Photo-Oxidative Stress in Chloroplasts and Molecular Dynamics of Thylakoids
This Special Focus Issue (Vol. 55, Issue 7) was organised by Yasusi Yamamoto, Yuichiro Takahashi and Jian-Ren Shen, and showcases advances in a fascinating emerging field of photosynthetic research: Photo-oxidative stress in chloroplasts and thylakoid membrane dynamics.
Unraveling the Molecular Dynamics of Thylakoids under Light Stress
Yasusi Yamamoto, Yuichiro Takahashi and Jian-Ren Shen
Yamamoto et al. introduce three review papers and eight original research articles as part of this Special Focus Issue describing the latest exciting research on the effects of light stress on chloroplasts and associated changes in thylakoid membrane structure and dynamics.
Quality Control of Photosystem II: Behavior of Photosystem II in the Highly Crowded Grana Thylakoids under Excessive Light
Yasusi Yamamoto, Suguru Kai, Atsuki Ohnishi, Nodoka Tsumura, Tomomi Ishikawa, Haruka Hori, Noriko Morita and Yasuo Ishikawa
Plant exposure to high light leads to protein aggregation within the crowded photosystem II (PSII)/light-harvesting complex II (LHCII) subunits of chloroplast thylakoids. Two types of aggregation occur: (1) reversible aggregation of LHCII and (2) irreversible aggregation (cross-linking) of the PSII core subunits. In this review, the occurrence of protein aggregation in spinach thylakoids and its physiological significance in avoidance and tolerance of light stress is explained, as well as its relationship with light-induced structural changes of thylakoids.
This paper reviews various methods to directly detect singlet oxygen ( 1 O 2 ) formation by an isolated photosynthetic pigment protein complex first introduced by Telfer and colleagues in the 1990s. The techniques are now used as a standard procedure to measure 1 O 2 formation induced by stress treatment of plants and algae. Current research into 1 O 2 as an important signaling molecule triggering gene expression of proteins involved in plant protection, particularly against light stress damage, is also discussed.
The Role of Metals in Production and Scavenging of Reactive Oxygen Species in Photosystem II
Pavel Pospíšil
In this review, Pospíšil discusses the metal chemistry of photosystem II, which contains three metal centers comprising: non-heme iron, heme iron of cytochrome b 559 and the water-splitting manganese complex. These metal centers share both pro-oxidant and antioxidant properties, however, it is the balance between the formation and elimination of reactive oxygen species formed by PSII metal centers that is crucial for the prevention of photo-oxidative damage.
Identification of Oxidatively Modified Proteins in Salt-Stressed Arabidopsis: A Carbonyl-Targeted Proteomics Approach
Jun'ichi Mano, Mitsuaki Nagata, Shoutarou Okamura, Takeshi Shiraya and Toshiaki Mitsui
The modification of proteins by reactive oxygen species (ROS) and lipid peroxide-derived reactive carbonyl species (RCS) is responsible for oxidative injury in cells. In this work, Mano and colleagues identified 39 proteins that were modified by RCS or ROS in salt-stressed Arabidopsis leaves. The obtained list of RCS- and ROS-target proteins will provide clues about the biochemical processes that take place during stress response and damage in plants.
Significance Of The Photosystem II Core Phosphatase PBCP For Plant Viability And Protein Repair In Thylakoid Membranes
Sujith Puthiyaveetil, Timothy Woodiwiss, Ryan Knoerdel, Ahmad Zia, Magnus Wood, Ricarda Hoehner and Helmut Kirchhoff
The significance of dephosphorylation of the water-splitting photosystem II (PSII) complex by a recently discovered PSII Core Phosphatase (PBCP) for PSII repair is unknown. By studying Arabidopsis PBCP knockout mutants, Puthiyaveetil et al. discovered that this phosphatase affects growth characteristics of the plant and shows impaired degradation of the central D1 subunit of PSII. These results indicate that dephosphorylation of PSII subunits is required for efficient D1 degradation.
