Journal
PLANT PHYSIOLOGY
Volume 190, Issue 4, Pages 2295-2314Publisher
OXFORD UNIV PRESS INC
DOI: 10.1093/plphys/kiac455
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Funding
- National Key R&D Program of China [2018YFD0901500]
- Key Deployment Project of the Centre for Ocean Mega-Research of Science
- Chinese Academy of Sciences [COMS2019Q02, KLEMB-DYS02]
- Research Fund for the Taishan Scholar Project of Shandong Province [tspd20210316]
- Shandong Provincial RD Program [2018GHY115019]
- Distinguished Young Scientists Research Fund of the Key Laboratory of Experimental Marine Biology
- National Natural Science Foundation of China [41676157, 41976097]
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Diatoms express multiple genes under fluctuating light conditions in order to adapt to changing light environments. Prolonged preconditioning in severe light fluctuations enhances photosynthesis and carbon metabolism in diatoms, promoting their growth.
Unlike in terrestrial and freshwater ecosystems, light fields in oceans fluctuate due to both horizontal current and vertical mixing. Diatoms thrive and dominate the phytoplankton community in these fluctuating light fields. However, the molecular mechanisms that regulate diatom acclimation and adaptation to light fluctuations are poorly understood. Here, we performed transcriptome sequencing, metabolome profiling, and C-13-tracer labeling on the model diatom Phaeodactylum tricornutum. The diatom acclimated to constant light conditions was transferred to six different light conditions, including constant light (CL5d), short-term (1 h) high light (sHL1h), and short-term (1 h) and long-term (5 days) mild or severe light fluctuation conditions (mFL1h, sFL1h, mFL5d, and sFL5d) that mimicked land and ocean light levels. We identified 2,673 transcripts (25% of the total expressed genes) expressed differentially under different fluctuating light regimes. We also identified 497 transcription factors, 228 not reported previously, which exhibited higher expression under light fluctuations, including 7 with a light-sensitive PAS domain (Per-period circadian protein, Arnt-aryl hydrocarbon receptor nuclear translocator protein, Sim-single-minded protein) and 10 predicted to regulate genes related to light-harvesting complex proteins. Our data showed that prolonged preconditioning in severe light fluctuation enhanced photosynthesis in P. tricornutum under this condition, as evidenced by increased oxygen evolution accompanied by the upregulation of Rubisco and light-harvesting proteins. Furthermore, severe light fluctuation diverted the metabolic flux of assimilated carbon preferentially toward fatty acid storage over sugar and protein. Our results suggest that P. tricornutum use a series of complex and different responsive schemes in photosynthesis and carbon metabolism to optimize their growth under mild and severe light fluctuations. These insights underscore the importance of using more intense conditions when investigating the resilience of phytoplankton to light fluctuations. Diatoms use a series of complex and different responsive schemes in photosynthesis and carbon metabolism to optimize their growth under mild and severe light fluctuations.
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