Transcriptomic responsesof Emiliania huxleyi

to Ocean Acidification

Sebastian D. Rokitta, Uwe John and Björn Rost

Ocean Acidifcation

CO2

pH

DIC

Year

[CO32-]

300

250

150

100

50

0

200

1850

1900 2100

1950 2050

2000

pHSWS

7.8

8.2

8.1

8.0

7.9

2400

1600

1200800

400

2000

0

[DIC][µmol kg-1]

CO32-

[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 (Ci acquisition, light reactions)• Transcriptomics (gene expression)

Phenomenology Rokitta & Rost

(2012)

• PIC production drops(especially under low light!)

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

• TPC production is insensitive

Physiology Rokitta & Rost

(2012)

• More POC despite less pigmentation and O2 evolution

Improved energy efficiency under OA

Gene expression?

Transcriptomics

Low-lightacclimatio

n

1172 ↑861 ↓

High-lightacclimatio

n

1082↑814 ↓

OA responsive genes

Low-lightspecific

447 ↑236 ↓

High-lightspecific

357 ↑189 ↓

725 ↑625 ↓

CoreOA-

response

Transcriptomics

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

Carbon metabolism

Light physiologySignalling

Ion fluxes

CoreOA-response

LL specificOA-response

HL specificOA-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 metaboli

sm

Trx

XC

Asc

GSH

Chloro-plast

EMS

ROS

ROS

NADP/NADPH

NAD/NADH

...

Mitochon-drium

Ca2+

ROSCa2+

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