Unravelling the Silicification prOcess in RHIzaria through GENetics and Skeletal growth

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Silicon (Si) is a major nutrient in the global ocean, required for growth by a variety of distantly related organisms, including microalgae, sponges and rhizarians. Silicifying Rhizaria were among the first protists to inhabit the ocean and, together with sponges, dominated the biogenic silica production during the Cambrian era. These organisms became an important, though poorly understood, component of marine ecosystems. In the contemporary ocean, diatoms are thought to dominate the planktonic realm and to be the main contributor to the Si cycle. However, my recent work has revealed that Rhizaria have unexpectedly high individual Si production rates and biogenic silica content, suggesting that their contribution to marine Si and carbon cycles may have been underestimated. This project aims to elucidate the process of silicification in Rhizaria and determine sources of variability in silicic acid uptake of these protists, through three tailored work packages (WPs). The first WP, consists of the analyse of transcriptomic data at a global scale as well as individual transcriptomes of isolated Rhizaria to assess the diversity of Si transporters. Thereafter, the examination of silica deposition, using a fluorescence compound, in a broad range of Rhizaria and varying ambient silicic acid concentrations. The final WP, will be the quantification of gene expression during silicification processes using primers designed within WP1. This highly interdisciplinary project combines bioinformatics, molecular biology and physiology, leading to a more unified approach to plankton research. The outcomes of this project will improve our general understanding of Si transport in Rhizaria as well as our understanding of the biogeochemical cycling of Si in the ocean. This work will also constitute a major advance in my career, as I acquire skills in new research methods beyond my current capacity, and build a unique skillset that will set me ahead of the current rhizarian research scope.