OCEANIA

We recently discovered a protein from the model marine diatom, Thalassiosira pseudonana, that belongs to a new subclass of carbonic anhydrase, iota-CA. We showed that this protein is involved in CO2-concentrating mechanisms and uses Mn2+ as a co-factor instead of Zn2+. Since we also showed that iota-CA is present in other marine diatoms and is widespread in the ocean, it could have a significant role in global biogeochemical cycling. The use of Mn2+ instead of Zn2+ may reflect its availability or affect the enzyme properties. The overarching scientific objective of this project is to elucidate the role of iota-CA in photosynthesis of marine diatoms, extending the analysis to a contrasting diatom, Phaeodactylum tricornutum, where the use of genetic tools are better established. This objective will be achieved within 3 workpackages combining a range of in vitro and in vivo methods. The aim of workpackage 1 is to unravel the detailed molecular mechanisms of the function, and architecture of iota-CA from the information yielded by its protein structure using a combination of structural, biophysical and biochemical methods. The aim of workpackage 2 is to elucidate the catalytic mechanisms of iota-CA, and the role of Mn2+ instead of Zn2+. The aim of the third workpackage is to determine the effect of iota-CA inactivation on diatoms growth and physiology using genetic engineering tools and proteomic analyses, to determine the contribution of iota-CA to the metabolism of the diatoms.