Trafficking of Silaffins and Cingulins and Quantification of Underlying Transport Mechanisms

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Diatoms are a group of unicellular phototrophs. One of the cellular hallmarks of these ecologically very important organisms is their silica based cell wall. For Thalassiosira pseudonana, the model organism for the work that is proposed here, genomic data as well as molecular tools for manipulating the genome and expression of genes are well established. This has enabled to study proteins involved in silica generation, such as silaffins, cingulins or silacidins, in vivo. Here we shall to investigate the targeting of three representatives of the silaffin and cingulin families. These proteins are located in different parts of the cell wall (either valve or girdle band) and the molecular signals responsible for that will be studied. After identification, the signals will be investigated for their capacity to redirect a valve protein into the girdle band and vice versa, which is an important step to re-design the cell wall of diatoms. To reveal the cellular machinery for intracellular trafficking of cell wall generation factors, we will study marker proteins, which are expected to be part of this process, in a proteomics approach. In parallel cis-acting sequences involved in silicon-induced transcriptional regulation will be analyzed. Altogether, our programme will highlight the targeting mechanisms of organic matrix components required to reach the silica cell wall of diatoms.