Protein Arrangement (PA) factor

Konert, G and Steinbach, Gábor and Canonico, M and Kaňa, Radek (2019) Protein Arrangement (PA) factor. PHYSIOLOGIA PLANTARUM, 166 (1). pp. 264-277. ISSN 0031-9317

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Abstract

A proper spatial distribution of photosynthetic pigment-protein complexes - PPCs (photosystems, light-harvesting antennas) is crucial for photosynthesis. In plants, photosystems (PSI and PSII) are heterogeneously distributed between granal and stromal thylakoids. Here we have described similar heterogeneity in the PSI, PSII, and Phycobilisomes (PBS) distribution in cyanobacteria thylakoids into microdomains by applying a new image processing method suitable for the Synechocystis sp. PCC6803 strain with YFP-tagged PSI. The new image processing method is able to analyze fluorescence ratios of PPCs on single cell level, pixel per pixel. Each cell pixel is plotted in CIE1931 color space by forming a pixel-color distribution of the cell. The most common position in CIE1931 is then defined as protein arrangement (PA) factor with x-y coordinates. The PA-factor represents the most abundant fluorescence ratio of PSI/PSII/PBS, the "mode color" of studied cell. We proved that a shift of the PA-factor from the center of the cell-pixel distribution (the "median" cell color) is an indicator of the presence of special subcellular microdomain(s) with a unique PSI/PSII/PBS fluorescence ratio in comparison to other parts of the cell. Further, during a 6 hour high-light (HL) treatment, "median" and "mode" color (PA-factor) of the cell changed similarly on the population level, indicating that such microdomains with unique PSI/PSII/PBS fluorescence were not formed during HL (i.e. fluorescence changed equally in the whole cell). However, the PA-factor was very sensitive in characterizing fluorescence ratios of PSI/PSII/PBS in cyanobacterial cells during HL by depicting a 4-phase acclimation to HL and their physiological interpretation has been discussed. This article is protected by copyright. All rights reserved.

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