Studying the targeting of frustule-associated proteins in the centric diatom Thalassiosira pseudonana
Diatoms are unicellular and photosynthetic organisms of highest ecological relevance. They are very well known because of their ability to exploit the dissolved silica available in the water to synthetize a modified cell wall, called the frustule. The frustule has a specific morphology for each spec...
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|Summary:||Diatoms are unicellular and photosynthetic organisms of highest ecological relevance. They are very well known because of their ability to exploit the dissolved silica available in the water to synthetize a modified cell wall, called the frustule. The frustule has a specific morphology for each species, and its formation process is complex and strictly intertwined with cell division, and therefore with the cell cycle. The diatom T. pseudonana has a strongly silicified frustule and is the first diatom species whose genome was sequenced, in 2004; since then, it has been the subject of many biomineralization studies and several proteins involved in the formation of the frustule, such as the silaffins and the cingulins, have been described, characterized, and localized in vivo. These proteins are believed to enter the secretory pathway at the ER, from which are then transported via vesicles to the Golgi, and from there to the silica deposition vesicle (SDV). When the synthesis of the frustule components inside the SDV is completed, its content is exocytosed outside of the cell. The only published study on the targeting of frustule proteins in T. pseudonana had identified short stretches of amino acids called pentalysine clusters (PLC) as potential targeting signal to the frustule of silaffins. Here, I have investigated the targeting of two cingulin representatives (CinW2 and CinY2) and one silaffins (Sil3) following different approaches: first, I have studied whether the presence of PLC-like regions in cingulins (called lysine-enriched regions (or LERs)) indicate that these regions play a similar role as it was for the PLC of silaffins; I have also studied if it was possible to identify a clear valve- or girdle band-targeting signal and, in that case, if this signal could be used to direct a valve-protein to the girdle or vice versa; second, since there is a remarkable difference in the gene expression between frustule-associated protein-encoding genes, I have investigated if the transcriptional regulation of the genes can affect the targeting of the encoded proteins; in parallel, I have obtained preliminary results regarding the isolation of the promoters of sil3, cinW2, cinY2. Additionally, I have identified unknown frustule proteins based on the presence of a PLC-like regions as well as a new discovered motif.|
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