Transcriptomic responses of Emiliania huxleyi to Ocean Acidification Sebastian D. Rokitta, Uwe John...

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