DNA-Specific DAPI Staining of the Pyrenoid Matrix During its Fission in Dunaliella salina (Dunal) Teodoresco (Chlorophyt
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DNA‑Specific DAPI Staining of the Pyrenoid Matrix During its Fission in Dunaliella salina (Dunal) Teodoresco (Chlorophyta) Anna A. Oleksienko1 · Yurii G. Kot1 · Victoria P. Komaristaya1 Received: 28 November 2019 / Accepted: 3 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The algal pyrenoid is a naked phase-separated liquid compartment inside the chloroplast consisting predominantly of densely packaged Rubisco and most often transversed by a system of lipid membranes. The pyrenoid participates in carbon-concentrating mechanisms of algae. During the cell division, the daughter cells of algae acquire the pyrenoids via their assembly or fission, the mechanisms of which are not fully understood. We suppose that the chloroplast nucleoid scaffolds the new pyrenoid like the cyanobacterial nucleoid positions carboxysomes before the cell division. This work was aimed at visualization and localization of the chloroplast DNA relative to the pyrenoid in synchronously dividing cells of Dunaliella salina with DNA-specific fluorescent DAPI stain through the fluorescent confocal microscope. The intense DNA-specific blue DAPI fluorescence was discovered in the pyrenoids matrix under the starch shell in the presumably pre-mitotic cells, during and following the pyrenoid fission. In the interphase cells, the chloroplast DNA localized both in the pyrenoid core and in several small nucleoids on the outer surface of the starch shell around the pyrenoid. The observations were compared with the literature data on the same and other algal species. The spatial pre-requisite exists in D. salina for the chloroplast nucleoid to scaffold the pyrenoid fission. A potential alternative explanation was declared being the algal pyrenoid as the chloroplast genetic center. The theoretical and practical implications of the findings were discussed.
Introduction The chloroplast origin and evolution constitute one of the fundamental problems in cell biology. The pyrenoid is a chloroplast compartment of many species of almost all eukaryotic algal lineages lacking in land plants. The exception is some hornworts, the group, which is closely related to land plant ancestors [50]. In the green plants, the chloroplasts are believed to have originated from endosymbiont ancient cyanobacteria engulfed by a proto-eukaryotic cell [46]. In cyanobacteria, cytoplasm microcompartments called carboxysomes present a functional equivalent of the algal pyrenoid [4]. Lack of the pyrenoid in some eukaryotic algae and land plants can be viewed upon as a loss of function in * Victoria P. Komaristaya [email protected] Anna A. Oleksienko [email protected] Yurii G. Kot [email protected] 1
The School of Biology, V.N. Karazin Kharkiv National University, Svobody sq., 4, Kharkiv 61022, Ukraine
the evolution from a free-living photosynthetic prokaryote to a semi-autonomous eukaryotic organelle. New insights on structure, function, and mechanisms of transmission from generation to generation of the algal pyrenoids
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