Interestingly, reduction in the chloroplast EGSH was observed in the light phase prior to the transition to darkness, suggesting an anticipatory phase. Rapid chloroplast EGSH re-oxidation was observed upon re-illumination, signifying an induction of an oxidative signaling during transition to light that may regulate downstream metabolic processes. Since light–dark transitions can dictate metabolic capabilities and susceptibility to a range of environmental stress conditions, deepening our understanding of the molecular components mediating the light-dependent redox signals may provide novel insights into cell fate regulation and its impact on oceanic bloom successions.
Bibliographical noteFunding Information:
We are grateful to Dr. Daniella Schatz and Adva Shemi for the helpful discussions and comments on the manuscript. We thank Guy Schleyer for the graphic assistance. We thank Prof. Nils Kro€ger and Dr. Nicole Poulsen from the Center for Molecular Bioengineering at Technische Universitaet Dresden for assistance with the T. pseudonana transformation. We thank Dr. Ron Rotkopf from the Bioinformatics Unit at the Life Sciences Core Facilities, Weizmann Institute of Science for assisting with the statistical analysis. This research was supported by the Israeli Science Foundation (ISF) (grant no. 712233) awarded to AV.
© 2018 Phycological Society of America
- Thalassiosira pseudonana
- diurnal cycles
- redox signaling