Dissecting the Native Architecture and Dynamics of Cyanobacterial Photosynthetic Machinery

Abstract

The structural dynamics and flexibility of cell membranes play fundamental roles in the functions of the cells, i.e., signaling, energy transduction, and physiological adaptation. The cyanobacterial thylakoid membrane represents a model membrane that can conduct both oxygenic photosynthesis and respiration simultaneously. In this study, we conducted direct visualization of the global organization and mobility of photosynthetic complexes in thylakoid membranes from a model cyanobacterium, Synechococcus elongatus PCC 7942, using high-resolution atomic force, confocal, and total internal reflection fluorescence microscopy. We visualized the native arrangement and dense packing of photosystem I (PSI), photosystem II (PSII), and cytochrome (Cyt) b6f within thylakoid membranes at the molecular level. Furthermore, we functionally tagged PSI, PSII, Cyt b6f, and ATP synthase individually with fluorescent proteins, and revealed the heterogeneous distribution of these four photosynthetic complexes and determined their dynamic features within the crowding membrane environment using live-cell fluorescence imaging. We characterized red light-induced clustering localization and adjustable diffusion of photosynthetic complexes in thylakoid membranes, representative of the reorganization of photosynthetic apparatus in response to environmental changes. Understanding the organization and dynamics of photosynthetic membranes is essential for rational design and construction of artificial photosynthetic systems to underpin bioenergy development. Knowledge of cyanobacterial thylakoid membranes could also be extended to other cell membranes, such as chloroplast and mitochondrial membranes.

Protein arrangement factor: a new photosynthetic parameter characterizing the organization of thylakoid membrane proteins

“…In addition to confocal microscopic methods, this spatial heterogeneity in thylakoid membranes has been reported also by proteomics or electron and atomic force microscopy (Sherman et al , Agarwal et al , Collins et al , MacGregor‐Chatwin et al ). The heterogeneity has been often studied during a short period of high‐light (HL) stress (Sarcina et al , Steinbach and Kana , Casella et al , Strašková et al ). The data suggested a slight re‐arrangement (Sarcina et al , Casella et al ) or instability (Steinbach and Kana , Strašková et al ) of the thylakoid membrane organization during few minutes of irradiation on the level of a single cell.…”

“…The heterogeneity has been often studied during a short period of high‐light (HL) stress (Sarcina et al , Steinbach and Kana , Casella et al , Strašková et al ). The data suggested a slight re‐arrangement (Sarcina et al , Casella et al ) or instability (Steinbach and Kana , Strašková et al ) of the thylakoid membrane organization during few minutes of irradiation on the level of a single cell. There are more detailed bulk measurements with cell suspensions.…”

“…Even though the heterogeneous arrangement of photosystems in plant thylakoids has been demonstrated (Andersson and Anderson 1980, Albertsson 2001, Ruban and Johnson 2015, their spatial distribution in cyanobacteria is still not fully resolved. Heterogeneity of PPCs in Synechocystis thylakoid membranes has been proposed to exist based on confocal microscopy studies (Casella et al 2017, Grigoryeva and Chistyakova 2018, Strašková et al 2019. Time-lapse confocal imaging of single cells suggested both dynamic (Sarcina et al 2006, Casella et al 2017 or rather static behavior of these heterogeneous structures in minutes time scale (Strašková et al 2019).…”

“…Heterogeneity of PPCs in Synechocystis thylakoid membranes has been proposed to exist based on confocal microscopy studies (Casella et al 2017, Grigoryeva and Chistyakova 2018, Strašková et al 2019. Time-lapse confocal imaging of single cells suggested both dynamic (Sarcina et al 2006, Casella et al 2017 or rather static behavior of these heterogeneous structures in minutes time scale (Strašková et al 2019).…”

“…Long-term acclimation involves compositional, functional and structural changes of thylakoid protein complexes (Oquist et al 1995, Muramatsu et al 2009, Allahverdiyeva et al 2015, Majumder et al 2017. All these changes detected during bulk measurements (short and long term) must be, to some extent, mirrored in the microscopic localization of fluorescent PPCs and its change during irradiation (Sarcina et al 2006, Steinbach and Kana 2016, Casella et al 2017.…”