Auxiliary functions in photosynthesis: the role of the FtsH protease

2001 ◽  
Vol 29 (4) ◽  
pp. 455-459 ◽  
Author(s):  
S. Bailey ◽  
P. Silva ◽  
P. Nixon ◽  
C. Mullineaux ◽  
C. Robinson ◽  
...  
Keyword(s):  
Molecular Chaperones ◽  
Protein Targeting ◽  
Photosynthetic Apparatus ◽  
Oxygenic Photosynthesis ◽  
Turnover Rates ◽  
Dynamic Nature ◽  
Auxiliary Functions ◽  
Zinc Metalloprotease ◽  
Ftsh Protease

Oxygenic photosynthesis can be described effectively by using two long-standing models: the Z-scheme and the chemiosmotic hypothesis. However, these models do not reveal the dynamic nature of the thylakoid membrane and the four major complexes that it binds. The composition of the photosynthetic apparatus is continually changing in response to a range of environmental stimuli. In addition, many photosynthetic components have some of the highest turnover rates in Nature. Changes in composition and turnover of photosynthetic components require the degradation of existing and damaged polypeptides and the resynthesis and co-ordinated assembly of new polypeptides and their associated cofactors. This is achieved by several auxiliary functions, including proteolysis, protein targeting and the action of molecular chaperones. Some of the components involved in these functions, such as translocons, chaperones and proteases, have been identified but many of the auxiliary functions of photosynthesis remain uncharacterized. Among the proteases known to be associated with the thylakoids is the zinc metalloprotease FtsH, which might also act as a chaperone. Here we provide an overview of the thylakoid FtsH protease and discuss its role in the maintenance and assembly of the photosynthetic apparatus.

scholarly journals Overexpression of plastid terminal oxidase in Synechocystis sp. PCC 6803 alters cellular redox state

2017 ◽  
Vol 372 (1730) ◽  
pp. 20160379 ◽  
Author(s):  
Kathleen Feilke ◽  
Ghada Ajlani ◽  
Anja Krieger-Liszkay
Keyword(s):  
Higher Plants ◽  
Photosynthetic Apparatus ◽  
Oxygenic Photosynthesis ◽  
Terminal Oxidase ◽  
Cellular Redox ◽  
Excess Electrons ◽  
Plastid Terminal Oxidase ◽  
Absorption Measurements ◽  
Pcc 6803

Cyanobacteria are the most ancient organisms performing oxygenic photosynthesis, and they are the ancestors of plant plastids. All plastids contain the plastid terminal oxidase (PTOX), while only certain cyanobacteria contain PTOX. Many putative functions have been discussed for PTOX in higher plants including a photoprotective role during abiotic stresses like high light, salinity and extreme temperatures. Since PTOX oxidizes PQH 2 and reduces oxygen to water, it is thought to protect against photo-oxidative damage by removing excess electrons from the plastoquinone (PQ) pool. To investigate the role of PTOX we overexpressed rice PTOX fused to the maltose-binding protein (MBP-OsPTOX) in Synechocystis sp. PCC 6803, a model cyanobacterium that does not encode PTOX. The fusion was highly expressed and OsPTOX was active, as shown by chlorophyll fluorescence and P 700 absorption measurements. The presence of PTOX led to a highly oxidized state of the NAD(P)H/NAD(P) + pool, as detected by NAD(P)H fluorescence. Moreover, in the PTOX overexpressor the electron transport capacity of PSI relative to PSII was higher, indicating an alteration of the photosystem I (PSI) to photosystem II (PSII) stoichiometry. We suggest that PTOX controls the expression of responsive genes of the photosynthetic apparatus in a different way from the PQ/PQH 2 ratio. This article is part of the themed issue ‘Enhancing photosynthesis in crop plants: targets for improvement’.

scholarly journals Antioxidant and Signaling Role of Plastid-Derived Isoprenoid Quinones and Chromanols

