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Transcriptomic responses of Emiliania huxleyi to Ocean Acidification

This study examines the transcriptomic responses of Emiliania huxleyi, a coccolithophore, to ocean acidification. It evaluates the effects of different CO2 levels and pH on gene expression, carbon metabolism, light physiology, signaling, and ion fluxes. The findings show a shift in carbon fluxes, increased energy efficiency, and altered cellular signaling under ocean acidification conditions.

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Transcriptomic responses of Emiliania huxleyi to Ocean Acidification

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  1. Transcriptomic responsesof Emiliania huxleyito Ocean Acidification Sebastian D. Rokitta, Uwe John and Björn Rost

  2. OceanAcidifcation 35 30 25 20 15 10 5 0 [CO2] pHSWS [DIC] [µmol kg-1] [CO32-] 8.2 2400 [µmol kg-1] pH 2000 300 8.1 DIC 1600 250 1200 8.0 200 CO32- 800 150 7.9 400 100 0 7.8 CO2 50 0 1850 1900 1950 2000 2050 2100 Year After Wolf-Gladrow et al. (1999)

  3. Coccolithophores • Photo: NASA, PML

  4. Biological carbonpumps

  5. OA-responses in E. huxleyi Modifiedfrom Hoppe et al. (2011)

  6. Energization?

  7. The matrixapproach • Light vs. pCO2 • 380 µatm 1000 µatm • Acclimationdata (µ, POC, PIC) • Physiology (Ciacquisition, lightreactions) • Transcriptomics (geneexpression) • 50 µmolphotons m-2 s-1 • 300 µmolphotons m-2 s-1

  8. PhenomenologyRokitta & Rost (2012) • PIC productiondrops (especiallyunderlowlight!) • POC productionisboosted (especiallyunderlowlight!) • TPC productionisinsensitive

  9. PhysiologyRokitta & Rost (2012) • More POC despitelesspigmentationand O2evolution  Improvedenergyefficiencyunder OA

  10. Gene expression?

  11. Transcriptomics OA responsive genes 1172 ↑ Low-light acclimation 861 ↓ 1082↑ High-light acclimation 814 ↓

  12. Transcriptomics Low-light specific 447 ↑ 725 ↑ 236 ↓ 625 ↓ Core OA-response High-light specific 357 ↑ 189 ↓

  13. Transcriptomics Core OA-response LL specific OA-response HL specific OA-response Carbonmetabolism Light physiology Signalling Ion fluxes # of genes; signdenotesregulation(+ ↑; - ↓) • Pentosephosphatepathway ↑ • Glycolysis ↓ • Regulation of C fluxes ↑ Organellar shuttling↑ -40 -40 -40 -20 -20 -20 0 0 0 20 20 20 40 40 40 • FattyAcid & Glucan anabolism↑ • Energydissipation↑ • Energydissipation↑ • Lipid and IP3signaling↑ • Membrane potentials↑

  14. OA re-wirescarbonfluxes NADPH NADH

  15. OA affectsthe redox hub NADP/NADPH NAD/NADH GSH Mitochon-drium Ca2+ ROS Asc Carbonmetabolism Chloro-plast Trx ROS XC EMS ... ROS Ca2+

  16. Conclusions • OA causes a shuntingofcarbonfrom calcification towardsbiomassproduction • OA-Responses aremodulatedbyenergyavailabilityandtypicallyattenuatedbyhighlight • OA affectscellularsignalingandtheredox hub andtherebyre-wirescarbonfluxnetworks

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