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Response of CO2-starved diatom Phaeodactylum tricornutum to light intensity transition.

ABSTRACT: In this study, we investigated the responses of Phaeodactylum tricornutum cells acclimated to 300 µmol m-2 s-1 photon flux density to an increase (1000 µmol m-2 s-1) or decrease (30 µmol m-2 s-1) in photon flux densities. The light shift occurred abruptly after 5 days of growth and the acclimation to new conditions was followed during the next 6 days at the physiological and molecular levels. The molecular data reflect a rearrangement of carbon metabolism towards the production of phosphoenolpyruvic acid (PEP) and/or pyruvate. These intermediates were used differently by the cell as a function of the photon flux density: under low light, photosynthesis was depressed while respiration was increased. Under high light, lipids and proteins accumulated. Of great interest, under high light, the genes coding for the synthesis of aromatic amino acids and phenolic compounds were upregulated suggesting that the shikimate pathway was activated.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'.

SUBMITTER: Heydarizadeh P

PROVIDER: S-EPMC5516105 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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Response of CO2-starved diatom Phaeodactylum tricornutum to light intensity transition.

Heydarizadeh Parisa P Boureba Wafâa W Zahedi Morteza M Huang Bing B Moreau Brigitte B Lukomska Ewa E Couzinet-Mossion Aurélie A Wielgosz-Collin Gaëtane G Martin-Jézéquel Véronique V Bougaran Gaël G Marchand Justine J Schoefs Benoît B

Philosophical transactions of the Royal Society of London. Series B, Biological sciences 20170901 1728

In this study, we investigated the responses of Phaeodactylum tricornutum cells acclimated to 300 µmol m-2 s-1 photon flux density to an increase (1000 µmol m-2 s-1) or decrease (30 µmol m-2 s-1) in photon flux densities. The light shift occurred abruptly after 5 days of growth and the acclimation to new conditions was followed during the next 6 days at the physiological and molecular levels. The molecular data reflect a re ...[more]

PMID: 28717022

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Project description:BackgroundDiatoms (Bacilliariophyceae) encode two light-dependent protochlorophyllide oxidoreductases (POR1 and POR2) that catalyze the penultimate step of chlorophyll biosynthesis in the light. Algae live in dynamic environments whose changing light levels induce photoacclimative metabolic shifts, including altered cellular chlorophyll levels. We hypothesized that the two POR proteins may be differentially adaptive under varying light conditions. Using the diatom Phaeodactylum tricornutum as a test system, differences in POR protein abundance and por gene expression were examined when this organism was grown on an alternating light:dark cycles at different irradiances; exposed to continuous light; and challenged by a significant decrease in light availability.ResultsFor cultures maintained on a 12h light: 12h dark photoperiod at 200?E m-2 s-1 (200L/D), both por genes were up-regulated during the light and down-regulated in the dark, though por1 transcript abundance rose and fell earlier than that of por2. Little concordance occurred between por1 mRNA and POR1 protein abundance. In contrast, por2 mRNA and POR2 protein abundances followed similar diurnal patterns. When 200L/D P. tricornutum cultures were transferred to continuous light (200L/L), the diurnal regulatory pattern of por1 mRNA abundance but not of por2 was disrupted, and POR1 but not POR2 protein abundance dropped steeply. Under 1200?E m-2 s-1 (1200L/D), both por1 mRNA and POR1 protein abundance displayed diurnal oscillations. A compromised diel por2 mRNA response under 1200L/D did not impact the oscillation in POR2 abundance. When cells grown at 1200L/D were then shifted to 50?E m-2 s-1 (50L/D), por1 and por2 mRNA levels decreased swiftly but briefly upon light reduction. Thereafter, POR1 but not POR2 protein levels rose significantly in response to this light stepdown.ConclusionGiven the sensitivity of diatom por1/POR1 to real-time light cues and adherence of por2/POR2 regulation to the diurnal cycle, we suggest that POR1 supports photoacclimation, whereas POR2 is the workhorse for daily chlorophyll synthesis.

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Response of CO2-starved diatom Phaeodactylum tricornutum to light intensity transition.

Publications

Response of CO<sub>2</sub>-starved diatom <i>Phaeodactylum tricornutum</i> to light intensity transition.

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