2021 ◽  
Vol 22 (6) ◽  
pp. 2950
Author(s):  
Beatrycze Nowicka ◽  
Agnieszka Trela-Makowej ◽  
Dariusz Latowski ◽  
Kazimierz Strzalka ◽  
Renata Szymańska
Keyword(s):  
Current Knowledge ◽  
Stress Factors ◽  
Oxygenic Photosynthesis ◽  
Ros Generation ◽  
Main Site ◽  
Storage Lipids ◽  
Abiotic Stress Factors ◽  
Cell Components ◽  
And Function

Plant prenyllipids, especially isoprenoid chromanols and quinols, are very efficient low-molecular-weight lipophilic antioxidants, protecting membranes and storage lipids from reactive oxygen species (ROS). ROS are byproducts of aerobic metabolism that can damage cell components, they are also known to play a role in signaling. Plants are particularly prone to oxidative damage because oxygenic photosynthesis results in O2 formation in their green tissues. In addition, the photosynthetic electron transfer chain is an important source of ROS. Therefore, chloroplasts are the main site of ROS generation in plant cells during the light reactions of photosynthesis, and plastidic antioxidants are crucial to prevent oxidative stress, which occurs when plants are exposed to various types of stress factors, both biotic and abiotic. The increase in antioxidant content during stress acclimation is a common phenomenon. In the present review, we describe the mechanisms of ROS (singlet oxygen, superoxide, hydrogen peroxide and hydroxyl radical) production in chloroplasts in general and during exposure to abiotic stress factors, such as high light, low temperature, drought and salinity. We highlight the dual role of their presence: negative (i.e., lipid peroxidation, pigment and protein oxidation) and positive (i.e., contribution in redox-based physiological processes). Then we provide a summary of current knowledge concerning plastidic prenyllipid antioxidants belonging to isoprenoid chromanols and quinols, as well as their structure, occurrence, biosynthesis and function both in ROS detoxification and signaling.

The role of carbonic anhydrase α-CA4 in the adaptive reactions of photosynthetic apparatus: the study with α-CA4 knockout plants

PROTOPLASMA ◽  
2019 ◽  
Vol 257 (2) ◽  
pp. 489-499 ◽  
Author(s):  
Natalia N. Rudenko ◽  
Tatyana P. Fedorchuk ◽  
Vasily V. Terentyev ◽  
Olga V. Dymova ◽  
Ilya A. Naydov ◽  
...  
Keyword(s):  
Carbonic Anhydrase ◽  
Photosynthetic Apparatus ◽  
Adaptive Reactions

scholarly journals Possible Role of Peroxynitrite in the Responses Induced by Fusicoccin in Plant Cultured Cells

Plants ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 182 ◽  
Author(s):  
Massimo Malerba ◽  
Raffaella Cerana
Keyword(s):  
Cytochrome C ◽  
Dna Fragmentation ◽  
Stress Responses ◽  
Molecular Chaperones ◽  
Caspase 3 ◽  
Cultured Cells ◽  
Acer Pseudoplatanus ◽  
Cytochrome C Release ◽  
Induced Stress

Fusicoccin (FC) is a well-known phytotoxin able to induce in Acer pseudoplatanus L. (sycamore) cultured cells, a set of responses similar to those induced by stress conditions. In this work, the possible involvement of peroxynitrite (ONOO−) in FC-induced stress responses was studied measuring both in the presence and in the absence of 2,6,8-trihydroxypurine (urate), a specific ONOO− scavenger: (1) cell death; (2) specific DNA fragmentation; (3) lipid peroxidation; (4) production of RNS and ROS; (5) activity of caspase-3-like proteases; and (6) release of cytochrome c from mitochondria, variations in the levels of molecular chaperones Hsp90 in the mitochondria and Hsp70 BiP in the endoplasmic reticulum (ER), and of regulatory 14-3-3 proteins in the cytosol. The obtained results indicate a role for ONOO− in the FC-induced responses. In particular, ONOO− seems involved in a PCD form showing apoptotic features such as specific DNA fragmentation, caspase-3-like protease activity, and cytochrome c release from mitochondria.

scholarly journals Adenofection: A Method for Studying the Role of Molecular Chaperones in Cellular Morphodynamics by Depletion-Rescue Experiments

