 |
| Titel |
Calcification and inorganic carbon uptake in the coccolithophore Emiliania huxleyi |
| VerfasserIn |
L. C. M. Mackinder, L. T. Bach, K. G. Schulz, G. Wheeler, D. C. Schroeder, C. Brownlee, U. Riebesell |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065608
|
|
|
|
|
|
| Zusammenfassung |
| Calcification in the coccolithophore Emiliania huxleyi is a tightly regulated process requiring
the intracellular transport of Ca2+ and inorganic carbon. The presented work focuses on the
mechanisms of calcification in E. huxleyi identifying key genes involved in Ca2+ and
dissolved inorganic carbon (DIC) transport. An initial experiment involving the removal of
Ca2+ from the culture medium to stop calcite formation supports previous data that
photosynthesis has no mechanistic dependence on calcification with organic carbon fixation
rates maintained in the absence of Ca2+. Monitoring gene expression identified several key
genes putatively involved in calcification with Ca2+ removal resulting in a “non-calcifying”
gene expression profile. In a series of separate experiments the importance of the
individual components of the carbonate system (CO2, HCO3-, CO32- and pH) on
coccolithophore calcification and photosynthesis were investigated. To disentangle the
carbonate system E. huxleyi was cultured at constant CO2 and constant pH and various
physiological parameters including calcification, organic carbon fixation and growth
rates were measured. In conjunction the transcriptional response of E. huxleyi was
also analysed with the gene expression of multiple genes putatively involved in
inorganic carbon transport and pH homeostasis profiled. The data strongly supports that
HCO3- is the principle substrate for calcification and growth and organic carbon
fixation rates are primarily influenced by CO2with pH also playing a key role at lower
values. The transcriptional analyses of multiple genes show that a putative HCO3-
transporter, four putative H+ transporters, and three carbonic anhydrases remained
largely unaffected at high DIC concentrations but are significantly up-regulated at
low concentrations. This transcriptional profile supports the presence of a carbon
concentrating mechanism (CCM) in E. huxleyi and provides, for the first time, the
genetic basis of a CCM in a haptophyte algae. Results presented here indicate that
the removal of calcification does not reduce photosynthesis and that potentially at
very low DIC availability calcification is sacrificed to allow the reallocation of
intracellular inorganic carbon from calcite to organic carbon. The understanding of the
calcification process and the influence of changing carbonate chemistry on E. huxleyi are
needed to comprehend how this species could respond to environmental change. |
|
|
|
|
|
|