Abstract
BackgroundDiatoms are able to acclimate to frequent and large light fluctuations in the surface ocean waters. However, the molecular mechanisms underlying these acclimation responses of diaotms remain elusive.ResultsIn this study, we investigated the mechanism of high light protection in marine diatom Thalassiosira pseudonana using comparative proteomics in combination with biochemical analyses. Cells treated under high light (800 μmol photons m−2s−1) for 10 h were subjected to proteomic analysis. We observed that 143 proteins were differentially expressed under high light treatment. Light-harvesting complex proteins, ROS scavenging systems, photorespiration, lipid metabolism and some specific proteins might be involved in light protection and acclimation of diatoms. Non-photochemical quenching (NPQ) and relative electron transport rate could respond rapidly to varying light intensities. High-light treatment also resulted in increased diadinoxanthin + diatoxanthin content, decreased Fv/Fm, increased triacylglycerol and altered fatty acid composition. Under HL stress, levels of C14:0 and C16:0 increased while C20:5ω3 decreased.ConclusionsWe demonstrate that T. pseudonana has efficient photoprotective mechanisms to deal with HL stress. De novo synthesis of Ddx/Dtx and lipid accumulation contribute to utilization of the excess energy. Our data will provide new clues for in-depth study of photoprotective mechanisms in diatoms.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3335-5) contains supplementary material, which is available to authorized users.
Highlights
Diatoms are able to acclimate to frequent and large light fluctuations in the surface ocean waters
These findings indicate that both the ML and high light (HL) can induce photoprotective responses in T. pseudonana
The results suggest that Lhcx4, Lhcx6, Lhcr5 and Lhcr8 are involved in photoprotection in T. pseudonana during HL stress
Summary
Diatoms are able to acclimate to frequent and large light fluctuations in the surface ocean waters. Eukaryotic phytoplankton that account for approximately 40% of the marine primary productivity, which makes them indispensable for marine food webs [1]. They play a vital role in nutrient recycling and climate regulation [1]. A number of physiological photoprotective mechanisms have evolved in various photosynthetic organisms to regulate photosynthesis under rapid light fluctuations. These mechanisms include the photosystem II (PSII) and PSI electron cycles, the fast repair of D1 protein of the PSII reaction center, the state-transitions, changes in the efficiency of energy shift from the harvesting complex to the reaction center, and non-photochemical quenching (NPQ) induced by activation of the xanthophyll cycle (XC) [5, 6].
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