10.3791/54557 ◽  
2016 ◽  
Author(s):  
Margit Fuchs ◽  
Marie-Chloé Boulanger ◽  
Herman Lambert ◽  
Jacques Landry ◽  
Josée N. Lavoie
Keyword(s):  
Molecular Chaperones

scholarly journals Teasing Apart the Role of the Ribosome and Molecular Chaperones in Cellular Protein Folding

2018 ◽  
Vol 114 (3) ◽  
pp. 414a
Author(s):  
Rayna M. Addabbo ◽  
Matthew D. Dalphin ◽  
Yue Liu ◽  
Miranda F. Mecha ◽  
Silvia Cavagnero
Keyword(s):  
Protein Folding ◽  
Molecular Chaperones ◽  
Cellular Protein

scholarly journals Biochemical and genetic analysis of the role of the viral polymerase in enterovirus recombination

2016 ◽  
Vol 44 (14) ◽  
pp. 6883-6895 ◽  
Author(s):  
Andrew Woodman ◽  
Jamie J. Arnold ◽  
Craig E. Cameron ◽  
David J. Evans
Keyword(s):  
Genetic Recombination ◽  
Evolutionary Process ◽  
Virus Genome ◽  
Biochemical Assay ◽  
Strand Transfer ◽  
Turnover Rates ◽  
Coding Region ◽  
Cis Acting ◽  
Polymerase Fidelity

Abstract Genetic recombination in single-strand, positive-sense RNA viruses is a poorly understand mechanism responsible for generating extensive genetic change and novel phenotypes. By moving a critical cis-acting replication element (CRE) from the polyprotein coding region to the 3′ non-coding region we have further developed a cell-based assay (the 3′CRE-REP assay) to yield recombinants throughout the non-structural coding region of poliovirus from dually transfected cells. We have additionally developed a defined biochemical assay in which the only protein present is the poliovirus RNA dependent RNA polymerase (RdRp), which recapitulates the strand transfer events of the recombination process. We have used both assays to investigate the role of the polymerase fidelity and nucleotide turnover rates in recombination. Our results, of both poliovirus intertypic and intratypic recombination in the CRE-REP assay and using a range of polymerase variants in the biochemical assay, demonstrate that RdRp fidelity is a fundamental determinant of recombination frequency. High fidelity polymerases exhibit reduced recombination and low fidelity polymerases exhibit increased recombination in both assays. These studies provide the basis for the analysis of poliovirus recombination throughout the non-structural region of the virus genome and provide a defined biochemical assay to further dissect this important evolutionary process.

scholarly journals Suffering Silence While Exposed to Workplace Bullying: The Role of Psychological Contract Violation, Benevolent Behavior and Positive Psychological Capital

2020 ◽  
Vol 4 (4) ◽  
pp. 15-54
Author(s):  
Namra Jamshaid ◽  
Sadia Arshad
Keyword(s):  
Psychological Contract ◽  
Workplace Bullying ◽  
Psychological Capital ◽  
Turnover Rates ◽  
Passive Coping ◽  
Psychological Contract Violation ◽  
Current Transition ◽  
Free Environment ◽  
Contract Violation

Becoming impediment to organizational functioning in several ways, the prevalence of workplace bullying costs much to organizations. As in the current transition phase of Pakistan, the intentions to leave doesn’t manifest in actual turnover rates.  Hence the current study is conducted to analyze the passive coping strategies of employees in the face of workplace bullying. It is theorized that the relationship is mediated by psychological contract violation. Moreover, it is predicted that the process of mediation is stronger for individuals who report high levels of benevolent behavior and perceives psychological capital to be low. Data is collected from 359 young doctors and nurses of three government administered hospitals. Results indicate a significant bullying-silence relationship where psychological contract violation plays a role of partial mediator. Moreover, benevolence and PsyCap are powerful moderators to alter the already established relationship. Conclusions of the current study are further elaborated in terms of their practical contribution and future directions. Workplace bullying is an organizational reality. Hence efforts to make an entire bullying-free environment is next to impossible.  So, in addition to make an effort in ending up this maltreatment, managers must limit its consequences by understanding its dynamics. Reduce the bullying culture and save precious resources i.e. potential employees.

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