Transcriptomic responses of Emiliania huxleyi

Transcriptomic responses of Emiliania huxleyi

to Ocean Acidification

Sebastian D. Rokitta, Uwe John and Björn Rost

Ocean Acidifcation

CO₂ pH DIC

Year

[CO₃^2-]

300 250

150 100 50 0 200

1850 1900 1950 2000 2050 2100

pH_SWS

7.8 8.2

8.1

8.0

7.9

2400

1600 1200 800 400 2000

0

[DIC]

[μmol kg^-1]

CO₃^2-

[CO₂]

35 30

20 15

5 0 25

10

[μmol kg^-1]

After Wolf-Gladrow et al. (1999)

Photo: NASA, PML

Coccolithophores

Biological carbon pumps

OA-responses in E. huxleyi

Modified from Hoppe et al. (2011)

Energization?

The matrix approach

Light vs. pCO₂

50 μmol photons m^-2 s^-1

300 μmol photons m^-2 s^-1

380 ^μatm 1000 ^μatm

• Acclimation data (μ, POC, PIC)

• Physiology (C

acquisition, light reactions)

• Transcriptomics (gene expression)

Phenomenology

• PIC production drops

(especially under low light!)

• POC production is boosted (especially under low light!)

• TPC production is insensitive

Physiology

• More POC despite less pigmentation and O₂ evolution

 Improved energy efficiency under OA

Gene expression?

Transcriptomics

Low-light acclimation

1172 ↑ 861 ↓

High-light

acclimation 1082↑

814 ↓

OA responsive genes

Low-light specific

447 ↑ 236 ↓

High-light specific

357 ↑ 189 ↓ 725 ↑

625 ↓ Core

OA-response

Transcriptomics

# of genes; sign denotes regulation (+ ↑; - ↓)

Carbon metabolism Light physiology Signalling Ion fluxes

Core OA-response

LL specific OA-response

HL specific OA-response

-40 -20 0 20 40 -40 -20 0 20 40 -40 -20 0 20 40

Organellar shuttling ↑ Pentose phosphate pathway ↑

Glycolysis ↓

Fatty Acid & Glucan anabolism↑ Energy dissipation ↑

Lipid and IP₃ signaling ↑ Membrane potentials ↑

Regulation of C fluxes ↑

Energy dissipation ↑

Transcriptomics

OA re-wires carbon fluxes

NADPH NADH

OA affects the redox hub

Carbon

metabolism ^Trx

XC Asc GSH

Chloro- plast

EMS

NADP/NADPH NAD/NADH

...

Mitochon- drium

Conclusions

• OA causes a shunting of carbon from

calcification towards biomass production

• OA-Responses are modulated by energy

availability and typically attenuated by high light

• OA affects cellular signaling and the redox hub and thereby re-wires carbon flux networks