Rapid regulation of excitation energy in two pennate diatoms from contrasting light climates

Abstract

Non-photochemical quenching (NPQ) is a fast acting photoprotective response to high light stress triggered by over excitation of photosystem II. The mechanism for NPQ in the globally important diatom algae has been principally attributed to a xanthophyll cycle, analogous to the well-described qE quenching of higher plants. This study compared the short-term NPQ responses in two pennate, benthic diatom species cultured under identical conditions but which originate from unique light climates. Variable chlorophyll fluorescence was used to monitor photochemical and non-photochemical excitation energy dissipation during high light transitions; whereas whole cell steady state 77 K absorption and emission were used to measure high light elicited changes in the excited state landscapes of the thylakoid. The marine shoreline species Nitzschia curvilineata was found to have an antenna system capable of entering a deeply quenched, yet reversible state in response to high light, with NPQ being highly sensitive to dithiothreitol (a known inhibitor of the xanthophyll cycle). Conversely, the salt flat species Navicula sp. 110-1 exhibited a less robust NPQ that remained largely locked-in after the light stress was removed; however, a lower amplitude, but now highly reversible NPQ persisted in cells treated with dithiothreitol. Furthermore, dithiothreitol inhibition of NPQ had no functional effect on the ability of Navicula cells to balance PSII excitation/de-excitation. These different approaches for non-photochemical excitation energy dissipation are discussed in the context of native light climate.Electronic supplementary materialThe online version of this article (10.1007/s11120-018-0558-0) contains supplementary material, which is available to authorized users.

Divergence of photosynthetic strategies amongst marine diatoms

“…Environments characterized by particularly large light fluctuations include shallow waters that are inhabited by both benthic diatoms and pelagic estuarine/coastal diatoms. Interestingly, the strategies used to deal with dynamic high light are quite different within niche-specific diatom groups, whereby non-motile benthic diatoms employ rapidly reversible nonphotochemical quenching through XC-presumably to cope with more variable light fields [8,40]-whereas motile benthic diatoms preferentially employ slower, sustained non-photochemical quenching [21,29]. This pattern has been further confirmed comparing Artic diatoms [41].…”

“…Diatoms exhibit varying responses to light to thrive across diverse environmental niches [40,41,101,[104][105][106]. Estuarine diatoms (e.g.…”

Differential Responses of Growth and Photochemical Performance of Marine Diatoms to Ocean Warming and High Light Irradiance

“…The photo-protection strategies found in marine phytoplankton that are used to deal with excess PAR are diverse. Diatoms employ an efficient xanthophyll cycle to dissipate excessive light energy (21) and cyanobacteria and other groups of algae can optimize energy distribution between the two photosystems via state transitions (41). However, phytoplankton also need additional mechanisms to cope with harmful UV radiation, since UV can directly damage the physical structure of photosynthetic organelles.…”

“…Therefore, the underlying mechanisms of photo-physiology in marine phytoplankton could be important in consideration of overall effects of climate change (20). Diatoms have several strategies to cope with high light or UV stress, for example, an active xanthophyll cycle, nonphotochemical quenching, state transitions and de novo synthesis of proteins to replace damaged subunits of PSII (21,22). Photochemical damage is independent of temperature, while the repair processes are mediated by enzymes and are thus sensitive to temperature rises.…”

Variations in abundance, diversity, photo-physiology and estimated productivity of micro-phytoplankton with depth at the Saya de Malha Bank, Mascarene Plateau

“…The diatom dissipates thermal energy via the xanthophyll cycle (Kashino and Kudoh, 2003). This is why diatoms have rapidly-inducible NPQ, and sustain high photochemical activities through a wide range of light intensities (Buck et al, 2019;Derks and Bruce, 2018).…”