Quality Control of Photosystem II: Direct Imaging of the Changes in the Thylakoid Structure and Distribution of FtsH Proteases in Spinach Chloroplasts under Light Stress
Miho Yoshioka-Nishimura, Daisuke Nanba, Takashi Takaki, Chikako Ohba, Nodoka Tsumura, Noriko Morita, Hirotaka Sakamoto, Kazuyoshi Murata and Yasusi Yamamoto
Both migration of photodamaged D1 protein from the grana to the grana margins or stroma thylakoids, and access of the specific protease FtsH to D1 are essential for repairing photosystem II during light stress. This paper presents quantitative analyses of TEM images and 3D modeling to demonstrate that thylakoid unstacking occurs at the grana margins and that changes in thylakoid stacking take place, respectively, after strong illumination of spinach leaves. The data thus imply that structural changes of the thylakoids also aid the PSII repair process.
Requirement of Asparagine 298 on D1 Protein for Oxygen Evolution: Analyses by Exhaustive Amino Acid Substitution in the Green Alga Chlamydomonas reinhardtii
Hiroshi Kuroda, Natsumi Kodama, Xiao-Yu Sun, Shin-ichiro Ozawa and Yuichiro Takahashi
The role played by the hydrogen bond network located near the oxygen-evolving Mn 4 CaO 5 cluster and the lumenal bulk of photosystem II is unclear. Kuroda et al. generated mutants in which Asn-298 in protein D1 of the network was substituted by each of the other 19 different amino acid residues. In all mutants, oxygen-evolving activity was significantly impaired, indicating that this Asn-298 is functionally important. Further analyses of these mutants will reveal how the hydrogen bond network is required for O 2 evolution.
Investigating the Photoprotective Role of Cytochrome b-559 in Photosystem II in a Mutant with Altered Ligation of the Haem
Mary L. Hamilton, Emanuel Franco, Zsuzsanna Deák, Eberhard Schlodder, Imre Vass and Peter J. Nixon
Cytochrome b- 559 is a ubiquitous component of the oxygen-evolving photosystem II (PSII) complex but its physiological role is still unclear. In this paper, a chloroplast mutant with altered ligation of the haem was constructed in the green alga Chlamydomonas reinhartdtii . From their analysis, the authors conclude that the cytochrome optimises electron transfer on the acceptor side of PSII and that it plays multiple roles in the photoprotection of PSII; from the prevention of damage to the optimisation of assembly during PSII repair.
Physiological Functions of PsbS-Dependent and -Independent NPQ under Naturally Fluctuating Light Conditions
Masahiro Ikeuchi, Nozomu Uebayashi, Fumihiko Sato and Tsuyoshi Endo
The amount of energy lost in photosystem II (PSII) through thermal dissipation associated with its PsbS subunit under natural light has not been quantified. Analyses of energy allocation within PSII in PsbS-suppressed rice transformants revealed that PsbS-dependent energy loss was significant at the induction phase of photosynthesis as well as under field conditions. The results suggest that PsbS plays an important photoprotective role under field conditions, by minimizing uncontrollable dissipation S f,D and S slow .
Membrane Crystals Of Plant Light-harvesting Complex II Disassemble Reversibly In Light
Geoffrey Hind, Joseph S. Wall, Zsuzsanna Várkonyi, Anita Istokovics, Petar H. Lambrev and Gy?z? Garab
Structural flexibility of the photosynthetic antenna system of plants is implied by its functional flexibility in performing photochemistry under low light, and thermal dissipation under high light intensities. Scanning transmission electron microscopy of unstained, unfixed membrane crystals of isolated antenna complexes (LHCIIs) showed that light drives their dark-reversible disaggregation. Similar reorganizations in thylakoid membranes, detected earlier by spectroscopy, are consistent with the photoprotective role of these processes in vivo.
Transcriptional Regulation of the Stress-Responsive Light Harvesting Complex Genes in Chlamydomonas reinhardtii
Shinichiro Maruyama, Ryutaro Tokutsu and Jun Minagawa
Light energy dissipation is critical for photosynthetic organisms, yet regulation of the genes involved in this process has been elusive to date. Maruyama et al. reveal that transcription of the three stress-responsive light harvesting complex (LHCSR) genes is tightly coupled with photosystem and calmodulin activities in Chlamydomonas . These data imply a complex signaling network for light energy dissipation.