Chitin synthase localization in the diatom Thalassiosira pseudonana
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(2020) 2:10 Wustmann et al. BMC Mat https://doi.org/10.1186/s42833-020-00016-9
Open Access
RESEARCH ARTICLE
Chitin synthase localization in the diatom Thalassiosira pseudonana Martin Wustmann1, Nicole Poulsen2, Nils Kröger2,3,4 and Karl‑Heinz van Pée1*
Abstract Chitin constitutes an abundant component in many biologically formed minerals (biominerals). While the role of chi‑ tin for the formation and properties of calcium-based biominerals has been extensively studied, little is known about its role in silica-based biominerals. Furthermore, there is hardly any information about the enzyme machinery for chitin biosynthesis in biomineral-forming organisms. Here we have identified a chitin synthase, chs7305, in the diatom Thalassiosira pseudonana. In stationary cells, chs7305 is located specifically in a ring pattern in the region of the silici‑ fied girdle bands. The expression pattern of the chs7305 gene and the co-localization of the encoded enzyme with chitin provides evidence for the importance of chitin synthesis for cell wall function under nutrient limited conditions. Chs7305 is the first chitin synthase that has been localized in a diatom. Keywords: Chitin, Chitin synthase, Thalassiosira pseudonana, Peptide antibody, Immunolocalization Introduction Diatoms are outstanding examples of unicellular organisms capable of forming complex shaped cell walls made of silica [1, 2]. The silica building blocks of the cell wall are produced in a yet little understood morphogenetic process that is believed to involve long chain polyamines (LCPA), unique families of proteins (e.g., silaffins, silacidins), and insoluble organic matrices [3, 4]. Three types of insoluble organic matrices were recently identified as integral components of the silica cell wall of the diatom Thalassiosira pseudonana: meshworks [5], microrings [6] and microplates [7]. The meshworks are chitinbased with proteins as minor components, whereas the microrings and microplates are mainly composed of proteins [5–7]. Many different organisms employ insoluble organic matrices as central components for the biosynthesis of mineralized structures (biomineralization) [8]. The presence of chitin is particularly well studied in CaCO3 biomineralization [8–12]. In nacre it contributes *Correspondence: karl‑[email protected]‑dresden.de 1 General Biochemistry, Technical University of Dresden, 01062 Dresden, Germany Full list of author information is available at the end of the article
to high impact resistance and is believed to influence the process of biomineralization [13, 14]. In some centric diatoms, chitin is present as crystalline β-chitin fibers that are extruded through specialized openings in the cell wall called fultoportulae. These chitin fibers are not involved in silica biomineralization, and instead are believed to slow-down the sinking rate of the photosynthetically active diatom cells by increasing their drag in the water [15–17]. Distinct from the chitin fibers are the chitin meshworks, which are tightly associated with the silica of t
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